Chemistry Unit 3: Study Guide Answers – Flashcards
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What did Democritus propose?
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proposed the idea of atoms
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What did Democritus say about atoms?
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believed that atoms were indestructible and indivisible
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Whose work did Dalton expand on?
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Democritus'
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What were Dalton's theories about atoms?
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1. atoms are indivisible (false) 2. all atoms of an element are identical (false) 3. atoms cannot be destroyed or turned into other atoms (false)
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Which of Dalton's theories stayed true?
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1. Law of Definite Proportions: regardless of the amount, a compound is always composed of the same elements in the same proportion by mass 2. Law of Multiple Proportions: different combinations of 2 or more atoms can exist
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What does the Scanning Tunneling Microscope do?
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allows individual atoms to be observable
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What was J.J. Thomson's contribution to the atomic theory?
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he discovered electrons
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What device did Thomson build and discover?
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the cathode ray
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What are subatomic particles?
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the fundamental parts of an atom (electron, neutron, proton)
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What are the properties of each subatomic particles?
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electrons-negative charge, 0 amu, size 1/1840 neutrons-no charge, 1 amu, size 1 protons-positive charge, 1 amu, size 1
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What was the experiment that contributed to Rutherford's atomic model?
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the Gold-Foil Experiment
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What was Rutherford able to conclude from the results of his experiment?
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1. the atom is mostly empty space 2. all the positive and almost of the mass in the the nucleus
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What is in the nuclear atom?
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it is what the Rutherford atomic model is known as. the protons and neutrons are located in the nucleus the electrons are around the nucleus and occupy almost all of the volume
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What is an atomic number?
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the number of protons in the nucleus of an atom of that element
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How are elements different from each other?
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they are different because they contain different numbers of protons
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What is mass number? And where is most of the mass concentrated at in an atom?
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the total number of protons and neutrons in an atom most of the mass is in the nucleus
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How do you find the number of neutrons?
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# of neutrons = mass number - atomic number
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How do you find the number of electrons in a neutral atom?
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the # of electrons = the # of protons
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What are isotopes?
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isotopes are atoms that have the same # of protons but different # of neutrons
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If you have different numbers of isotopes for an element, what is also different?
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the mass numbers
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What is atomic mass unit? (amu)
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a unit of measurement of the mass of an atom
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What is atomic mass?
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a weighted average mass of the atoms in a naturally occurring sample of the element
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How do you calculate atomic mass of an element?
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you multiply the mass of each isotope by its natural abundance, expressed as a decimal, and then add the products
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What does the table allow you to do?
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it allows you to compare the properties of elements
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What is the horizontal row of the table called?
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a period
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What is the vertical column of the table called?
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a group
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What did Bohr propose?
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1. electrons are found in orbits around the nucleus 2. electrons fill up "orbits" in a specific order 3. lowest energy orbits are closest to the nucleus 4. orbits can only hold specific #'s of electrons
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What does an electron have in Bohr's model of an atom when it is in an orbit?
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energy?
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What is a quantum of energy?
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the amount of energy required to move an electron from one energy level to another
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What does the quantum mechanical model determine?
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-the allowed energies one electron can have -the likelihood of finding the e- in locations around the nucleus
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What is an atomic orbital?
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the region where there is a high probability of finding an electron
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What is principal quantum numbers/principal energy level and what do those indicate?
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principal energy levels indicate the different energy levels of electrons
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What can you find in each principal energy level?
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there may be several orbitals with different shapes at different energy levels
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What do energy sublevels correspond?
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an orbital of a different shape, which describes where the electron is likely to be found
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What are the letters used to indicate atomic orbitals?
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d, s, p, f
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What are the relative shapes of each orbital?
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s orbitals are spherical, p orbitals are dumb-belled shaped, d orbitals are clover-shaped
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How many sublevels are in each principal energy level?
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n=1: one sublevel 1s, n=2: 2 sublevels 2s 2p, n=3: 3 sublevels 3s 3p 3d, n=4: 4 sublevels 4s 4p 4d 4f
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What is electron configuration?
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the ways in which electrons are arranged in various orbitals around the nuclei if atoms
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What are the 3 rules used to find the electron configuration of atoms?
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the Aufbau principle, the Pauli exclusion principle, and Hund's rule
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What is the Aufbau Principle and what does it tell us?
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it tells that electrons occupy the orbitals of lowest energy first
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What is the Pauli Exclusion Principle and what does it tell us?
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1. each orbital can have 2e- occupying 2. in order to have 2 e- occupying the same orbital, the 2e- must have opposite spins
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What is Hund's Rule and what does it tell us?
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all orbitals of the same energy level will get one electron before any orbitals get two
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What is the electron configuration for Be?
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1s²2s²
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What is the electron configuration for N?
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1s²2s²2p³
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What is the electron configuration for Mg?
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1s²2s²2p⁶3s²
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What is the electron configuration for Cl?
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1s²2s²2p⁶3s²3p⁵
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What is the electron configuration for K?
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1s²2s²2p⁶3s²3p⁶4s¹
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How are the elements sorted?
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by their properties
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What did Dmitri Mendeleev propose on the periodic table? How did he have the elements organized?
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a periodic table that could be used to predict properties of undiscovered elements -the elements are arranged by increasing atomic mass
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How is the modern periodic table organized?
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in order of increasing atomic number
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What is the periodic law?
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when elements are arranged in order of increasing atomic # there is a periodic repetition of their physical & chemical properties
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What are the 3 broad classes that elements are grouped into?
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metals, nonmetals & metalloids
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What are some properties of metals?
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good conductors of heat & electric current, all metals are solid at room temp. + metals are ductile, most are malleable
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What are some properties of nonmetals?
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poor conductors of heat & electric currents, most are gases at room temp. S & P are solids Br is liquid, solid nonmetals tend to be brittle
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What are some properties of metalloids?
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have properties similar to metals & non, can behave like both
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What information do the squares in the periodic table display?
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atomic number, electrons in each energy level, element symbol, element name, average atomic mass
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What is the name for Group 1 (1A) elements?
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alkali metals
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What is the name for Group 2 (2A) elements?
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alkaline earth metals
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What is the name for Group 17 (7A) elements?
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halogens
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What is the name for Group 18 (8A) elements?
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noble gases
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How are elements sorted based on their electron configuration?
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elements can be sorted into noble gases, representative elements, transition metals, or inner transition metals
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What is the electron configuration for noble gases (i.e. Ne, Ar, Kr)? What is the trend that you see?
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Ne: 1s²2s²2p⁶, Ar: 1s²2s²2p⁶3s²3p⁶, Kr: 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶
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Which groups on the periodic table are considered representative elements?
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groups 1A through 7A
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What are some example elements that are considered representative elements?
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Boron, Carbon, Nitrogen, Arsenic, Lead, Sodium, Lithium, Potassium, Tin
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What are a few electron configurations for the representative elements?
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Lithium: 1s²2s¹, Arsenic: 1s²2s²2p⁶3s²3p⁶4s²4p³
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Where do you find the transition elements on the periodic table?
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group B, d block and f block
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What are the 2 types of transition elements?
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transition metals and inner transition metals
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Which orbital is present in transition metals?
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d orbitals
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Which orbital is present in inner transition metals?
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f orbitals
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What is the atomic radius?
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measured from the center of the atom to the edge from left to right
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What are the trends for atomic size within groups and across periods in the periodic table? Examples?
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increases from top to bottom, decreases from left to right
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What are ions?
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an atoms that has a + or - charge
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How do ions form?
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when electrons are transferred between atoms
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What is a positive ion called?
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cation
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How does a positive ion form?
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when an atom loses an electron
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What is a negative ion called?
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anion
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How does a negative ion form?
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when an atom gains an electron
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What is ionization energy?
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the energy required to remove an electron from an atom
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What are the trends for first ionization energy within groups and across periods in the periodic table? Examples?
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decreases from top to bottom, increases from left to right
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What are the trends for ionic size within groups and across periods in the periodic table? Examples?
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atomic size decreases from left to right, increases from top to bottom
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What is electronegativity?
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the ability of an atom of an element to attract electrons when the atom is in a compound
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What are the trends in electronegativity within groups and across periods in the periodic table?
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decreases from top to bottom, increases from left to right
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Which element has the lowest electronegativity value?
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Cesium 0.7
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Which element has the highest electronegativity value?
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Fluorine 4.0
