Question 1

Which set of quantum numbers is NOT allowed for an electron in an atom?

Accepted Answer

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

Question 2

How many electrons can occupy all of the orbitals in the $$n=3$$ shell of an atom?

Accepted Answer

18

Question 3

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

Accepted Answer

$$\mathrm{K}^+$$

Question 4

Which statement best explains why the $$4s$$ orbital is filled before the $$3d$$ orbital in the ground state electron configuration of potassium ($$\mathrm{K}$$)?

Accepted Answer

The $$4s$$ orbital is lower in energy than the $$3d$$ orbital.

Question 5

A certain element has the electron configuration $$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^1. $$What is the charge and electron configuration of its most common ion?

Accepted Answer

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

Question 6

Which of the following best describes a paramagnetic atom?

Accepted Answer

An atom with one or more unpaired electrons.

Question 7

How many different values of $$m_l$$ are possible for an electron in a $$d$$ orbital?

Accepted Answer

5

Question 8

Which of the following ions has the same electron configuration as neon ($$\mathrm{Ne}$$)?

Accepted Answer

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

Question 9

A transition metal ion has the electron configuration $$[\mathrm{Ar}]\ 3d^5$. Which ion is it?

Accepted Answer

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

Question 10

Which of the following statements about the Pauli exclusion principle is correct?

Accepted Answer

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

Question 11

Which of the following electron configurations represents an atom in an excited state?

Accepted Answer

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

Question 12

How many orbitals are present in the $$n=4$$ shell?

Accepted Answer

16

Question 13

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

Accepted Answer

They have completely filled valence shells, making them electronically stable.

Question 14

A sample of magnesium is exposed to a strong magnetic field and is found to be weakly repelled. What does this indicate about its electron configuration?

Accepted Answer

All electrons are paired, so magnesium is diamagnetic.

Question 15

Which of the following ions is isoelectronic with $$\mathrm{Kr}$$?

Accepted Answer

$$\mathrm{Sn}^{4+}$$

Question 16

Which quantum number determines the shape of an atomic orbital?

Accepted Answer

Angular momentum quantum number ($$l)$$

Question 17

Which of the following correctly describes Hund’s rule?

Accepted Answer

Electrons occupy degenerate orbitals singly before pairing up.

Question 18

A lead(IV) ion ($$\mathrm{Pb}^{4+}) $$has which electron configuration?

Accepted Answer

$$[\mathrm{Xe}]\ 4f$$^{14}$$\ 5d$$^{10}$$

Question 19

Which of the following best describes the electron configuration of a $$\mathrm{C}^{4-}$$ ion?

Accepted Answer

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

Question 20

Which of the following statements about transition metal ions is correct?

Accepted Answer

They usually lose the valence $$s$$ electrons before the $$d$$ electrons when forming cations.

Quantum Numbers, Atomic Orbitals, and Electron Configurations

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