Q: What is the effective nuclear charge ($$Z_{\text{eff}}) $$experienced by the valence electron in a sodium atom ($$\text{Na}$$), assuming the screening constant $$S is $$equal to the number of core electrons?

$$Z_{\text{eff}} = 11 - 10 = 1$$

Q: Arrange the following ions in order of increasing ionic radius: $$\text{O}^{2-}$$, $$\text{F}^-$$, $$\text{Na}^+$$, $$\text{Mg}^{2+}$$, $$\text{Al}^{3+}.$$

$$\text{Al}^{3+} \u003c \text{Mg}^{2+} \u003c \text{Na}^+ \u003c \text{F}^- \u003c \text{O}^{2-}$$

Q: Which of the following equations correctly represents the reaction of cesium with water?

$$2\,\text{Cs}(s) + 2\,\text{H}_2\text{O}(l) \rightarrow 2\,\text{CsOH}(aq) + \text{H}_2(g)$$

Q: Which of the following is the correct balanced equation for the reaction of strontium with water?

$$\text{Sr}(s) + 2\,\text{H}_2\text{O}(l) \rightarrow \text{Sr(OH)}_2(aq) + \text{H}_2(g)$$

Question 1

Which scientist is credited with developing the concept of atomic number, which led to the modern arrangement of the periodic table?

Accepted Answer

Henry Moseley

Question 2

What is the effective nuclear charge ($$Z_{	ext{eff}}) $$experienced by the valence electron in a sodium atom ($$	ext{Na}$$), assuming the screening constant $$S is $$equal to the number of core electrons?

Accepted Answer

$$Z_{	ext{eff}} = 11 - 10 = 1$$

Question 3

Which of the following correctly describes the trend in atomic radius across a period from left to right?

Accepted Answer

Atomic radius decreases due to increasing effective nuclear charge.

Question 4

Arrange the following ions in order of increasing ionic radius: $$	ext{O}^{2-}$$, $$	ext{F}^-$$, $$	ext{Na}^+$$, $$	ext{Mg}^{2+}$$, $$	ext{Al}^{3+}.$$

Accepted Answer

$$	ext{Al}^{3+} \u003c 	ext{Mg}^{2+} \u003c 	ext{Na}^+ \u003c 	ext{F}^- \u003c 	ext{O}^{2-}$$

Question 5

Which of the following statements about ionization energy is correct?

Accepted Answer

Ionization energy generally increases across a period.

Question 6

Which element would have the largest jump in ionization energy between the second and third ionization energies?

Accepted Answer

Magnesium ($$	ext{Mg})$$

Question 7

Which of the following best explains why cations are smaller than their parent atoms?

Accepted Answer

Cations have fewer electrons, reducing electron-electron repulsion.

Question 8

Which of the following equations correctly represents the reaction of cesium with water?

Accepted Answer

$$2\,	ext{Cs}(s) + 2\,	ext{H}_2	ext{O}(l) ightarrow 2\,	ext{CsOH}(aq) + 	ext{H}_2(g)$$

Question 9

Which of the following best describes the trend in metallic character across the periodic table?

Accepted Answer

Metallic character decreases from left to right across a period.

Question 10

Which of the following elements is a metalloid?

Accepted Answer

Silicon

Question 11

Which of the following best explains why the electron affinity of noble gases is close to zero or positive?

Accepted Answer

Noble gases have a full valence shell, so adding an electron is energetically unfavorable.

Question 12

Which of the following is the correct electron configuration for $$	ext{Cr}^{3+}$$?

Accepted Answer

[Ar] $$3d^3$$

Question 13

Which of the following statements about the chemical properties of metals and nonmetals is correct?

Accepted Answer

Metal oxides tend to be basic.

Question 14

Which of the following elements has the most negative electron affinity?

Accepted Answer

Fluorine

Question 15

Which of the following best explains the large jump in ionization energy when removing a core electron?

Accepted Answer

Core electrons are closer to the nucleus and experience a much higher effective nuclear charge.

Question 16

Which of the following is the correct balanced equation for the reaction of strontium with water?

Accepted Answer

$$	ext{Sr}(s) + 2\,	ext{H}_2	ext{O}(l) ightarrow 	ext{Sr(OH)}_2(aq) + 	ext{H}_2(g)$$

Question 17

Which of the following elements has the smallest first ionization energy?

Accepted Answer

Potassium ($$	ext{K})$$

Question 18

Which of the following best describes the electron configuration of $$	ext{Ag}^+$$?

Accepted Answer

[Kr] $$4d^{10}$$

Question 19

Which of the following statements about isoelectronic ions is correct?

Accepted Answer

Isoelectronic ions have the same number of electrons.

Question 20

Which of the following best explains why halogens are highly reactive?

Accepted Answer

They have a nearly full valence shell and high electron affinity.

Periodic Properties of the Elements: Structure, Trends, and Reactivity

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