$$Cl(g) + e^- \rightarrow Cl^-(g)$$, $$EA = -349\ \text{kJ}$$

Question 1

Which of the following statements best explains why Mendeleev's periodic table was considered revolutionary for its time?

Accepted Answer

It predicted the existence and properties of undiscovered elements based on periodic trends.

Question 2

Henry Moseley’s work with X-rays led to a new basis for the periodic table. What property did he use to arrange the elements?

Accepted Answer

Atomic number

Question 3

Which equation correctly represents the effective nuclear charge ($$Z_{	ext{eff}}) $$experienced by a valence electron?

Accepted Answer

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

Question 4

Which trend is observed for the bonding atomic radius as you move from left to right across a period in the periodic table?

Accepted Answer

It decreases due to increasing effective nuclear charge.

Question 5

Which of the following ions is the largest in the isoelectronic series: $$O^{2-}$$, $$F^{-}$$, $$Na^{+}$$, $$Mg^{2+}$$?

Accepted Answer

$$O^{2-}$$

Question 6

Why are cations smaller than their parent atoms?

Accepted Answer

Cations lose their outermost electron(s), reducing electron-electron repulsion and the size of the electron cloud.

Question 7

Which of the following best describes the general trend in first ionization energy ($$I_1) $$across a period?

Accepted Answer

It increases due to increasing effective nuclear charge.

Question 8

Which element would you expect to have the highest first ionization energy among the following: $$Na$$, $$Mg$$, $$Al$$, $$Si$$?

Accepted Answer

$$Si$$

Question 9

Which of the following best explains the irregularity in the trend of first ionization energy between nitrogen and oxygen?

Accepted Answer

Oxygen’s added electron pairs up in a 2p orbital, increasing electron-electron repulsion and lowering the ionization energy.

Question 10

Which of the following reactions represents an exothermic electron affinity process?

Accepted Answer

$$Cl(g) + e^- ightarrow Cl^-(g)$$, $$EA = -349\ 	ext{kJ}$$

Question 11

Which of the following statements about metals is FALSE?

Accepted Answer

Most metals are dull and brittle.

Question 12

A sample of sodium metal is placed in water and reacts vigorously. Which property of sodium best explains this behavior?

Accepted Answer

Low ionization energy

Question 13

Which of the following best describes the chemical nature of most nonmetal oxides?

Accepted Answer

They are acidic and react with bases.

Question 14

Which of the following is a property of metalloids that makes them useful in computer chips?

Accepted Answer

They are electrical semiconductors.

Question 15

Which of the following electron configurations represents the $$Fe^{2+}$$ ion?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^2$$ $$3p^6$$ $$3d^6$$

Question 16

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

Accepted Answer

They are highly reactive and readily form compounds.

Question 17

Which of the following oxides is formed when potassium reacts with oxygen?

Accepted Answer

$$KO_2 ($$superoxide)

Question 18

Which group in the periodic table contains elements that are all gases at room temperature and have very low chemical reactivity?

Accepted Answer

Group 8A (noble gases)

Question 19

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

Accepted Answer

Metallic character increases due to decreasing ionization energy.

Chapter 7: Periodic Properties of the Elements – Study Notes

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