Question 1

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

Accepted Answer

The number of protons increases, increasing the effective nuclear charge, which pulls electrons closer to the nucleus.

Question 2

Which of the following electron configurations represents a magnesium ion, $$\mathrm{Mg$$^{2+}$$}$$?

Accepted Answer

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

Question 3

Which of the following statements about ionization energy is correct?

Accepted Answer

Ionization energy generally increases across a period due to increasing effective nuclear charge.

Question 4

A neutral atom of sulfur ($$\mathrm{S}) $$has the electron configuration $$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^4. $$How many unpaired electrons does it have?

Accepted Answer

2

Question 5

Which of the following elements is expected to have the highest first ionization energy?

Accepted Answer

Neon ($$\mathrm{Ne})$$

Question 6

Which of the following best describes the electron configuration of a chloride ion ($$\mathrm{Cl^-}$$)?

Accepted Answer

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

Question 7

Which of the following statements about the periodic table is FALSE?

Accepted Answer

Noble gases are found in group 8A (18) and are highly reactive.

Question 8

Which of the following ions is isoelectronic with neon ($$\mathrm{Ne}$$)?

Accepted Answer

$$\mathrm{F^-}$$

Question 9

Which of the following best explains why the second ionization energy of sodium is much higher than the first?

Accepted Answer

The second electron is removed from a noble gas core, which is much more stable and tightly bound.

Question 10

Which of the following elements would you expect to have the most metallic character?

Accepted Answer

Cesium ($$\mathrm{Cs})$$

Question 11

Which of the following correctly describes the trend in atomic radius for main-group elements?

Accepted Answer

Atomic radius increases down a group and decreases across a period.

Question 12

Which of the following statements about electron configurations is correct?

Accepted Answer

Electrons fill orbitals of lowest energy first, following the Aufbau principle.

Question 13

Which of the following elements has the electron configuration $$[\mathrm{Ar}]\ 4s^2$\ 3d$$^{10}$$\ 4p^5$?

Accepted Answer

Bromine ($$\mathrm{Br})$$

Question 14

Which of the following best describes the Pauli Exclusion Principle?

Accepted Answer

No two electrons in an atom can have the same set of four quantum numbers.

Question 15

Which of the following ions is expected to be paramagnetic?

Accepted Answer

$$\mathrm{Fe$$^{3+}$$}$$

Question 16

Which of the following statements about the formation of ions is correct?

Accepted Answer

Alkali metals form $$+1$$ cations by losing one electron.

Question 17

Which of the following best explains why transition metals often have variable oxidation states?

Accepted Answer

Their d and s electrons are close in energy, allowing for the loss of different numbers of electrons.

Question 18

Which of the following is the correct order of sublevel energy (from lowest to highest) for the first four sublevels in a multielectron atom?

Accepted Answer

$$1s \u003c 2s \u003c 2p \u003c 3s$$

Question 19

Which of the following best describes the trend in electron affinity for main-group elements?

Accepted Answer

Electron affinity becomes more negative across a period (left to right).

Chapter 3: Periodic Properties

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