Question 1

Which of the following ions has the smallest atomic radius?

Accepted Answer

$\mathrm{Be^{2+}}$

Question 2

As you move from left to right across a period in the periodic table, what generally happens to the atomic radius and why?

Accepted Answer

Atomic radius decreases because the nuclear charge increases, pulling electrons closer.

Question 3

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

Accepted Answer

The effective nuclear charge increases, holding electrons more tightly.

Question 4

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

Accepted Answer

$\mathrm{Cl}$

Question 5

Why does atomic radius increase as you move down a group in the periodic table?

Accepted Answer

Electrons are added to higher principal energy levels, increasing the size of the electron cloud.

Question 6

Which of the following statements about electron affinity is correct?

Accepted Answer

Electron affinity becomes more negative across a period from left to right.

Question 7

A student claims that $\mathrm{K^+}$ is larger than $\mathrm{Ca^{2+}}$ because potassium is to the left of calcium in the periodic table. Is this correct? Why or why not?

Accepted Answer

No, because $\mathrm{Ca^{2+}}$ has a higher charge and thus a smaller radius.

Question 8

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

Accepted Answer

It decreases because electrons are farther from the nucleus and more shielded.

Question 9

Which of the following elements would require the most energy to remove its outermost electron?

Accepted Answer

$\mathrm{Ne}$

Question 10

A plot of atomic radius versus atomic number shows periodic peaks. What do these peaks correspond to?

Accepted Answer

Alkali metals

Question 11

Which of the following best explains why noble gases have very low (or positive) electron affinities?

Accepted Answer

They have a full valence shell and adding an electron would require a new energy level.

Question 12

Which of the following ions is isoelectronic with $\mathrm{Ne}$ and has the largest radius?

Accepted Answer

$\mathrm{O^{2-}}$

Question 13

If the electron affinity of an element is negative, what does this indicate?

Accepted Answer

Energy is released when an electron is added.

Question 14

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

Accepted Answer

It decreases due to increased nuclear charge.

Question 15

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

Accepted Answer

$\mathrm{Ne}$

Question 16

A patient is exposed to a gas that has a very high electron affinity. What is a likely property of this gas?

Accepted Answer

It is likely a halogen.

Question 17

Which of the following best explains why $\mathrm{Mg^{2+}}$ is much smaller than $\mathrm{Mg}$?

Accepted Answer

$\mathrm{Mg^{2+}}$ has lost two electrons, reducing electron-electron repulsion and the size of the electron cloud.

Question 18

Which of the following statements about periodic trends is correct?

Accepted Answer

Ionization energy decreases down a group.

Question 19

Which of the following best explains why it is harder to remove a second electron from a $\mathrm{Na^+}$ ion than from a neutral $\mathrm{Na}$ atom?

Accepted Answer

The $\mathrm{Na^+}$ ion has a higher effective nuclear charge acting on fewer electrons.

Question 20

Which of the following best describes the relationship between atomic number and atomic radius for the alkali metals?

Accepted Answer

Atomic radius increases as atomic number increases.

Periodic Properties of the Elements: Atomic Radius, Ionization Energy, and Electron Affinity

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