Question 1

Which principle states that no two electrons in an atom can have the same four quantum numbers?

Accepted Answer

Pauli Exclusion Principle

Question 2

What is the correct electron configuration for a neutral phosphorus (P) atom?

Accepted Answer

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

Question 3

According to Hund's Rule, how are electrons distributed in degenerate (equal energy) orbitals?

Accepted Answer

Electrons fill all orbitals singly with parallel spins before pairing.

Question 4

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

Accepted Answer

Br

Question 5

What is the electron configuration of the Fe$$^{2+}$$ ion?

Accepted Answer

$$[Ar] 3d^6$

Question 6

Which of the following ions has the largest ionic radius?

Accepted Answer

$$\mathrm{S}^{2-}$$

Question 7

Which of the following best explains why the second electron affinity of oxygen is positive?

Accepted Answer

There is strong electron-electron repulsion when adding an electron to a negatively charged ion.

Question 8

Which of the following correctly describes the trend in atomic radius across a period from left to right?

Accepted Answer

Atomic radius decreases due to increased nuclear charge.

Question 9

Which element has the electron configuration $$[Ar] 4s^1$ 3d$$^{10}$$?

Accepted Answer

Cu

Question 10

A neutral atom of which element has the greatest number of unpaired electrons in its ground state?

Accepted Answer

Nitrogen

Question 11

Which of the following statements about the periodic trend of ionization energy is correct?

Accepted Answer

Ionization energy increases across a period and decreases down a group.

Question 12

Which of the following is the correct order of increasing size for the species: $$\mathrm{K}^+$$, $$\mathrm{Cl}^-$$, $$\mathrm{S}^{2-}$$, $$\mathrm{Ca}^{2+}$$?

Accepted Answer

$$\mathrm{Ca}^{2+} \u003c \mathrm{K}^+ \u003c \mathrm{Cl}^- \u003c \mathrm{S}^{2-}$$

Question 13

Which of the following best describes the electron configuration of a chromium atom (Cr)?

Accepted Answer

$$[Ar] 4s^1$ 3d^5$

Question 14

Which of the following is the correct electron-in-box diagram for the ground state of carbon?

Accepted Answer

Two boxes for 2p, each with one upward arrow

Question 15

Which of the following statements about electron affinity is correct?

Accepted Answer

Electron affinity becomes more negative across a period.

Question 16

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

Accepted Answer

Cations have fewer electrons, reducing electron-electron repulsion and increasing effective nuclear charge.

Question 17

Which of the following elements is most likely to form an anion with a $$2-$$ charge?

Accepted Answer

Oxygen

Question 18

Which block of the periodic table contains the lanthanide series?

Accepted Answer

f block

Question 19

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

Accepted Answer

Metallic character decreases across a period.

Electronic Configurations and Periodic Trends: Study Notes for General Chemistry

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