$$2n^2 = 2$$ \times $$3^2 = 18$

Question 1

Which principle states that electrons fill the lowest energy sub-levels first before occupying higher energy sub-levels?

Accepted Answer

Aufbau Principle

Question 2

How many electrons can the third principal energy level (n=3) hold in total?

Accepted Answer

$$2n^2 = 2$$ 	imes $$3^2 = 18$

Question 3

Which of the following is the correct electron configuration for a neutral sodium atom (Na, Z=11)?

Accepted Answer

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

Question 4

Which sub-level can hold a maximum of 10 electrons?

Accepted Answer

d

Question 5

What is the condensed electron configuration for zinc (Zn, Z=30)?

Accepted Answer

$$[Ar]\ 4s^2$\ 3d$$^{10}$$

Question 6

Which rule explains why electrons occupy orbitals singly before pairing up within a sub-level?

Accepted Answer

Hund's Rule

Question 7

When forming a $$Ti^{2+}$$ ion from a neutral titanium atom, which electrons are removed first?

Accepted Answer

Electrons from the $$4s$$ orbital

Question 8

Which of the following elements has the electron configuration $$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^5$$?

Accepted Answer

Chlorine (Cl)

Question 9

How many orbitals are present in the $$3d$$ sub-level?

Accepted Answer

5

Question 10

Which of the following is a correct representation of the Pauli Exclusion Principle?

Accepted Answer

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

Question 11

What is the full electron configuration for a fluoride ion ($$F^-$$)?

Accepted Answer

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

Question 12

Which of the following elements has a half-filled $$3d$$ sub-level in its ground state electron configuration?

Accepted Answer

Chromium (Cr)

Question 13

What is the maximum number of electrons that can occupy the $$4f$$ sub-level?

Accepted Answer

14

Question 14

Which orbital shape is associated with the $$p$$ sub-level?

Accepted Answer

Dumbbell-shaped

Question 15

Which of the following is the correct condensed electron configuration for selenium (Se, Z=34)?

Accepted Answer

$$[Ar]\ 4s^2$\ 3d$$^{10}$$\ 4p^4$

Question 16

A neutral atom of potassium (K, Z=19) has how many valence electrons?

Accepted Answer

1

Question 17

Which of the following is the correct order of filling for the first five sub-levels according to the Aufbau Principle?

Accepted Answer

$$1s \rightarrow 2s \rightarrow 2p \rightarrow 3s \rightarrow 3p$$

Question 18

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

Accepted Answer

$$F^-$$

Question 19

How many unpaired electrons are present in a nitrogen atom ($$1s^2$$\ $$2s^2$$\ $$2p^3$$)?

Accepted Answer

3

Question 20

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

Accepted Answer

Electrons in the $$4s$$ orbital are lost before those in the $$3d$$ orbital when forming positive ions.

Electron Configuration: Principles, Rules, and Applications

Study Guide - Practice Questions