Q: What is the effective nuclear charge ($$Z_{\text{eff}}) $$experienced by a 3p electron in phosphorus (P, atomic number 15)? Use $$Z_{\text{eff}} = Z - S$$, where $$S is $$the number of core electrons.

$$Z_{\text{eff}} = 15 - 10 = 5$$

Question 1

Which of the following correctly describes Hund’s Rule as it applies to the orbital diagrams of boron and carbon?

Accepted Answer

Electrons fill each orbital in a sublevel singly before any orbital gets a second electron.

Question 2

What is the electron configuration for the Fe$$^{3+}$$ ion?

Accepted Answer

$$1s^22s^22$p^63s^23$p^63d^5$

Question 3

Which of the following elements has the highest first ionization energy?

Accepted Answer

Neon (Ne)

Question 4

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

Accepted Answer

Cl$$^-$$

Question 5

What is the effective nuclear charge ($$Z_{	ext{eff}}) $$experienced by a 3p electron in phosphorus (P, atomic number 15)? Use $$Z_{	ext{eff}} = Z - S$$, where $$S is $$the number of core electrons.

Accepted Answer

$$Z_{	ext{eff}} = 15 - 10 = 5$$

Question 6

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

Accepted Answer

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

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 represents a diamagnetic species?

Accepted Answer

$$1s^22s^22$p^63s^23$p^6$$

Question 9

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 because valence electrons are farther from the nucleus.

Question 10

Which of the following is the correct electron configuration for the ground state of chromium (Cr)?

Accepted Answer

$$[Ar]4s^13$d^5$

Question 11

Which of the following statements about the formation of cations from transition metals is correct?

Accepted Answer

Electrons are removed from the highest principal energy level (ns) before the (n-1)d sublevel.

Question 12

Which of the following ions has the largest ionic radius?

Accepted Answer

F$$^-$$

Question 13

Which of the following best explains why halogens are strong oxidizing agents?

Accepted Answer

They have high electron affinities and readily gain electrons.

Question 14

Which of the following is the correct noble gas electron configuration for bromide ion (Br$$^-$$)?

Accepted Answer

$$[Kr]$$

Question 15

Which of the following best describes the trend in electron affinity across a period from left to right?

Accepted Answer

Electron affinity becomes more negative.

Question 16

Which of the following quantum number sets is NOT allowed for an electron in an atom?

Accepted Answer

$$n=2,\ l=2,\ m_l=0,\ m_s=+\frac{1}{2}$$

Question 17

Which of the following elements is expected to have the smallest atomic radius?

Accepted Answer

Argon (Ar)

Question 18

Which of the following best explains why cations are smaller than their parent atoms?

Accepted Answer

Cations have fewer electrons, resulting in a higher effective nuclear charge per electron.

Question 19

Which of the following is the correct electron configuration for the Al$$^{3+}$$ ion?

Accepted Answer

$$1s^22s^22$p^6$$

Question 20

Which of the following best describes the trend in metallic character as you move from left to right across a period?

Accepted Answer

Metallic character decreases.

Chapter 8: Electron Configurations and Periodic Trends – Study Notes

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