Q: Which of the following best explains why the atomic radius decreases as you move from left to right across a period in the periodic table?

The effective nuclear charge ($$Z_{\text{eff}}) $$increases, pulling electrons closer to the nucleus.

Question 1

Which of the following best explains why the atomic radius decreases as you move from left to right across a period in the periodic table?

Accepted Answer

The effective nuclear charge ($$Z_{	ext{eff}}) $$increases, pulling electrons closer to the nucleus.

Question 2

Which of the following elements would have the highest first ionization energy?

Accepted Answer

Argon ($$\mathrm{Ar})$$

Question 3

A neutral atom of sulfur ($$\mathrm{S}) $$gains two electrons to form $$\mathrm{S}^{2-}. $$Compared to the neutral atom, the $$\mathrm{S}^{2-}$$ ion will:

Accepted Answer

Be larger due to increased electron-electron repulsion.

Question 4

Which of the following best describes the trend in ionization energy as you move down a group in the periodic table?

Accepted Answer

Ionization energy decreases due to increased shielding and greater atomic radius.

Question 5

Which of the following statements about the formation of ions is correct?

Accepted Answer

Metals tend to lose electrons to form cations, and nonmetals tend to gain electrons to form anions.

Question 6

Which of the following molecules contains a polar covalent bond?

Accepted Answer

$$\mathrm{H}_2\mathrm{O}$$

Question 7

What is the effective nuclear charge ($$Z_{	ext{eff}}) $$experienced by a 3p electron in a phosphorus atom ($$Z=15$$), given that the shielding constant ($$S) is $$approximately 10?

Accepted Answer

$$Z_{	ext{eff}} = 5$$

Question 8

Which of the following best explains why the second ionization energy ($$E_{i2}) of $$sodium ($$\mathrm{Na}) is $$much higher than its first ionization energy ($$E_{i1}$$)?

Accepted Answer

The second electron is removed from a stable noble gas configuration.

Question 9

Which of the following is the correct Lewis symbol for the chloride ion ($$\mathrm{Cl}^-$$)?

Accepted Answer

Cl with 8 dots and a negative sign

Question 10

Which of the following bonds has the highest bond energy, based on average bond dissociation energies?

Accepted Answer

$$\mathrm{C}\equiv\mathrm{C}$$

Question 11

A molecule of ozone ($$\mathrm{O}_3) $$can be represented by two resonance structures. What is the bond order between the oxygen atoms in ozone?

Accepted Answer

1.5

Question 12

Which of the following statements about electronegativity is correct?

Accepted Answer

Fluorine is the most electronegative element.

Question 13

Which of the following best describes the octet rule?

Accepted Answer

Atoms tend to gain, lose, or share electrons to achieve eight electrons in their outer shell.

Question 14

Which of the following is a correct statement about ionic bonds?

Accepted Answer

Ionic bonds result from the transfer of electrons from one atom to another.

Question 15

Which of the following molecules violates the octet rule?

Accepted Answer

$$\mathrm{BF}_3$$

Question 16

Which of the following best explains why the bond length in a nitrogen molecule ($$\mathrm{N}_2) is $$shorter than in an oxygen molecule ($$\mathrm{O}_2$$)?

Accepted Answer

$$\mathrm{N}_2$$ has a triple bond while $$\mathrm{O}_2$$ has a double bond.

Question 17

Which of the following best describes the relationship between bond order, bond length, and bond strength?

Accepted Answer

As bond order increases, bond length decreases and bond strength increases.

Question 18

Which of the following is the correct electron configuration for the $$\mathrm{O}^{2-}$$ ion?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$

Question 19

Which of the following best describes a nonpolar covalent bond?

Accepted Answer

A bond where electrons are shared equally between two atoms.

Question 20

Which of the following best explains why resonance structures are used to represent some molecules?

Accepted Answer

Because the actual electron distribution is an average of multiple valid Lewis structures.

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