3 PRACTICE Test: Atomic Structure and Counting Atoms

According to the law of conservation of mass, when magnesium, sulfur, and oxygen react to form a compound, the mass of the compound is:

• less than the sum of the masses of the individual elements

• equal to the sum of the masses of the individual elements

• greater than the sum of the masses of the individual elements

• either greater than or less than the sum of the masses of the individual elements

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Which of the following is NOT one of Dalton’s 5 postulates on atomic theory?

• Atoms of different elements combine in simple whole-number ratios

• Atoms of the same element are identical and different elements are different

• Atoms cannot be divided, created, or destroyed

• Atoms are composed of small indivisible particles called neutrons

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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):

• Neutron

• Nuclide

• Electron

• Isotope

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The smallest unit of matter that has properties of an element is the:

• Electron

• Atom

• Neutron

• Proton

Isotopes are atoms of the same element that have different:

• Numbers of neutrons

• Numbers of protons

• Numbers of electrons

• Numbers of Chemical properties

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The atomic number of an element is equal to:

• The number of protons

• The number of neutrons

• The mass of an oxygen atom

• The number of protons and neutrons

Chlorine-37 has a nuclear symbol shown in this image. This means it has:

• 17 protons, 37 neutrons, 17 electrons

• 17 protons, 20 neutrons, 17 electrons

• 37 protons, 17 neutrons, 20 electrons

• 20 protons, 17 neutrons, 20 electrons

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Avogadro’s number is:

• The maximum number of electrons an energy level can accommodate

• The number of protons and neutrons in the nucleus of an atom

• the number of particles in 1 gram of a substance

• the number of particles in 1 mole of a pure substance

The molar mass of an element is numerically equal to:

• The number of particles in a sample of that element

• The element’s atomic number

• The number of electrons in that element

• The element’s average atomic mass

Which famous experiment led to the discovery of the electron?

• Cathode ray experiment

• Gold foil experiment

• Oil drop experiment

• Rutherford experiment