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

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

Accepted Answer

$\mathrm{Cl^-}$

Question 3

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

Accepted Answer

$18$

Question 4

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 5

Which principle explains why electrons fill the lowest available energy orbitals first?

Accepted Answer

Aufbau Principle

Question 6

How many unpaired electrons are present in a ground-state atom of nitrogen ($Z=7$)?

Accepted Answer

$3$

Question 7

Which of the following statements about the $3d$ subshell is correct?

Accepted Answer

It contains 5 orbitals and can hold up to 10 electrons.

Question 8

Which of the following ions has the electron configuration $[\mathrm{Ne}]\ 3s^2\ 3p^6$?

Accepted Answer

$\mathrm{Cl^-}$

Question 9

A certain element has the electron configuration $[\mathrm{Ar}]\ 4s^2\ 3d^{10}\ 4p^2$. What is the identity of this element?

Accepted Answer

$\mathrm{Ge}$

Question 10

Which of the following best describes a paramagnetic substance?

Accepted Answer

A substance with unpaired electrons that is weakly attracted to a magnetic field

Question 11

What is the maximum number of electrons that can have the quantum numbers $n=4$ and $l=2$ in a single atom?

Accepted Answer

$10$

Question 12

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

Accepted Answer

$\mathrm{F^-}$

Question 13

Which quantum number determines the shape of an atomic orbital?

Accepted Answer

Angular momentum quantum number ($l$)

Question 14

A transition metal ion has the configuration $[\mathrm{Ar}]\ 3d^5$. What is the most likely identity of this ion?

Accepted Answer

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

Question 15

Which of the following best explains why noble gases do not tend to form ions?

Accepted Answer

They have a filled outermost shell, making them electronically stable.

Question 16

Which of the following electron configurations represents a $\mathrm{Mg^{2+}}$ ion?

Accepted Answer

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

Question 17

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

Accepted Answer

$16$

Question 18

Which rule states that electrons will fill degenerate orbitals singly before pairing up?

Accepted Answer

Hund's Rule

Question 19

Which of the following ions has a pseudo-noble gas configuration?

Accepted Answer

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

Question 20

Which of the following best describes the Pauli Exclusion Principle?

Accepted Answer

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

Quantum Numbers, Atomic Orbitals, and Electron Configurations

Study Guide - Practice Questions