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

$$Al^{3+}$$ \u003c $$Mg^{2+}$$ \u003c 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

$$Ba \u003e Mg \u003e Be$$

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

$$Na \u003c Mg \u003c Al$$

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

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