Q: Which of the following best explains why atomic radii decrease across a period from left to right in the periodic table?

The effective nuclear charge ($$Z_{\text{eff}}) $$increases, pulling electrons closer to the nucleus.

Q: According to Slater’s rules, what is the effective nuclear charge ($$Z_{\text{eff}}) $$experienced by the 3p electrons in sulfur ($$\mathrm{S}$$, atomic number 16)?

$$Z_{\text{eff}} = 16 - 10.55 = 5.45$$

Question 1

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

Accepted Answer

The effective nuclear charge ($$Z_{	ext{eff}}) $$increases, pulling electrons closer to the nucleus.

Question 2

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

Accepted Answer

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

Question 3

What is the condensed electron configuration for calcium ($$\mathrm{Ca}$$, atomic number 20)?

Accepted Answer

$$[\mathrm{Ar}]\,4s^2$

Question 4

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

Accepted Answer

$$\mathrm{Na}^+$$

Question 5

According to Slater’s rules, what is the effective nuclear charge ($$Z_{	ext{eff}}) $$experienced by the 3p electrons in sulfur ($$\mathrm{S}$$, atomic number 16)?

Accepted Answer

$$Z_{	ext{eff}} = 16 - 10.55 = 5.45$$

Question 6

Which of the following statements about the Pauli Exclusion Principle is correct?

Accepted Answer

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

Question 7

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

Accepted Answer

Ionization energy decreases due to increasing atomic radius and electron shielding.

Question 8

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

Accepted Answer

Magnesium ($$\mathrm{Mg})$$

Question 9

What is the electron configuration for the $$\mathrm{Mn}^{2+}$$ ion?

Accepted Answer

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

Question 10

Which of the following best explains why the second ionization energy ($$IE_2) of $$sodium is much higher than its first ionization energy ($$IE_1$$)?

Accepted Answer

The second electron is removed from a filled shell, which is closer to the nucleus and more tightly bound.

Question 11

Which of the following elements has the most negative electron affinity?

Accepted Answer

Chlorine ($$\mathrm{Cl})$$

Question 12

Which of the following is a property of metals?

Accepted Answer

Good conductors of heat and electricity

Question 13

Which of the following ions has the smallest ionic radius in the isoelectronic series $$\mathrm{O}^{2-}$$, $$\mathrm{F}^-$$, $$\mathrm{Na}^+$$, $$\mathrm{Mg}^{2+}$$, $$\mathrm{Al}^{3+}$$?

Accepted Answer

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

Question 14

Which quantum number is associated with the orientation of an orbital in space?

Accepted Answer

Magnetic quantum number ($$m_l)$$

Question 15

Which of the following best describes Hund’s rule?

Accepted Answer

Electrons occupy degenerate orbitals singly before pairing up.

Question 16

Which of the following statements about transition metals is correct?

Accepted Answer

Their d orbitals fill with principal quantum number $$n-1$$ relative to their period.

Question 17

Which of the following elements is a metalloid?

Accepted Answer

Silicon ($$\mathrm{Si})$$

Question 18

Which of the following best explains why noble gases have positive electron affinities?

Accepted Answer

Adding an electron requires placing it in a new, higher energy shell.

Question 19

Which of the following is the correct order of increasing atomic radius?

Accepted Answer

$$\mathrm{F} \u003c \mathrm{N} \u003c \mathrm{O}$$

Question 20

Which of the following best describes the trend in metallic character across a period?

Accepted Answer

Metallic character decreases from left to right.

Chapter 3: Periodic Properties of the Elements – Study Guide

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