Question 1

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

Accepted Answer

The effective nuclear charge increases, pulling valence electrons closer to the nucleus.

Question 2

Which element would you expect to have the highest first ionization energy?

Accepted Answer

Fluorine ($$F)$$

Question 3

What is the electron configuration for a $$Cl^-$$ ion?

Accepted Answer

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

Question 4

Which of the following ions is isoelectronic with $$Ar$$?

Accepted Answer

$$K^+$$

Question 5

Why does the first ionization energy decrease as you move down a group in the periodic table?

Accepted Answer

Valence electrons are farther from the nucleus and experience more shielding.

Question 6

Which of the following elements is most likely to form a $$2+$$ cation?

Accepted Answer

Calcium ($$Ca)$$

Question 7

Which of the following statements about transition metals is correct?

Accepted Answer

Some transition metals have irregular electron configurations due to increased stability of half-filled or fully filled $$d$$ sublevels.

Question 8

Which of the following best describes Hund’s Rule?

Accepted Answer

Electrons occupy degenerate orbitals singly before pairing.

Question 9

Which of the following sets of ions and atoms is arranged in order of increasing radius?

Accepted Answer

$$Ca^{2+}$$ \u003c K^+ \u003c Cl^- \u003c $$S^{2-}$$

Question 10

Which of the following elements is expected to have the most metallic character?

Accepted Answer

Rubidium ($$Rb)$$

Question 11

Which of the following is the correct noble gas core electron configuration for $$Cu$$?

Accepted Answer

$$[Ar] 4s^1$ 3d$$^{10}$$

Question 12

Which of the following best explains why $$O$$ has a lower first ionization energy than $$N$$?

Accepted Answer

Oxygen has a paired electron in a $$2p$$ orbital, increasing electron-electron repulsion.

Question 13

Which of the following elements has the most exothermic (most negative) electron affinity?

Accepted Answer

Sulfur ($$S)$$

Question 14

Which of the following is a property of metals?

Accepted Answer

They are malleable and ductile.

Question 15

Which of the following ions is paramagnetic?

Accepted Answer

$$Fe^{2+}$$

Question 16

Which of the following best describes the trend in density for elements in a group as you move down the periodic table?

Accepted Answer

Density generally increases due to increasing atomic mass.

Question 17

Which of the following is the correct order of filling for the first four energy sublevels according to the Aufbau principle?

Accepted Answer

$$1s \rightarrow 2s \rightarrow 2p \rightarrow 3s$$

Question 18

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

Accepted Answer

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

Question 19

Which of the following elements is a metalloid?

Accepted Answer

Silicon ($$Si)$$

Question 20

Which of the following best describes the electron configuration for $$Cr ($$Chromium)?

Accepted Answer

$$[Ar] 4s^1$ 3d^5$

Periodic Properties of the Elements: Structure, Trends, and Electron Configurations

Study Guide - Practice Questions