Question 1

Which formula is used to calculate the effective nuclear charge ($$Z_{eff}) $$experienced by an electron in a multi-electron atom?

Accepted Answer

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

Question 2

As you move from left to right across a period in the periodic table, what happens to the effective nuclear charge ($$Z_{eff}) $$and why?

Accepted Answer

$$Z_{eff}$$ increases because the number of protons increases while shielding remains relatively constant.

Question 3

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

Accepted Answer

Atomic radius increases due to the addition of electron shells.

Question 4

What happens to the atomic radius as you move left to right across a period, and why?

Accepted Answer

Atomic radius decreases because $$Z_{eff}$$ increases, pulling electrons closer.

Question 5

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

Accepted Answer

$$Mg^{2+}$$

Question 6

When an atom gains electrons to form an anion, what generally happens to its size?

Accepted Answer

The size increases due to increased electron-electron repulsion.

Question 7

Which equation correctly represents the first ionization energy of sodium?

Accepted Answer

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

Question 8

Why does ionization energy generally increase as you move left to right across a period?

Accepted Answer

Because $$Z_{eff}$$ increases, making it harder to remove an electron.

Question 9

What is the trend in ionization energy as you move down a group, and why?

Accepted Answer

Ionization energy decreases because atomic radius increases and electrons are farther from the nucleus.

Question 10

Which equation represents the electron affinity of chlorine?

Accepted Answer

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

Question 11

What does it mean for an element to have an exothermic electron affinity value?

Accepted Answer

Energy is released when the atom gains an electron.

Question 12

Why do chemists use the terms 'favorable' and 'unfavorable' when discussing electron affinity?

Accepted Answer

To indicate whether the process releases energy (favorable) or requires energy (unfavorable).

Question 13

What is the trend in electron affinity as you move left to right across a period?

Accepted Answer

Electron affinity becomes more exothermic because atoms more readily accept electrons.

Question 14

What is the trend in electron affinity as you move down a group?

Accepted Answer

Electron affinity becomes less exothermic because added electrons are farther from the nucleus.

Question 15

Which property is NOT characteristic of alkali metals?

Accepted Answer

High ionization energy

Question 16

Which of the following is a typical property of alkaline earth metals?

Accepted Answer

Form $$+2$$ ions and are less reactive than alkali metals

Question 17

Which statement best describes the halogens?

Accepted Answer

They are highly reactive nonmetals and readily form $$-1$$ ions.

Question 18

Which property is most characteristic of noble gases?

Accepted Answer

They are chemically inert due to a full valence shell.

Question 19

A patient is exposed to a toxic halogen gas. Which property of halogens explains their high reactivity and potential danger?

Accepted Answer

Halogens have high electron affinities and readily gain electrons to form $$-1$$ ions.

Question 20

Which of the following best explains why $$Na^{+} is $$smaller than $$F^{-}$$, even though both are isoelectronic?

Accepted Answer

$$Na^{+}$$ has more protons, so the electrons are pulled closer to the nucleus.

Periodic Trends and Properties of Elements: Study Notes

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