Chem Ch. 3: Atoms - the Building Blocks of Matter

Neutral atoms contain equal numbers of

• Electrons and neutrons.

• Protons and neutrons.

• Protons and electrons.

• Protons, electrons, and neutrons.

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The following atomic symbol for beryllium indicates what? $_4^9Be$  

• Atomic number is 4.

• Atomic number is 9.

• Mass number is 4.

• Atomic number is equal to 9 - 4.

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The atomic mass of an atom of carbon is 12 amu, and the atomic mass of an atom of oxygen is 16 amu. To produce CO, 16 g of oxygen combine with 12 g of carbon. To produce CO₂, 32 g of oxygen combine with 12g of carbon. The ratio of the mass of oxygen in CO₂ to the mass of oxygen in CO is

• 1:1

• 2:1

• 1:2

• 8:3

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Rutherford’s gold-foil experiment led him to conclude that

• Thomson’s plum pudding model of the atom was accurate.

• Alpha particles were a poor choice for a bombardment material.

• A dense region of positive charge existed somewhere in the atom.

• Light was emitted by electrons returning to ground state.

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Which of the following is not one of the five principles of Dalton’s theory?

• Atoms of different elements combine in simple, whole-number ratios to form compounds.

• All matter is made of indivisible, indestructible atoms.

• All atoms have similar physical and chemical properties.

• Chemical reactions consist of the combination, separation, or rearrangement of atoms.

According to the law of definite proportions, any two samples of KCl will have

• The same mass.

• Slightly different molecular structures but the same two elements.

• Different densities.

• The same elements in the same proportions by mass.

According to the law of conservation of mass, when sodium, hydrogen, and oxygen react to form a compound, the mass of the compound will be

• Equal to the sum of the masses of the reactants.

• Greater than the sum of the masses of the reactants.

• Less than the sum of the masses of the reactants.

• Either less than or equal to the sum of the masses of the reactants.

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An atom of potassium has 19 protons and 20 neutrons. Its mass number is

• 9

• 19

• 20

• 39

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Which of the following is not equal to 1.00 mol of carbon-12?

•  $6.022\times10^{23}$ carbon atoms

• 12.0 g of carbon

• 6.0 g of carbon

•  $6.022\times10^{23}$  & 6.0 g of carbon

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The molar mass of an element is numerically equal to

• The element’s average atomic mass.

• The element’s average atomic number.

• The number of electrons possessed by an element.

• The percentage composition of the element by mass.