Question 1

Which statement best explains why the number of protons in an atom defines the element?

Accepted Answer

The number of protons (atomic number) is unique for each element and determines its identity.

Question 2

Which law states that in a chemical reaction, matter is neither created nor destroyed?

Accepted Answer

Law of Conservation of Mass

Question 3

A neutral atom of sodium (Na) has an atomic number of 11. How many electrons does it have?

Accepted Answer

$$11$$

Question 4

Which of the following elements is a metalloid?

Accepted Answer

Silicon (Si)

Question 5

Which pair of elements is expected to have the most similar chemical properties?

Accepted Answer

Br and I

Question 6

What is the charge on the ion formed by magnesium (Mg)?

Accepted Answer

$$+2$$

Question 7

Which of the following is a transition element?

Accepted Answer

Mn

Question 8

A neutral atom of chlorine has 17 protons and 18 neutrons. What is its mass number?

Accepted Answer

$$35$$

Question 9

Which element is classified as an alkali metal?

Accepted Answer

Lithium

Question 10

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes have the same number of protons but different numbers of neutrons.

Question 11

A sample of gallium contains two isotopes: $$^{69}\mathrm{Ga} (60.11$$% abundance, mass = 68.9256 amu) and $$^{71}\mathrm{Ga} (39.89$$% abundance, mass = 70.9247 amu). What is the atomic mass of gallium? (Use the formula $$	ext{Atomic mass} = \sum (	ext{fraction of isotope} 	imes 	ext{mass of isotope}))$$

Accepted Answer

$$69.72$$ amu

Question 12

Which of the following ions is isoelectronic with argon ($$\mathrm{Ar}$$)?

Accepted Answer

$$\mathrm{Cl}^-$$

Question 13

Which property is NOT characteristic of metals?

Accepted Answer

Gain electrons to form anions

Question 14

Which group on the periodic table contains the noble gases?

Accepted Answer

Group 8A

Question 15

A neutral atom of phosphorus ($$Z=15) $$gains three electrons. What is the symbol and charge of the resulting ion?

Accepted Answer

$$\mathrm{P}^{3-}$$

Question 16

Which of the following best describes the Law of Multiple Proportions?

Accepted Answer

When two elements form more than one compound, the masses of one element that combine with a fixed mass of the other are in ratios of small whole numbers.

Question 17

Which element is a main-group nonmetal?

Accepted Answer

Sulfur (S)

Question 18

Which of the following elements is most likely to form a $$2+$$ ion?

Accepted Answer

Calcium (Ca)

Question 19

A sample of bromine contains two isotopes: $$^{79}\mathrm{Br}$$ and $$^{81}\mathrm{Br}. If $$the atomic mass of bromine is $$79.904$$ amu and the abundance of $$^{81}\mathrm{Br} is$$ $$49.31\%$$, what is the abundance of $$^{79}\mathrm{Br}$$?

Accepted Answer

$$50.69\%$$

Question 20

Which of the following best describes a cation?

Accepted Answer

An atom that has lost electrons

Atomic Theory, Subatomic Particles, and the Periodic Table

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