Metallic character decreases from left to right.

$Fe^{2+}$ has a lower ionization energy for the third electron than $Mn^{2+}$.

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

Atomic radius increases down a group.

Question 1

Which of the following statements best explains why atomic radius decreases across a period from left to right?

Accepted Answer

The effective nuclear charge ($Z_{eff}$) increases, pulling electrons closer to the nucleus.

Question 2

A neutral atom of calcium has 20 electrons. What is its ground-state electron configuration?

Accepted Answer

$1s^2 2s^2 2p^6 3s^2 3p^6 4s^2$

Question 3

Which of the following ions is isoelectronic with neon ($Ne$)?

Accepted Answer

$Na^+$

Question 4

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

Accepted Answer

$Al^{3+} < Mg^{2+} < Na^+$

Question 5

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

Accepted Answer

Phosphorus ($P$)

Question 6

What is the electron configuration of $F^-$?

Accepted Answer

$1s^2 2s^2 2p^6$

Question 7

Which of the following pairs is written in order of decreasing atomic radius?

Accepted Answer

$Ba > Mg > Be$

Question 8

Why does the ionic radius of an anion increase compared to its neutral atom?

Accepted Answer

The addition of electrons increases electron-electron repulsion, expanding the electron cloud.

Question 9

Which of the following oxides is amphoteric?

Accepted Answer

$Al_2O_3$

Question 10

Which species has the more favorable (more negative) electron affinity?

Accepted Answer

Fluorine ($F$)

Question 11

Which of the following ions is smaller: $Fe^{2+}$ or $Fe^{3+}$?

Accepted Answer

$Fe^{3+}$

Question 12

What is the correct order of increasing first ionization energy for the following elements: $Na$, $Mg$, $Al$?

Accepted Answer

$Na < Mg < Al$

Question 13

Which of the following best describes the trend in metallic character across a period?

Accepted Answer

Metallic character decreases from left to right.

Question 14

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

Accepted Answer

$O^{2-}$

Question 15

Which element is diamagnetic in its ground state?

Accepted Answer

Calcium ($Ca$)

Question 16

Which of the following best explains why $Fe^{2+}$ is more easily oxidized to $Fe^{3+}$ than $Mn^{2+}$ to $Mn^{3+}$?

Accepted Answer

$Fe^{2+}$ has a lower ionization energy for the third electron than $Mn^{2+}$.

Question 17

Which of the following equations represents the first ionization energy of sodium?

Accepted Answer

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

Question 18

Which of the following best describes the trend in atomic radius down a group?

Accepted Answer

Atomic radius increases down a group.

Question 19

Which of the following is the correct electron configuration for $Co^{2+}$?

Accepted Answer

$[Ar] 3d^7$

Periodic Relationships Among the Elements: Electron Configurations, Ion Formation, and Periodic Trends

Study Guide - Practice Questions