Chemistry Honors Midterm – Flashcards
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An electron in a 3d orbital could have which of the following quantum numbers?
1. n = 2; ℓ = 2; mℓ = 2
2. n = 3; ℓ = 2; mℓ = −3
3. n = 3; ℓ = 3; mℓ = 1
4. n = 3; ℓ = 2; mℓ = 0
5. n = 3; ℓ = 0; mℓ = 0
6. n = 2; ℓ = 3; mℓ = 0
7. n = 3; ℓ = 1; mℓ = −1
answer
4. n = 3; ℓ = 2; mℓ = 0
3 refers to the principal quantum number n. d corresponds to the subsidiary quantum number ℓ = 2. Since ℓ = 2, mℓ could be −2, −1, 0, 1 or 2.
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Which light packs the highest energy per photon?
1. red
2. ultraviolet
3. green
4. infrared
5. blue
answer
2. ultraviolet
question
Write the ground-state electron configuration of a lead atom.
1. [Xe]4f14 5d10 6s1 6p3
2. [Xe]4f14 5d10 6s2 6p2
3. [Xe]4f14 5d5 6s1 6p6 7s2
4. [Xe]4f14 5d10 6p4
5. [Xe]4f14 5d9 6s2 6p3
answer
2. [Xe]4f14 5d10 6s2 6p2
The Aufbau order of electron filling is 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, etc. s orbitals can hold 2 electrons, p orbitals 6 electrons, and d orbitals 10 electrons. Note some exceptions do occur in the electron configuration of atoms because of the stability of either a full or half-full outermost d-orbital, so you may need to account for this by 'shuffling' an electron from the (n − 1)s orbital. Finally use noble gas shorthand to get the answer: [Xe]4f14 5d10 6s2 6p2.
question
What subshells correspond to the principal quantum number n = 6?
1. 6s, 6p, 6d, 6f, 6g, 6h, 6i
2. 6s, 6p, 6d, 6f
3. 6s, 6p, 6d, 6f, 6g
4. 6s, 6p
5. 6s, 6p, 6d
6. 6s, 6p, 6d, 6f, 6g, 6h
answer
6. 6s, 6p, 6d, 6f, 6g, 6h
For n = 6, ℓ = 0, 1, 2, 3, 4, 5, so there are 6 subshells.
question
How many total orbitals are there in the shell with n = 6?
1. 16
2. 9
3. 49
4. 36
5. None of these
6. 25
answer
4. 36 correct
Explanation: 1 + 3 + 5 + 7 + 9 + 11 = 36 (= 62)
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Wavelength is the
answer
4. distance between successive peaks in a wave.
Explanation: Definition
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The lines in an atomic line emission spectrum are due to
answer
1. the movement of electrons from higher energy states to lower energy states in atoms.
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The number that describes the main energy level of an electron in an atom is
answer
1. the principal quantum number n.
Explanation: The principal quantum number n defines the energy level of each electron in an atom.
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The angular momentum quantum number provides us with information about which characteristic of an electron bound in an atom?
1. electron spin
2. electron mass
3. orbital charge
4. orbital energy
5. orbital shape
Explanation: The angular momentum quantum number, ℓ, determines the shape of the orbital.
answer
5. orbital shape
Explanation: The angular momentum quantum number, ℓ, determines the shape of the orbital.
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In a given atom, what is the maximum number of electrons that can have principal quantum number n = 3?
1. 2
2. 32
3. 18
4. 10
5. 8
answer
3. 18
Explanation: There are 2 electrons in the 3s orbital, 6 electrons in the 3p orbitals, and 10 electrons in the 3d orbitals to give a total of 18 electrons.
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The wavelength of light in the visible range is
answer
. intermediate between the size of a bacterial cell and that of a virus. Explanation: Visible light is about 400-700 nm in wavelength.
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The current theory is that an atom's electrons are
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3 more like waves than particles when localized in an atom.
Explanation: The current atomic theory states that electrons have both particle- and wave-like characteristics.
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How many electrons can possess this set of quantum numbers: principal quantum number n = 4, angular quantum number ℓ = 2?
1. 12
2. 14
3. 6
4. 4
5. 0
6. 8
7. 18
8. 2
9. 10
10. 16
answer
9. 10
Explanation:
Use the rules for the quantum numbers: If n = 4 and ℓ = 2 (i.e., 4d), then mℓ = −2, −1, 0, +1, +2 are permitted; there are five different orbitals and ms = ± 1 2 , each holding two electrons.
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The higher the energy of electromagnetic radiation, the
answer
shorter its wavelength
Explanation: For electromagnetic radiation, the energy of radiation is related to its frequency by the equation E = hν ,
where h is Planck's constant, ν =
c λ
, and c is the speed of light in a vacuum (also a constant). Thus, the equation that relates energy to wavelength for electromagnetic radiation is
E =
hc λ As energy increases, ν (frequency) must also increase, and λ (wavelength) must decrease.
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Frequency is measured in Hertz and has the units
1. meters.
2. meter/sec.
3. Joules · sec.
4. sec−1.
answer
4. sec−1.
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Set(s) of possible values of mℓ are A) −4; −3; −2; −1; 0; +1; +2; +3; +4 B) −3; −2; −1; 0; +1; +2; +3 C) −2; −1; 0; +1; +2 D) −1; 0; +1 E) 0 Select the best choice for n = 3.
1. only C, D, and E
2. only A
3. only C
4. only E
5. A, B, C, D, and E
6. only B, C, D, and E
7. only B
8. only D and E
9. only D
answer
1. only C, D, and E
Explanation: For any value of n, the possible values of ℓ range from 0 up to (n − 1). In turn, for any value of ℓ, the possible values of mℓ range from = −ℓ, ..., 0, ..., +ℓ. Since n = 3, ℓ can be 0, 1, or 2. Therefore when ℓ = 2, C) mℓ = −2; −1; 0; +1; +2 when ℓ = 1, D) mℓ = −1; 0; +1 when ℓ = 0, E) mℓ = 0
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Hund's rule states that
answer
electrons occupy all the orbitals of a given sublevel singly before pairing begins.
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The energy of a photon is inversely proportional to its wavelength.
1. True correct
2. False
Explanation:
E = hc / λ ∝ 1? λ
As wavelength increases, energy decreases
answer
1. True
Explanation:
E = hc / λ ∝ 1/ λ
As wavelength increases, energy decreases
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The energy level model of the atom was proposed by
answer
Bohr.
Explanation: Bohr's model of the atom includes the notion of discrete energy levels.
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What is the correct order of decreasing energy?
1. γ-rays, x-rays, ultraviolet light, visible light, microwaves
2. microwaves, visible light, x-rays, γ-rays, ultraviolet light
3. visible light, ultraviolet light, microwaves, x-rays, γ-rays
4. microwaves, visible light, ultraviolet light, x-rays, γ-rays
5. visible light, microwaves, x-rays, γ-rays,
ultraviolet light
answer
1. γ-rays, x-rays, ultraviolet light, visible light, microwaves
Explanation: γ-rays > x-rays > ultraviolet light > visible light > microwaves
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What distinguishes one element from another?
.
answer
the number of protons
Explanation: Number of protons = atomic number.
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Identify the set(s) of four quantum numbers n ℓ mℓ ms A. 4, 2, −1, + 1 2 B. 2, 2, −1, + 1 2 C. 5, 0, −1, + 1 2 that are FORBIDDEN for an electron in an atom
1. C only
2. A and B only
3. All are invalid.
4. A only
5. A and C only
6. B and C only
7. B only
8. None is invalid.
answer
6. B and C only
Explanation: B) The maximum value ℓ can have is n − 1; since n = 2, ℓmax = 1. C) ℓ = 0, so mℓ must also equal 0
question
According to the Aufbau principle, what orbital is filled after the 6s orbital?
1. 4f
2. 4d
3. 6p
4. 5d
answer
1. 4f
Explanation: According to the Aufbau principle, the lowest energy orbitals fill first. The order is as follows: 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p, etc.
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How many d electrons does an atom of zirconium (Zr, atomic number = 40) have in its n = 4 shell?
1. 4
2. 2
3. 8
4. 0
5. 10
answer
2. 2
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Consider two photons: Photon X with energy 1.0×10−18 J and photon Y with energy 1.0× 10−17 J. Which statement is true?
1. You cannot determine relative wavelengths and frequencies just given these energies.
2. X has the longer wavelength and higher frequency.
3. X has the longer wavelength and lower
frequency.
4. X has the shorter wavelength and higher frequency.
5. X has the shorter wavelength and lower frequency.
answer
3. X has the longer wavelength and lower
frequency.
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For any principal energy level in an atom, there are (1, 3, 6) p orbitals; they may contain a total of (3, 6, 12) electrons.
1. 1; 6
2. 3; 3
3. 6; 6
4. 3; 6
5. 6; 12
answer
4. 3; 6
Explanation: The principle energy level is n, the subshell is ℓ, and the orbital is mℓ. For ℓ = p = 1, mℓ can have values −1, 0, and 1, which is a total of 3 orbitals. Each orbital can hold 2 electrons designated ms = +1 2 or − 1 2 fora total of 6 electrons per subshell.
028 1.0 points A neutral atom has two electrons with n = 1, eight electrons with n = 2, eight electrons with n = 3, and one electron with n = 4. It has no other electrons. What is the atomic number of this element?
Correct answer: 19.
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The photoelectric effect provided strong evidence for
answer
the particle nature of light.
Explanation: When electromagnetic radiation (light) of sufficient minimum energy strikes a metal cathode, electrons are knocked off its surface, travel to an anode, and form a current through a circuit. Two important observations were: 1) Electrons can be ejected only if the light is sufficiently energetic. Electron ejection is independent of time or intensity. The minimum energy varies by element. 2) The current increases with increasing intensity and is independent of color. Therefore, light is made up of photons, each having a particular amount of energy that can be transferred to an electron during a collision. If the energy is equal to or greater than the amount needed to liberate the electron, it can escape to join the photoelectric current. Intensity is the number of photons hitting a surface per unit time.
question
3d ↑↓ 3s ↑↓ 2p ↑↓ 2s ↑↓ 1s ↑↓
Consider the electron filling diagram for a ground state atom above. Assume any unwritten orbitals are empty. Which of the following does it violate? I) The Aufbau principle II) Hund's rule III) The Pauli exclusion principle
1. II only
2. II, III
3. III only
4. I, II, III
5. I only
6. I, II
7. I, III
answer
6. I, II Explanation:
The Aufbau principle dictates that the 3p (empty and absent from the diagram) orbital would fill before the 3d (2 electrons). Hund's rule dictates that the 2 electrons in the 3d orbital should be in separate orbitals with identical spins rather then the same orbital with opposed spins.
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The Bohr theory of the hydrogen atom
answer
accounts for the fact that light of only certain wavelengths is given off when a hydrogen atom is excited.
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The quantum mechanical approach to atomic structure permits the calculation of
answer
a region about the nucleus in which an electron of specified energy will probably be found.
According to the Heisenberg Uncertainty Principle, the momentum and the position of an electron cannot both be known simultaneously with any accuracy. The quantum mechanical approach attempts to calculate the energy of the electron exactly by defining possible energy states for the electron. The position of the electron cannot then be known with any certainty. Instead, a region of space around the nucleus is identified in which the electron is likely to be. These regions of space are commonly known as orbitals.
question
Which of the following emission lines corresponds to part of the Balmer series of lines in the spectrum of a hydrogen atom?
A) n = 2 → n = 1
B) n = 4 → n = 2
C) n = 4 → n = 1
D) n = 3 → n = 2
E) n = 4 → n = 3
1. B, C, and E only
2. B and D only
3. A, D, and E only
4. E only
5. A and C only
6. D and E only
7. B and C only
.
answer
2. B and D only
Explanation: The Balmer series is produced by electronic transitions which either begin (absorption spectra) or end (emission spectra) at the energy level n = 2. These correspond mostly to the visible region.
question
When sodium is heated, a yellow spectral line whose energy is 3.37 × 10−19 J/photon is produced. What is the frequency of this light?
1. 3.37 × 1019 Hz
2. none of above
3. 5.09 × 10−34 Hz
4. 6.626 × 10−34 Hz
5. 5.9 × 10−7 Hz
6. 5.09 × 1014 Hz
7. 3.0 × 108 Hz
8. 1.602 × 10−19 Hz
9. 3.37 × 1011 Hz
Explanation: Ephoton = 3.37 × 10−19 J/photon ν = ?
Ephoton = hν
ν = Ephoton/ h
=
3.37 × 10−19 J / 6.626 × 10−34 J · s
= 5.09 × 1014 Hz
answer
6. 5.09 × 1014 Hz
Explanation:
Ephoton = 3.37 × 10−19 J/photon ν = ?
Ephoton = hν
ν = Ephoton/ h
=
3.37 × 10−19 J / 6.626 × 10−34 J · s
=
5.09 × 1014 Hz
question
What is its wavelength?
1. 6.626 × 10−34 m
2. 5.09 × 1014 m
3. 1.602 × 10−19 m
4. none of above
5. 5.9 × 10−7 m
6. 3.0 × 108 m
answer
5. 5.9 × 10−7 m
Explanation: λ = ?
c = λν
λ =c/ ν
=
3.0 × 108 m/s / 5.09 × 1014 Hz λ
=
5.9 × 10−7 m
question
Which of the following experiments provided evidence that the electrons in atoms are arranged in distinct energy levels?
answer
1. the observation of line spectra from gas discharge tubes
Explanation: The fact that gases emitted only specific wavelengths of energy suggested that electron energy states are quantized.
question
Determine the energy of a photon whose frequency is 2.64 × 1017 Hz.
answer
Correct answer: 1.74926 × 10−16 J.
Explanation:
ν = 2.64 × 1017 Hz Ephoton = ?
Ephoton = hν
=
(6.626 × 10−34 J · s) × (2.64 × 1017 Hz)
= 1.74926 × 10−16 J
question
Frequency is
answer
3. the number of waves passing a fixed point in one second.
question
Calculate the energy of a photon of light with a wavelength of 0.77 km.
1. 2.6 × 10−23 J
2. 390000 J
3. 2.6 × 10−28 J
4. 3.9 × 1011 J
5. 2.6 × 10−22 J
6. 5.1 × 10−34 J
7. 5.1 × 10−31 J
8. 3.9 × 108 J
9. 2.6 × 10−25 J
answer
3. 2.6 × 10−28 J correct
Explanation: λ = 0.77 km
Here we use the equation
E = hc / λ
where h is Planck's constant (6.6262 × 10−34 J·s) and c is the speed of light (3.00 × 108 m/s). Here we'll also need to convert km into meters (recall that 1 km = 1 × 103 m):
E
=
(6.6262 × 10−34J · s)(3.00 × 108 m/s) / 0.77 km (1.00 × 103 m 1 km)
=
2.58164 × 10−28 J
question
A visible light photon has a than a photon of microwave radiation is
answer
higher frequency
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Potassium atoms that are excited with energy give off purple light. When this light is bent by a prism and sent to a detector, we would expect to see
.
answer
mostly black space within lines of color; at least some of them in the purple region.
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Bohr's theory of the hydrogen atom assumed that
answer
the electron can exist in any one of a set of discrete states (energy levels) and can move from one to another by emitting or absorbing radiation.
question
Which characteristic describes a nonmetal?
1. good insulator
2. malleable
3. good conductor
4. lustrous
5. ductile
answer
1. good insulator
Explanation: Non-metals are good insulators (poor conductors), brittle and not shiny. Metals are
matuszewski (vm22554) - Assignment #8: Chapter 6 - Periodicity - reisener - (60011) 2
lustrous, malleable, ductile, and good conductors.
question
If the neutral atom of an element has only 3 valence electrons it must be in which group?
1. IIIA
2. IVA
3. VA
4. VIA
5. IVB
6. VIIA
answer
1. IIIA
Explanation: The number of valence electrons in any atom of a representative element corresponds to its group number. So, if the element has 3 valence electrons, it must be in the group IIIA of the periodic table.
question
From the data below
Element First Ionization Energy
1 1310 kJ/mol
2 1011 kJ/mol
3 418 kJ/mol
4 2080 kJ/mol
5 947 kJ/mol
which element is likely to be a metal?
1. 3
2. 2
3. 4
4. 5
5. 1
answer
1. 3
Explanation: Metals form positive ions; therefore they are likely to have relatively low first ionization energies. (It will be easy to remove the first electron.)
question
For which of these group IA metals is the shielding effect by the core electrons presumably the strongest?
1. Na
2. Fr
3. Rb
4. H
answer
2. Fr
Explanation: Fr has the most electrons and the more electrons you have, the stronger the shielding effect. As we go down the periodic table, atomic radius increases because the shielding effects of inner electrons reduces the effective charge experienced by outer shell electrons
question
Write an equation for the second ionization energy of calcium.
1. Ca+(g) + e− → Ca−(g)
2. Ca(g) → Ca2+(g) + 2e−
3. Ca+(g) + 2e− → Ca2+(g)
4. Ca+(g) → Ca2+(g) + e−
5. Ca+(g) + e− → Ca(g)
answer
4. Ca+(g) → Ca2+(g) + e−
question
The elements in a period
1. belong to the same family.
2. are not alike in properties.
3. are arranged alphabetically.
4. have identical properties.
answer
2. are not alike in properties.
Explanation: Elements in a period tend to have similar size, but different properties.
question
Which of the following atoms has the largest radius?
1. Ar
2. F
3. H
4. Al
5. Na
6. P
Explanation: Atomic radii increase from left to right and from top to bottom on the Periodic Table
answer
5. Na
Explanation: Atomic radii increase from left to right and from top to bottom on the Periodic Table
question
Rank the elements F, O, P and Mg in order of increasing first ionization energies.
1. Mg < P < O < F
2. F < O < P < Mg
3. O < F < P < Mg
4. Mg < P < F < O
5. Mg < O < F < P
answer
1. Mg < P < O < F
Explanation: Ionization energy generally increases from left to right across the Periodic Table.
question
Rank the following in terms of decreasing ionic radii.
1. N3−,O2−,F−,Na+,Mg2+
2. Na+,Mg2+,O2−,N3−,F−
3. F−,O2−,N3−,Na+,Mg2+
4. Na+,Mg2+,N3−,O2−,F−
5. Mg2+,Na+,F−,O2−,N3−
answer
Rank the following in terms of decreasing ionic radii
1. N3−,O2−,F−,Na+,Mg2+
Explanation: We only consider ions that yield a Noble
gas configuration (Na+, Mg2+, O2−, N3−, and F−). We are comparing ions with the same number of electrons: 10 total and 8 valence in this case. The number of protons in the ion is the biggest determinate of the size when electron number is constant. The greater the effective nuclear charge, the stronger the attraction between the protons and the electrons, and thus the smaller the radii
question
According to the general trends of the periodic table, which of the following elements has the largest atomic radius?
1. Ca
2. K
3. Cs
4. Kr
answer
3. Cs
Explanation: Following the general pattern, which is that atomic sizes are largest in the bottom left hand corner and smallest in the top right-hand corner of the periodic table, the largest atomic radius would belong to Cs in this group
question
The alkali metals have a low first and a high second ionization potential. The alkaline earth metals have low values for both first and second potentials. These observations suggest that
1. alkali metals should form stable −1 ions, while alkaline earth metals should form stable −2 ions.
2. both alkali metals and alkali earth metals should form very stable ions with charge −1.
3. both alkali metals and alkaline earth metals should form stable ions with charge +1.
4. alkali metals should form stable +1 ions, while alkaline earth metals should form stable −2 ions.
5. alkali metals should form stable +1 ions, while alkaline earth metals should form stable +2 ions.
answer
5. alkali metals should form stable +1 ions, while alkaline earth metals should form stable +2 ions.
Explanation: In order to attain the electron configuration of the nearest noble gas, alkali metals lose one electron to form monovalent cations and alkaline earth metals lose 2 electrons to form divalent cations. Any additional electron loss will be from filled orbitals and will require much larger energies.
question
Arrange the following atoms in order of increasing radius: Li, Au, C, Cs.
1. Cs < Au < Li < C
2. C < Li < Au < Cs
3. Li < C < Cs < Au
4. Au < Cs < C < Li
answer
2. C < Li < Au < Cs
Explanation: Atomic radius decreases across a period due to increasing effective nuclear charge (ENC) and increases down a group due to decreasing ENC and the increase in total electrons
question
Why is it harder to remove an electron from fluorine than from carbon, or, to put it another way, why are the valence electrons of fluorine more strongly bound than those of carbon?
1. Fluorine has a nearly filled octet, which is always more stable than a partially filled octet.
2. The statement is false; it takes very nearly the same energy to remove an electron from (ionize) both elements.
3. The valence electrons of both fluorine and carbon are found at about the same distance from their respective nuclei but the greater positive charge of the fluorine nucleus attracts its valence electrons more strongly. correct
answer
3. The valence electrons of both fluorine and carbon are found at about the same distance from their respective nuclei but the greater positive charge of the fluorine nucleus attracts its valence electrons more strongly. correct
For each element, the valence electrons are in the 2s and the 2p orbitals:
C : 1s22s22p2;
6 protons in the nucleus;
6 electrons (total);
4 valence electrons.
F : 1s22s22p5;
9 protons in the nucleus;
9 electrons (total);
7 valence electrons.
The effective nuclear charge felt by the valence electrons of fluorine is greater than the effective nuclear charge felt by the valence electrons of carbon. Therefore, the valence electrons of fluorine experience a greater Coulombic attractive force and are harder to remove.
question
Consider the most stable ions which are formed by the elements Cs, Ba, Te and I. Which element will form the ion with the largest radius? (Hint: the ions will be isoelectronic.)
1. Ba
2. I
3. Te
4. Cs
answer
3. Te
Explanation: The ions which form are Ba2+, Cs+, Te2− and I−. Although size decreases from left to right across the periodic table due to increasing effective nuclear charge, the negative ions will be the largest ions, and the negative ion with the largest charge will have the largest radius since the electrons will repel each other and the effective nuclear charge will be insufficient to overcome this repulsion.
question
The ions K+, Ca2+, and Cl− each have eighteen electrons. The order of sizes of these three ions would be
1. Cl− is smaller than Ca2+ which is smaller than K+.
2. Ca2+ is smaller than Cl− which is smaller than K+.
3. Ca2+ is smaller than K+ which is smaller than Cl−.
4. K+ is smaller than Ca2+ which is smaller than Cl−.
5. Cl− is smaller than K+ which is smaller than Ca2+.
answer
3. Ca2+ is smaller than K+ which is smaller than Cl−.
Explanation: These ions are isoelectronic. In an isoelectronic series, ionic size decreases with increasing atomic number due to increased nuclear charge.
question
Fill in the blanks: potassium is one of the most well-known elements in the alkali metal . It is in the which makes it a element. Its single valence electron is in the subshell of the shell, making it very reactive. It reacts readily with non-metals to form .
1. row; d block; main group; ℓ = 1; n = 4; salts
2. family; s block; main group; ℓ = 0; n = 4; salts
3. row; d block; non-metal; ℓ = 1; n = 3; alloys
4. family; s block; reactive; ℓ = 0; n = 3; alloys
5. series; s block; common; ℓ = 2; n = 4; networks
answer
2. family; s block; main group; ℓ = 0; n = 4; salts
Explanation: Family refers to the common name of a group or groups of similar elements, e.g., rare earth, coinage metal, halogen. The number (1-18) of the column of an element is the group. All elements in rows 3-12 are called d-block elements, while the rest of the rows are called main group elements. Potassium is on row 4, but the principal quantum number n always refers to an electron shell. The 4s electron of K is its entire valence. K+ is isoelectronic to group 18 which are called the noble gases. The reaction of a metal and non-metal usually produces a salt.
question
Rank the following atoms in terms of decreasing atomic radius.
1. F, O, N, Mg, Na
2. F, O, N, Na, Mg
3. Na, N, O, Mg, F
4. F, Mg, Na, O, N
5. Na, Mg, N, O, F
answer
5. Na, Mg, N, O, F
Explanation: As you move down the periodic table atomic radius increases because the shielding effects of inner electrons reduces the effective nuclear charge experienced by outer shell electrons. As you move across the periodic table the radius decreases because electrons are being added to the same electronic shell (and thus do not add additional shielding effects) while the number of protons increases. Na, being farthest left and down the table, would be the largest while F, being farthest right and up the table, would be the smallest.
question
Rank the following species from smallest to largest atomic radius: K, Mg, Rb, Ca.
1. Mg < Rb < K < Ca
2. Rb < K < Ca < Mg
3. Mg < K < Ca < Rb
4. Mg < Ca < K < Rb
5. Mg < Ca < Rb < K
answer
4. Mg < Ca < K < Rb
Explanation: Atomic radii increase down and to the left.
question
The Lewis dot structure for an isolated selenium (Se) atom has
1. one pair of electrons and four lone electrons.
2. two pairs of electrons and two lone electrons. correct
3. three pairs of electrons.
4. four lone electrons.
5. four pairs of electrons.
answer
2. two pairs of electrons and two lone electrons.
Explanation:
The electron configuration of Se is
[Ar]4s2 3d10 4p4
By Hund's rule, degenerate orbitals are first filled singly before pairing up electrons with opposite spins. Note that electrons in d orbitals are not shown in Lewis structures.
question
Arsenic (As) is classified as
1. an actinide.
2. a representative element. 3. a transition element.
4. a noble gas.
5. a lanthanide.
answer
2. a representative element.
Explanation: Representative elements are found in the A Groups of the periodic table. As is a Group VA element.
question
What is the proper order of electronegativity?
1. Ca < Be < N < C
2. Ca < Be < C < N
3. Ca > Be > C > N
4. Be < Ca < N < C
5. Ca > Be > N > C
answer
2. Ca < Be < C < N
Explanation: Electronegativity generally increases from left to right and from bottom to top of the Periodic Table.
question
Elements with great electron affinities (large negative values) often have
1. large sizes and high ionization energies.
2. large sizes and low ionization energies.
3. small sizes and high ionization energies.
4. small sizes and low ionization energies.
answer
3. small sizes and high ionization energies.
Explanation: Electron affinities are largest on the right hand side of the periodic table. These elements also have large ionization energies and small radii (relative to other members of the same row on the periodic table).
question
F− is bigger than F because
1. F− has one less electron so there is more effective shielding of the nuclear charge.
2. F− has one less electron so there is less effective shielding of the nuclear charge.
3. F− has one more electron which causes less electron repulsions in the outer orbitals, thus expanding the electron cloud.
4. F− has one more electron which causes greater electron repulsions in the outer orbitals, thus expanding the electron cloud.
5. F− has one more electron so there is less effective shielding of the nuclear charge.
answer
4. F− has one more electron which causes greater electron repulsions in the outer orbitals, thus expanding the electron cloud.
Explanation: Since electrons all have the same charge (negative), their natural tendency is to move as far apart from each other as they can. Since F− has one more electron than F, the protons are less able to draw the electrons towards the nucleus, so the radius expands.
question
Ionization energies decrease going from Li to Na to K. This is because
1. ion electrons are always easy to remove.
2. electrons in outer shells are shielded by electrons in inner shells, thus increasing the effective nuclear charge.
3. the valence shell repulsion theory determines the removal of the electron.
4. The statement is false; ionization energies increase in that order.
5. electrons in the outermost shell are located increasingly farther from the nucleus.
6. lone electrons prefer to be paired up.
answer
5. electrons in the outermost shell are located increasingly farther from the nucleus.
Explanation: In Na the lone valence electron is in the 3s orbital and in K the lone valence electron is farther from the nucleus in the 4s orbital, thus requiring less energy to be removed.
.
question
When atoms lose or gain electrons in chemical reactions they form
1. new atoms.
2. ions.
3. nucleus
4. noble gases.
answer
2. ions.
Explanation: A neutral atom has an equal number of protons and electrons. The gain or loss of electrons forms an ion (a particle with a net negative or positive charge). The atomic number (number of protons) determines what element an atom is. A change in the number of electrons does not change the atomic number and will not change the atom into a different element. While many ions have the same electron configuration as a noble gas, these atoms do not become a noble gas; they still have the same number of protons as the original neutral atom and are therefore still the same element
question
A row on the periodic table is called a , and a column is called a . Lithium and Beryllium are examples of and , respectively.
1. period, series, alkaline earth metal, alkali metal
2. series, family, alkaline earth metal, chalcogens
3. period, group, alkali metal, pnictogens
4. period, group, alkali metal, alkaline earth metal
5. family, group, alkali metal, trials
answer
4. period, group, alkali metal, alkaline earth metal
Explanation: A row on the periodic table is called a period, and a column is called a group or family. Lithium and Beryllium are examples of alkali metal and alkaline earth metal, respectively
question
Consider the compound C6H7O2(OH)3. How many atoms of oxygen are present?
1. 1
2. 6
3. 4
4. 5
5. None of these
6. 3
7. 2
Explanation: O2 contains two oxygens and (OH)3 three more.
answer
4. 5
Explanation: O2 contains two oxygens and (OH)3 three more.
question
How many moles of oxygen atoms are in 6.093 g of calcium hydroxide?
answer
Correct answer: 0.16447 mol.
Explanation:
mCa(OH)2 = 6.093 g
Calcium ions have a charge of +2. Hydroxide ions have a charge of −1. The formula for calcium hydroxide is Ca(OH)2. To solve this problem we need the formula weight of Ca(OH)2:
* dimensional analysis; anything that's after / is on the bottom*
FWCa(OH)2 =
1 mol Ca × 40.078 g Ca / mol Ca
+ 2 mol O × 15.9994 g O / mol O
+ 2 mol H × 1.00794 g H / mol H
=
74.0927 g Ca(OH)2 / mol Ca(OH)2
The formula weight issued to convert grams Ca(OH)2 to moles Ca(OH)2:
? mol Ca(OH)2 = 6.093 g Ca(OH)2
×
mol Ca(OH)2 / 74.0927 g Ca(OH)2
= 0.0822348 mol Ca(OH)2
Each mole of Ca(OH)2 contains 2 mol of O. We can use this ratio to convert from moles Ca(OH)2 to moles O:
? mol O = 0.0822348 mol Ca(OH)2
×
2 mol Ca / 1 mol Ca(OH)2 = 0.16447 mol O
question
How many hydrogen atoms are in 0.102 mol of H2SO4?
answer
Correct answer: 1.22849 × 1023 atoms H.
* dimensional analysis; anything that's after / is on the bottom*
Explanation: n = 0.102 mol Each mole of H2SO4 contains 2 mol of H. We can use this ratio to convert from moles H2SO4 to moles H:
? mol H = 0.102 mol H2SO4 × 2 mol H / 1 mol H2SO4
= 0.204 mol H
Finally, Avogadro's number can be used to convert from moles H to atoms H:
? atoms H = 0.204 mol H × 6.02 × 10^23 atoms H / 1 mol H
= 1.22849 × 1023 atoms H
question
What is the weight of 7.49 × 1021 atoms of phosphorus?
answer
Correct answer: 0.385246 g.
Explanation: n = 7.49 × 1021 atoms
First use Avogadro's number to convert atoms of phosphorus to moles of phosphorus:
? mol P = 7.49 × 1021 atoms P ×1 mol P 6.022 × 10^23 atoms P
= 0.0124377 mol P
Then use the atomic mass of P, 30.974 g/mol, to convert moles to grams:
? g P = 0.0124377 mol P × 30.974 g/mol P
= 0.385246 g P
question
How many moles are in 178.31 g of Fe3(PO4)2?
answer
Correct answer: 0.498713 mol.
Explanation: mFe3(PO4)2 = 178.31 g n = ?
3 mol Fe × 55.85 g Fe / mol Fe = 167.6 g
2 mol P × 30.97 g P/ mol P = 61.94 g
8 mol O × 16.00 g O / mol O = 128.00 g
Molar mass = 357.54 g /mol
nFe3(PO4)2 =
178.31 g / 357.54 g/mol Fe3(PO4)2
= 0.498713 mol
question
A compound formed from titanium and oxygen has the formula TiO2. Which of the following is true about the ratio of number Ti and O atoms?
1. The ratio cannot be determined from the information given.
2. The ratio can vary so long as no element other than Ti and O are present.
3. The ratio is always
1atomTi / 2atomsO
4. The ratio is always
1atomTi / 1atomO
5. The ratio is always
2atomsTi / 1atomO
answer
3. The ratio is always
1atomTi / 2atomsO
Explanation: Subscripts indicate the number of atoms of the element immediately preceding the subscript. In this case, there is no subscript for Ti. This indicates that there is one atom Ti per molecule. The subscript 2 on oxygen indicates there are 2 atoms O per molecule. The
ratio for the compound TiO2 will always be one atom Ti to 2 atoms O.
question
Which family gains electrons most easily?
1. noble gases
2. transition metals
3. alkali metals
4. oxygen group
5. alkaline earth metals
6. halogens
7. rare earth metals
answer
6. halogens
question
What is the mass of 1.500 mol Ca(OH)2?
answer
Correct answer: 111.15 g.
Explanation:
nCa(OH)2 = 1.500 mol m = ?
1 mol Ca × 40.08 g Ca / mol Ca
= 40.08 g
2 mol O × 16.00 g O / mol O
= 32.00 g
2 mol H × 1.01 g H / mol H
= 2.02 g
Molar mass = 74.10 g/mol
mCa(OH)2 =
74.10 g Ca(OH)2 / 1 mol Ca(OH)2
× 1.500 mol
= 111.15 g Ca(OH)2
question
The best Lewis dot structure for Se should have
1. three pairs of dots and one lone dot.
2. two pairs of dots.
3. one pair of dots and three lone dots.
4. three pairs of dots
.
5. two pairs of dots and two lone dots.
answer
.
5. two pairs of dots and two lone dots.
Explanation: Se appears in Group VI on the periodic table, so it has 6 valence electrons, and its Lewis structure contains two pairs of dots and two lone dots.
question
part one ; The approximate population of Earth is 6 billion people. How many moles of people inhabit Earth?
1. 1.541 × 10−14 mol
2. 2.554 × 10−15 mol
3. 7.083 × 10−15 mol
4. 5.32 × 10−15 mol
5. 9.96347 × 10−15 mol
6. 2.033 × 10−14 mol
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
part two; If all people were pea pickers, then how long would it take for the entire population of Earth to pick 1 mol of peas at the rate of one pea per second, working 22 hours per day, 365 days per year?
answer
part one; *DA*
5. 9.96347 × 10−15 mol
Explanation:
? mol x =
6 × 109 people / 6.022 × 1023 people/mol
= 9.96347 × 10−15 mol
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
part two ; * DA: / used when # are divided*
Correct answer: 3.47193 × 106 yrs.
Explanation: In 1 second 6 × 109 peas will be picked,
so (6.022 × 1023 peas) (mult.) 1 s / 6 × 109 peas (mult) 1 hr / 3600 s (mult. ) 1 day / 22 hr (mult.)
1 yr / 365 days
