Q: Across a period from left to right, what is the general trend in atomic radius and why?

Atomic radius decreases because $$Z_{\text{eff}}$$ increases, pulling electrons closer to the nucleus.

Q: Which of the following best describes the trend in electron affinity (EA) across a period from left to right?

EA becomes more negative (increases) due to increased $$Z_{\text{eff}}$$ and stronger attraction for added electrons.

Q: Which of the following best describes the trend in metallic character across a period from left to right?

Metallic character decreases due to increased $$Z_{\text{eff}}$$ and higher ionization energies.

Question 1

Which of the following best explains why the atomic radius of sodium (Na) is larger than that of lithium (Li)?

Accepted Answer

Sodium has more electron shells than lithium, increasing the distance between the nucleus and the outermost electron.

Question 2

Across a period from left to right, what is the general trend in atomic radius and why?

Accepted Answer

Atomic radius decreases because $$Z_{	ext{eff}}$$ increases, pulling electrons closer to the nucleus.

Question 3

Which element would you expect to have the highest first ionization energy ($$IE_1) in $$period 2?

Accepted Answer

Neon (Ne)

Question 4

Why is the first ionization energy of beryllium (Be) higher than that of boron (B), even though B is to the right of Be in the same period?

Accepted Answer

Beryllium has a filled s subshell, which is more stable and harder to remove an electron from.

Question 5

Which of the following reactions represents the addition of an electron to a chlorine atom, and what is the associated energy change called?

Accepted Answer

$$\mathrm{Cl}(g) + e^- \rightarrow \mathrm{Cl}^-(g)$$; this is called electron affinity.

Question 6

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

Accepted Answer

EA becomes more negative (increases) due to increased $$Z_{	ext{eff}}$$ and stronger attraction for added electrons.

Question 7

Which of the following elements is most likely to act as a good reducing agent in a redox reaction?

Accepted Answer

Potassium (K)

Question 8

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 9

Which oxide would you expect to form a basic solution when dissolved in water?

Accepted Answer

$$\mathrm{Na}_2\mathrm{O}$$

Question 10

A sample of magnesium reacts with oxygen to form $$\mathrm{MgO}. $$Which statement best describes the electron transfer in this reaction?

Accepted Answer

Magnesium loses electrons to oxygen, forming $$\mathrm{Mg}^{2+}$$ and $$\mathrm{O}^{2-}$$ ions.

Question 11

Which of the following best explains why the third ionization energy ($$IE_3) of $$magnesium is much higher than its first and second ionization energies?

Accepted Answer

The third electron is removed from a core shell, which is much closer to the nucleus and more tightly bound.

Question 12

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

Accepted Answer

Metallic character decreases due to increased $$Z_{	ext{eff}}$$ and higher ionization energies.

Question 13

Which of the following statements about the periodic trends in ionization energy is correct?

Accepted Answer

Ionization energy decreases down a group and increases across a period.

Question 14

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

Accepted Answer

They have high electron affinities and readily gain electrons to form anions.

Question 15

Which of the following oxides is amphoteric, meaning it can react as both an acid and a base?

Accepted Answer

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

Question 16

Which of the following best describes the trend in atomic radius down a group?

Accepted Answer

Atomic radius increases due to the addition of electron shells.

Question 17

Which of the following elements would have the most negative electron affinity?

Accepted Answer

Fluorine (F)

Question 18

Which of the following best explains why alkali metals react vigorously with water?

Accepted Answer

They have low ionization energies and readily lose their outermost electron.

Question 19

Which of the following is the correct order of increasing first ionization energy ($$IE_1) $$for the elements Na, Mg, and Al?

Accepted Answer

Na \u003c Mg \u003c Al

Periodic Properties of the Elements: Trends and Chemical Behavior

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