Question 1

Which of the following statements 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 electrons closer to the nucleus.

Question 2

Which set of quantum numbers is NOT allowed for an electron in an atom?

Accepted Answer

$$n = 2,\ l = 2,\ m_l = 1,\ m_s = +\frac{1}{2}$$

Question 3

Which element has the highest first ionization energy?

Accepted Answer

Neon ($$Ne)$$

Question 4

Which of the following ions has the largest ionic radius?

Accepted Answer

$$O^{2-}$$

Question 5

Which electron configuration represents a transition metal in its ground state?

Accepted Answer

$$[Ar] 4s^2$ 3d^5$

Question 6

Which of the following best describes the shielding effect?

Accepted Answer

The reduction in effective nuclear charge on outer electrons due to inner electrons.

Question 7

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

Accepted Answer

Cesium ($$Cs)$$

Question 8

Which of the following electron configurations is an exception to the Aufbau principle?

Accepted Answer

$$[Ar] 4s^1$ 3d^5$ for Chromium (Cr$)

Question 9

According to Coulomb's Law, which pair of charged particles will experience the greatest attractive force?

Accepted Answer

A $$+2$$ and $$-1$$ charge separated by $$100\ \mathrm{pm}$$

Question 10

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

Accepted Answer

Fluorine ($$F)$$

Question 11

Which of the following ions is isoelectronic with Argon ($$Ar$$)?

Accepted Answer

$$Cl^-$$

Question 12

Which of the following elements would you expect to have the smallest atomic radius?

Accepted Answer

Chlorine ($$Cl)$$

Question 13

Which of the following best describes the trend in ionization energy across a period?

Accepted Answer

Ionization energy increases due to increased effective nuclear charge.

Question 14

Which of the following elements has a half-filled $$d$$ subshell in its ground state?

Accepted Answer

Chromium ($$Cr)$$

Question 15

Which of the following electron configurations represents a noble gas?

Accepted Answer

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

Question 16

Which of the following best explains why $$F^- is $$larger than $$Na^+$$, even though both are isoelectronic?

Accepted Answer

$$Na^+$$ has more protons, so it pulls electrons closer.

Question 17

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

Accepted Answer

Magnesium ($$Mg)$$

Question 18

Which of the following best describes the relationship between atomic number and effective nuclear charge ($$Z_{eff}) $$across a period?

Accepted Answer

$$Z_{eff}$$ increases as atomic number increases.

Question 19

Which of the following elements is a main-group element?

Accepted Answer

Calcium ($$Ca)$$

Question 20

Which of the following best describes the trend in electron affinity across a period?

Accepted Answer

Electron affinity becomes more negative (more exothermic).

Chapter 3: Periodic Properties of the Elements – Study Notes

Study Guide - Practice Questions