Q: Which of the following best explains why 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 valence electrons closer to the nucleus.

Q: Given the following ions: $$\text{Na}^+$$, $$\text{Mg}^{2+}$$, $$\text{Al}^{3+}$$, and $$\text{O}^{2-}$$, which has the smallest ionic radius and why?

$$\text{Al}^{3+}$$, because it has the highest nuclear charge for the same number of electrons.

Q: Which of the following statements about effective nuclear charge ($$Z_{\text{eff}}) is $$correct?

$$Z_{\text{eff}}$$ increases across a period due to increasing proton number and similar shielding.

Question 1

Which of the following best explains why 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 valence electrons closer to the nucleus.

Question 2

Given the following ions: $$	ext{Na}^+$$, $$	ext{Mg}^{2+}$$, $$	ext{Al}^{3+}$$, and $$	ext{O}^{2-}$$, which has the smallest ionic radius and why?

Accepted Answer

$$	ext{Al}^{3+}$$, because it has the highest nuclear charge for the same number of electrons.

Question 3

Which of the following statements about ionization energy is correct?

Accepted Answer

Ionization energy increases across a period due to increasing $$Z_{	ext{eff}}.$$

Question 4

Which element would you expect to have the most exothermic (most negative) electron affinity?

Accepted Answer

Fluorine ($$	ext{F})$$

Question 5

A student is asked to draw the Lewis structure for the nitrate ion ($$	ext{NO}_3^-). $$Which of the following is true about its resonance structures?

Accepted Answer

All resonance structures have the same arrangement of atoms but differ in the placement of electrons.

Question 6

Which of the following pairs of elements is most likely to form an ionic bond?

Accepted Answer

Sodium and Chlorine

Question 7

Given the following data, which compound has the highest lattice energy? (Assume all ions are singly charged except where noted.)

Accepted Answer

MgO

Question 8

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

Accepted Answer

Metallic character increases because valence electrons are farther from the nucleus and more easily lost.

Question 9

Which of the following molecules is expected to have a polar covalent bond?

Accepted Answer

$$	ext{HCl}$$

Question 10

A student calculates the formal charge on the central atom in $$	ext{CO}_2 as $$follows: $$	ext{FC} = (4) - (4) - (4) = -4. $$What is the error in this calculation?

Accepted Answer

The student incorrectly counted the number of lone pair electrons on carbon.

Question 11

Which of the following best explains why lattice energy increases as the ionic radii decrease?

Accepted Answer

Smaller ions can pack closer together, increasing the electrostatic attraction according to $$E = k \frac{Q_1$ Q_2$}{d}.$$

Question 12

Which of the following statements about effective nuclear charge ($$Z_{	ext{eff}}) is $$correct?

Accepted Answer

$$Z_{	ext{eff}}$$ increases across a period due to increasing proton number and similar shielding.

Question 13

Which of the following best describes the dipole in a molecule of hydrogen fluoride ($$	ext{HF}$$)?

Accepted Answer

The dipole arrow points from hydrogen to fluorine because fluorine is more electronegative.

Question 14

Which of the following is the correct order of increasing metallic character for the elements Ca, Ba, and Mg?

Accepted Answer

Mg \u003c Ca \u003c Ba

Question 15

A patient is exposed to a toxic gas that reacts with water in the lungs to form an acidic solution. Which property of the gas's constituent element would most likely contribute to this behavior?

Accepted Answer

High electronegativity

Question 16

Which of the following best explains why sodium ($$	ext{Na}) is $$more metallic than magnesium ($$	ext{Mg}$$)?

Accepted Answer

Sodium has a lower ionization energy, making it easier to lose electrons.

Question 17

Which of the following statements about resonance structures is correct?

Accepted Answer

The most stable resonance structure minimizes formal charges and places negative charges on the most electronegative atoms.

Question 18

Which of the following bonds is the most polar?

Accepted Answer

$$	ext{H-F}$$

Question 19

A chemist is comparing the lattice energies of $$	ext{NaF}$$ and $$	ext{MgO}. $$Which factor is most responsible for the difference in their lattice energies?

Accepted Answer

The higher charges on Mg$$^{2+}$$ and O$$^{2-} in$$ $$	ext{MgO}.$$

Question 20

Which of the following correctly describes the trend in electron affinity across a period?

Accepted Answer

Electron affinity becomes more negative (more exothermic) across a period.

Periodic Properties and Chemical Bonding: Study Notes and Practice

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