Increase in effective nuclear charge ($$Z_{\text{eff}})$$

$$2\text{Na}(s) + 2\text{H}_2\text{O}(l) \rightarrow 2\text{NaOH}(aq) + \text{H}_2(g)$$

Question 1

Which of the following statements best describes the main difference between Mendeleev’s periodic table and the modern periodic table?

Accepted Answer

Mendeleev arranged elements by increasing atomic mass, while the modern table arranges them by increasing atomic number.

Question 2

Which property is primarily responsible for the decrease in atomic radius across a period from left to right?

Accepted Answer

Increase in effective nuclear charge ($$Z_{	ext{eff}})$$

Question 3

Which equation correctly represents the calculation of effective nuclear charge ($$Z_{	ext{eff}}$$)?

Accepted Answer

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

Question 4

Which of the following ions is the smallest in an isoelectronic series: $$	ext{Na}^+$$, $$	ext{Mg}^{2+}$$, $$	ext{Al}^{3+}$$, $$	ext{F}^-$$?

Accepted Answer

$$	ext{Al}^{3+}$$

Question 5

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

Accepted Answer

The effective nuclear charge increases, making electrons harder to remove.

Question 6

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

Accepted Answer

Fluorine ($$	ext{F})$$

Question 7

Which of the following reactions demonstrates the typical behavior of an alkali metal with water?

Accepted Answer

$$2	ext{Na}(s) + 2	ext{H}_2	ext{O}(l) ightarrow 2	ext{NaOH}(aq) + 	ext{H}_2(g)$$

Question 8

Which of the following statements about metals is FALSE?

Accepted Answer

Metal oxides tend to be acidic.

Question 9

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

Accepted Answer

Metallic character increases down a group and decreases across a period.

Question 10

Which of the following best explains why noble gases are generally unreactive?

Accepted Answer

They have completely filled s and p sub-shells.

Question 11

Which of the following is a correct statement about the periodic trend in atomic radius?

Accepted Answer

Atomic radius decreases from left to right across a period and increases from top to bottom within a group.

Question 12

Which of the following best describes the behavior of nonmetal oxides in water?

Accepted Answer

They form acidic solutions.

Question 13

Which of the following elements is most likely to form a $$2+$$ ion?

Accepted Answer

Magnesium ($$	ext{Mg})$$

Question 14

Which of the following best explains the sharp increase in ionization energy after removal of all valence electrons?

Accepted Answer

The next electron is removed from a lower energy shell (core electron) closer to the nucleus.

Question 15

Which of the following is a metalloid?

Accepted Answer

Silicon

Question 16

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

Accepted Answer

Electron affinity becomes more exothermic (more negative) from left to right.

Question 17

Which of the following reactions is an example of a nonmetal reacting with a metal to form an ionic compound?

Accepted Answer

$$2	ext{Al}(s) + 3	ext{Br}_2(l) ightarrow 2	ext{AlBr}_3(s)$$

Question 18

Which of the following elements is most likely to be found as a diatomic molecule in nature?

Accepted Answer

Chlorine

Question 19

Which of the following best explains why alkali metals are not found in their elemental form in nature?

Accepted Answer

They are highly reactive and readily lose their single valence electron.

Question 20

Which of the following best describes the trend in reactivity for Group 2A (alkaline earth) metals with water?

Accepted Answer

Reactivity increases down the group.

Chapter 7: Periodic Properties of the Elements – Study Notes

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