Question 1

Which of the following statements best explains why the 4s orbital is filled before the 3d orbital in the electron configuration of potassium (K)?

Accepted Answer

Because the 4s orbital has a lower energy than the 3d orbital.

Question 2

According to the Pauli Exclusion Principle, which of the following is true for electrons in the same orbital?

Accepted Answer

They must have opposite spin quantum numbers $$m_s.$$

Question 3

Which of the following electron configurations represents an excited state of an aluminum atom ($$Z=13$$)?

Accepted Answer

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

Question 4

Which element has the largest atomic radius among the following: $$\mathrm{Na}$$, $$\mathrm{Li}$$, $$\mathrm{K}$$, $$\mathrm{Rb}$$?

Accepted Answer

$$\mathrm{Rb}$$

Question 5

What is the condensed electron configuration for $$\mathrm{Fe$$^{3+}$$}$$?

Accepted Answer

$$[\mathrm{Ar}]\ 3d^5$

Question 6

Which of the following ions has the smallest radius?

Accepted Answer

$$\mathrm{Na^+}$$

Question 7

Which of the following best describes the trend in ionization energy across a period (left to right) in the periodic table?

Accepted Answer

Ionization energy increases due to increasing effective nuclear charge.

Question 8

Which of the following elements is expected to have the most exothermic electron affinity?

Accepted Answer

$$\mathrm{F}$$

Question 9

A neutral atom of sulfur ($$\mathrm{S}) $$has how many unpaired electrons in its ground state?

Accepted Answer

2

Question 10

Which of the following statements about effective nuclear charge ($$Z_{\mathrm{eff}}) is $$correct?

Accepted Answer

$$Z_{\mathrm{eff}}$$ increases across a period from left to right.

Question 11

Which of the following is the correct order of increasing atomic radius for the elements $$\mathrm{S}$$, $$\mathrm{Cl}$$, $$\mathrm{Na}$$, and $$\mathrm{Li}$$?

Accepted Answer

$$\mathrm{Cl} \u003c \mathrm{S} \u003c \mathrm{Li} \u003c \mathrm{Na}$$

Question 12

Which of the following elements is most likely to be paramagnetic in its ground state?

Accepted Answer

$$\mathrm{O}$$

Question 13

Which of the following is the correct condensed electron configuration for $$\mathrm{Sn} ($$tin)?

Accepted Answer

$$[\mathrm{Kr}]\ 5s^2$\ 4d$$^{10}$$\ 5p^2$

Question 14

Which of the following best explains why cations are smaller than their parent atoms?

Accepted Answer

Cations have more protons than electrons, increasing the effective nuclear charge and pulling electrons closer.

Question 15

Which of the following is the correct order of filling for the following orbitals?

Accepted Answer

$$3p \rightarrow 4s \rightarrow 3d \rightarrow 4p$$

Question 16

Which of the following transition elements is an exception to the expected electron configuration due to a half-filled or fully filled $$d$$ subshell?

Accepted Answer

$$\mathrm{Cu}$$

Question 17

Which of the following best describes the trend in reactivity for Group 1A (alkali metals) as you move down the group?

Accepted Answer

Reactivity increases because ionization energy decreases.

Question 18

Which of the following statements about electron configuration of ions is correct?

Accepted Answer

Transition metal cations lose $$s$$ electrons before $$d$$ electrons.

Question 19

Which of the following best explains why atomic radii increase from top to bottom within a group?

Accepted Answer

Because additional energy levels are added, increasing the distance from the nucleus.

Question 20

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

Accepted Answer

$$\mathrm{F}$$

Periodic Properties of Elements: Electron Arrangement and Atomic Trends

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