$$Z_{\text{eff}}$$ increases from left to right

Question 1

Which scientist is credited with establishing the concept of atomic number as the basis for the periodic property of elements?

Accepted Answer

Henry Moseley

Question 2

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

Accepted Answer

$$Z_{	ext{eff}}$$ increases from left to right

Question 3

Which equation correctly represents the first ionization energy of aluminum?

Accepted Answer

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

Question 4

Arrange the following ions in order of decreasing radius: $$\mathrm{Ca}$$, $$\mathrm{Ca}^{2+}$$, $$\mathrm{Mg}^{2+}.$$

Accepted Answer

$$\mathrm{Ca} \u003e \mathrm{Ca}^{2+} \u003e \mathrm{Mg}^{2+}$$

Question 5

Which of the following statements about cations and anions is correct?

Accepted Answer

Cations are smaller than their parent atoms; anions are larger.

Question 6

Which of the following correctly represents the second ionization of calcium?

Accepted Answer

$$\mathrm{Ca}^+ (g) \rightarrow \mathrm{Ca}^{2+} (g) + e^-$$

Question 7

Which of the following best explains why the first ionization energy generally increases across a period?

Accepted Answer

Effective nuclear charge increases, holding electrons more tightly.

Question 8

Which of the following is true about the electron affinity ($$EA) of $$elements?

Accepted Answer

Electron affinity is typically exothermic (negative) for most elements.

Question 9

Which group in the periodic table has elements with a full $$s$$ sublevel, leading to an exception in the general trend of electron affinity?

Accepted Answer

Group 2A

Question 10

In an isoelectronic series, which ion will have the smallest radius?

Accepted Answer

The ion with the largest nuclear charge

Question 11

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

Accepted Answer

Atomic radius increases

Question 12

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

Accepted Answer

$$Z_{	ext{eff}} = Z - S$$

Question 13

Which of the following best explains why anions are larger than their parent atoms?

Accepted Answer

Anions have more electrons, increasing electron-electron repulsion.

Question 14

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

Accepted Answer

Neon ($$\mathrm{Ne})$$

Question 15

Which of the following is a correct statement about the removal of electrons in the formation of cations?

Accepted Answer

Electrons are lost from the highest energy level (largest $$n$$ value) first.

Question 16

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

Accepted Answer

It decreases

Question 17

Which of the following is the best explanation for the irregularities in the general trend of ionization energy?

Accepted Answer

The addition of a valence electron to a new or higher energy sublevel

Question 18

Which of the following is the best definition of the bonding atomic radius?

Accepted Answer

Half the distance between nuclei in a bond

Question 19

Which of the following is a real-world application of ionization energy?

Accepted Answer

Predicting the reactivity of alkali metals in water

Question 20

Which of the following best describes the trend in the bonding atomic radius across a period?

Accepted Answer

It decreases from left to right

Periodic Properties of the Elements: Atomic Structure and Trends

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