question

the law of conservation of mass follows from the concept that

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atoms are indivisible

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the composition of the two oxides of lead pbO AND PbO2 are explained by the

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law of multiple proportions

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who first proposed an atomic theory based on scientific knowledge

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john dalton

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according to dalton's atomic theory atom

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of each element are identical in size, mass, and other porpotions

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which of the following was not part of daltons atomic theory

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the number of protons in an atom is its atomic number.

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6. The law of definite proportions

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was explained by Dalton's atomic theory.

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In a cathode tube, electrical current passes from one electrode, the _____, to the oppositely charged electrode.

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cathode

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8. Experiments with cathode rays led to the discovery of the

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electron

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Who explained the behavior of positively charged particles being deflected from a metal foil as the nucleus

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Ernest Rutherford

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In the gold foil experiment, most of the particles fired at the foil

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passed through the foil

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The gold foil experiment led to the discovery of the

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nucleus

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What did Rutherford conclude about the structure of the atom?

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An atom contains a small, dense, positively charged central region.

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A nuclear particle that has about the same mass as a proton, but with no electrical charge, is called a(n)

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neutron

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Which part of an atom has a mass approximately equal to 1 2000 of the mass of a common hydrogen atom

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electron

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the mass of the neutron

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about the same as that of a proton

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The nucleus of most atoms is composed of

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tightly packed protons and neutrons

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17. Protons and neutrons strongly attract when they

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are very close together

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18. An aluminum isotope consists of 13 protons, 13 electrons, and 14 neutrons. Its mass number is

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27.

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19. Isotopes are atoms of the same element that have different

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masses

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20. Atoms of the same element that have different masses are called

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isotopes

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21. Isotopes of an element contain different numbers of

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nuetrons

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. When the light from excited atoms of an element is passed through a prism, the distinct colored lines produced are called

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line - emmision spectrume

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Bohr's theory helped explain why

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excited hydrogen gas gives off certain colors of light.

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24. According to Bohr's theory, an excited atom would

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radiate energy

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25. If electrons in an atom have the lowest possible energies, the electrons are in their

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ground states

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26. For an electron in an atom to change from the ground state to an excited state,

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energy must be absorbed

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27. Most of the volume of an atom is occupied by the

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electron cloud

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28. The main energy levels of an atom are indicated by the

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principal quantum numbers

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29. The letter designations for the first four sublevels, with the number of electrons that can be accommodated in each sublevel are

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s: 2, p: 6, d: 10, and f: 14.

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30. The number of orbitals for the d sublevel is

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5

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31. The statement that an electron occupies the lowest available energy orbital is

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hund's rule

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"Orbitals of equal energy are each occupied by one electron before any is occupied by a second electron, and all electrons in singly occupied orbitals must have the same spin" is a statement of

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hunds rule

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33. The statement that no more than two electrons in the same atom can occupy a single orbital is

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a. the Pauli exclusion principle.

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34. Which of the following rules requires that each of the p orbitals at a particular energy level receive one

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Hund's rule

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35. Two electrons in the 1s orbital must have different spin quantum numbers to satisfy

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the Pauli exclusion principle.

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36. The sequence in which energy sublevels are filled is specified by

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aufbau principal

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38. The carbon-12 atom is assigned a relative mass of exactly

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12 amu

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The abbreviation for atomic mass unit is

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1amu

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The statement that a chemical compound always contains the same elements in exactly the same proportions is called the law of

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definite porportions

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The statement that mass cannot be created or destroyed in ordinary chemical and physical changes is called the law of

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conservation of mass

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The statement that when two elements combine to form two or more compounds, the mass of one element that combines with a given mass of the other element is in the ratio of small whole numbers is known as the law of

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multiple porportions

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A subatomic particle that has a negative electric change is a(n)

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electron

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5. An atom's central region, which is made up of protons and neutrons, is the

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nucleus

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A subatomic particle that has a positive charge and that is found in the nucleus of an atom is a(n)

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proton

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7. A subatomic particle that has no charge and is found in the nucleus is a(n)

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neutron

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8. The number of protons in the nucleus of an atom is called the

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atomic number

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9. The sum of the numbers of protons and neutrons of the nucleus of an atom is called the

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mass number

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An atom that has the same number of protons as other atoms of the same element but has a different number of neutrons is called a(n)

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isotope

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Another method of writing the nickel isotope, 28 58Ni, is

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nickel- 58

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A region in an atom where there is a high probability of finding electrons is called a(n)

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orbital

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Orbitals are sometimes called electron ____________________ because they do not have hard boundaries.

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clouds

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All of the frequencies or wavelengths of electromagnetic radiation make up the electromagnetic

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spectrum

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The wavelength of electromagnetic radiation is inversely proportional to its

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frequency

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Light can be thought of as a stream of particles, the _________________ of which is determined by the lights frequency

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energy

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17. A state in which an atom has more energy than it does in its ground state is called a(n)

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excited states

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A number that specifies a property of an orbital is called a(n)

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quantum number

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The statement that two particles of a certain class cannot be in the exact same energy state is known as the ____________________ principle.

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pauli exclusion

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The _________________________ of an atom is the arrangement of its electrons.

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electron configuration

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The statement that the structure of each successive element is obtained by adding one proton to the nucleus of the atom and one electron to the lowest-energy orbital that is available is known as the ____________________ principle.

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aufbau

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The statement that for an atom in the ground state, the number of unpaired electrons is the maximum possible and these unpaired electrons have the same spin is known as ____________________ rule.

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hunds

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The mass of an atom expressed in atomic mass units is the

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atomic number

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The SI base unit used to measure the amount of a substance whose number of particles is the same as the number of particles in 12 g of carbon-12 is called the

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mole

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Avogadro's number has a value (to three significant figures) of

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6.02 x10^23

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The mass in grams of 1 mol of a substance is the substance's

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molar mass

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. What is the atomic number of the atom 31 P?

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15

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How many electrons are in a neutral atom of 130Ba

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56

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How many protons are in an atom of 91 Zr

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40

question

How many neutrons are in an atom of 144 Sm?

answer

82

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What is the molar mass of tin, which has an atomic mass of 118.7 amu?

answer

118.7g/mol

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What is the mass of 2.5 moles of carbon?

answer

2.5molesC×12.01g/1molcC =3.0×101 gC

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How many moles of copper are present in 180.0 g Cu?

answer

180.0 g Cu × 1molCu /63.546 Cu= 2.833 moles Cu

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3. The mass of 1 mol of gold atoms is 196.97 g. Find the mass of 1 atom of gold.

answer

196.97 Au/1mol× 1mol Au/6.022 ×10^23 = 3.27 × 10−22 g / atomAu

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4. How many atoms are in 0.12 mol of cadmium?

answer

0.12molCd×6.022 ×10^23 atoms Cd/1 mol Cd atoms =7.3×1022 atomsCd

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Describe atomic mass.

answer

Atomic mass is the sum of the masses of the total number of protons and neutrons in the atom.

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Describe the atomic mass unit.

answer

The atomic mass unit is the average of the mass of the protons and neutrons in the carbon-12 isotope.

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3. How are the atomic mass unit and the atomic mass related?

answer

The atomic mass is the atomic mass unit multiplied by the number of protons and neutrons in the atom.

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4. How did chemist come up with the numbers for atomic mass used on the periodic table?

answer

they took all the natural isotopes masses and divided it to find an average

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Who is Robert Millikan and what discovery did he make towards the modern understanding of the atom?

answer

he discovered the charges in an element

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