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

Accepted Answer

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

Question 2

Given the following first ionization energies (IE$$_1) in kJ/$$mol: Na (496), Mg (738), Al (578), Si (786), which element would you expect to have the highest metallic character?

Accepted Answer

Na

Question 3

Which of the following equations correctly represents the process of the first ionization energy for magnesium?

Accepted Answer

$$\mathrm{Mg}(g) \rightarrow \mathrm{Mg}^+(g) + e^-$$

Question 4

Why is the second ionization energy of sodium much higher than its first ionization energy?

Accepted Answer

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

Question 5

Which of the following elements has the most negative electron affinity, and what does this imply about its tendency to gain electrons?

Accepted Answer

Chlorine; it has a strong tendency to gain electrons.

Question 6

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 atomic radius and electron shielding.

Question 7

Consider the reaction: $$\mathrm{Cl}_2(g) + 2 \mathrm{I}^-(aq) \rightarrow 2 \mathrm{Cl}^-(aq) + \mathrm{I}_2(s). $$Which species is the oxidizing agent?

Accepted Answer

$$\mathrm{Cl}_2$$

Question 8

Which oxide reacts with water to form an acidic solution?

Accepted Answer

$$\mathrm{SO}_3$$

Question 9

Which of the following best explains why alkali metals are good reducing agents?

Accepted Answer

They have low ionization energies and readily lose electrons.

Question 10

Which of the following statements about the trend in metallic character across a period is correct?

Accepted Answer

Metallic character decreases from left to right.

Question 11

A student observes that bromine is a liquid at room temperature, while chlorine is a gas and iodine is a solid. Based on periodic trends, what can be inferred about the boiling point of bromine?

Accepted Answer

It is higher than chlorine but lower than iodine.

Question 12

Which of the following best describes the trend in electron affinity across a period from left to right?

Accepted Answer

Electron affinity becomes more negative.

Question 13

Which of the following elements would you expect to have the largest atomic radius?

Accepted Answer

K

Question 14

Which of the following best explains the anomaly in ionization energy between Be and B?

Accepted Answer

Boron has a lower ionization energy because its electron is removed from a higher energy p-orbital.

Question 15

Which of the following oxides is amphoteric, reacting with both acids and bases?

Accepted Answer

$$\mathrm{Al}_2\mathrm{O}_3$$

Question 16

Which of the following best describes the trend in effective nuclear charge ($$Z_{	ext{eff}}) $$across a period?

Accepted Answer

$$Z_{	ext{eff}}$$ increases due to increasing nuclear charge with minimal additional shielding.

Question 17

Which of the following is the correct half-reaction for the reduction of oxygen in the reaction $$2\mathrm{Mg}(s) + \mathrm{O}_2(g) \rightarrow 2\mathrm{MgO}(s)$$?

Accepted Answer

$$\mathrm{O}_2(g) + 4e^- \rightarrow 2\mathrm{O}^{2-}(s)$$

Question 18

Which of the following substances is a good oxidizing agent?

Accepted Answer

$$\mathrm{O}_2$$

Question 19

Which of the following best describes the acid-base behavior of $$\mathrm{P}_4\mathrm{O}_{10}$$ when dissolved in water?

Accepted Answer

It forms an acidic solution.

Question 20

Which of the following best explains why halogens are strong oxidizing agents?

Accepted Answer

They have high electron affinities and readily gain electrons.

Lec 7 notes chem

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