Question 1

Which of the following correctly describes the electron configuration for a ground-state neutral atom of chlorine (Cl)?

Accepted Answer

$$[Ne] 3s^2$ 3p^5$

Question 2

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

Accepted Answer

The number of protons increases, pulling electrons closer to the nucleus.

Question 3

Which of the following ions is isoelectronic with neon ($$Ne$$)?

Accepted Answer

$$F^-$$

Question 4

Which of the following statements about transition metal electron configurations is correct?

Accepted Answer

The $$4s$$ orbital is filled before the $$3d$$ orbital because it is lower in energy.

Question 5

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

Accepted Answer

Neon ($$Ne)$$

Question 6

A magnesium atom ($$Mg) $$loses two electrons to form $$Mg^{2+}. $$What is the electron configuration of $$Mg^{2+}$$?

Accepted Answer

$$[Ne]$$

Question 7

Which of the following best explains why sodium ($$Na) $$forms a $$1+$$ ion and not a $$2+$$ ion?

Accepted Answer

Removing a second electron would require breaking into a core electron shell, which requires much more energy.

Question 8

Which of the following ions is expected to be paramagnetic?

Accepted Answer

$$Fe^{3+}$$ with configuration $$[Ar] 3d^5$

Question 9

Which of the following statements about metallic character is correct?

Accepted Answer

Metallic character increases down a group and decreases across a period.

Question 10

Which of the following best describes the trend in ionic radius for isoelectronic species?

Accepted Answer

For isoelectronic species, the more positive the charge, the smaller the ionic radius.

Question 11

Which of the following elements is most likely to form an anion with a $$1-$$ charge?

Accepted Answer

Chlorine ($$Cl)$$

Question 12

Which of the following best explains why noble gases are generally unreactive?

Accepted Answer

They have a stable electron configuration with a full valence shell.

Question 13

Which of the following statements about electron affinity is correct?

Accepted Answer

Electron affinity generally becomes more negative (releases more energy) across a period from left to right.

Question 14

Which of the following best describes the process of forming a cation from a transition metal atom?

Accepted Answer

The $$s$$ electrons are lost before the $$d$$ electrons when forming cations.

Question 15

Which of the following is a property of nonmetals?

Accepted Answer

They are electrical and thermal insulators.

Question 16

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

Accepted Answer

The second electron must be removed from a core shell, which is much closer to the nucleus.

Question 17

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

Accepted Answer

Potassium ($$K)$$

Question 18

Which of the following ions is diamagnetic?

Accepted Answer

$$Zn^{2+}$$ with configuration $$[Ar] 3d$$^{10}$$

Question 19

Which of the following best describes the trend in first ionization energy down a group in the periodic table?

Accepted Answer

It decreases because the valence electron is farther from the nucleus.

Question 20

Which of the following is a correct statement about the reactivity of alkali metals?

Accepted Answer

Reactivity increases down the group as ionization energy decreases.

Chapter 9: Periodic Properties of the Elements – Electron Configurations and Periodic Trends

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