Question 1

Which of the following correctly describes the order in which electron orbitals are filled according to the Aufbau principle?

Accepted Answer

$$1s \rightarrow 2s \rightarrow 2p \rightarrow 3s \rightarrow 3p \rightarrow 4s \rightarrow 3d$$

Question 2

Which quantum number primarily determines the energy level of an electron in an atom?

Accepted Answer

The principal quantum number ($$n)$$

Question 3

What is the electron configuration for beryllium (atomic number 4)?

Accepted Answer

$$1s^2$$ $$2s^2$$

Question 4

Which of the following statements best explains why the $$4s$$ orbital is filled before the $$3d$$ orbital?

Accepted Answer

The $$4s$$ orbital is lower in energy than the $$3d$$ orbital when empty or partially filled.

Question 5

How many electrons can the $$p$$ subshell hold in total?

Accepted Answer

6

Question 6

Which of the following is the correct electron configuration for sodium (atomic number 11)?

Accepted Answer

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

Question 7

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

Accepted Answer

Hund's Rule

Question 8

What is the maximum number of electrons that can occupy the $$n=3$$ energy level?

Accepted Answer

18

Question 9

Which of the following elements has the electron configuration $$1s^2$$ $$2s^2$$ $$2p^2$$?

Accepted Answer

Carbon

Question 10

A neutral atom has the electron configuration $$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^2$$ $$3p^4. $$What is the element?

Accepted Answer

Sulfur

Question 11

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

Accepted Answer

Pauli Exclusion Principle

Question 12

How many electrons are in the $$3d$$ subshell of a zinc atom ($$Z=30) in $$its ground state?

Accepted Answer

10

Question 13

Which of the following best describes the meaning of 'degenerate orbitals'?

Accepted Answer

Orbitals with the same energy within a given subshell

Question 14

Which of the following is the correct electron configuration for an oxygen atom?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^4$$

Question 15

A hospital uses argon gas in its lighting systems. What is the electron configuration for argon ($$Z=18$$)?

Accepted Answer

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

Question 16

Which of the following quantum numbers describes the orientation of an orbital in space?

Accepted Answer

Magnetic quantum number ($$m_l)$$

Question 17

Which of the following is a valid set of quantum numbers for an electron in a $$3p$$ orbital?

Accepted Answer

$$n=3,\ l=1,\ m_l=0,\ m_s=+\frac{1}{2}$$

Question 18

A transition metal ion is found to have the electron configuration $$[Ar] 3d^5$. Which ion is this most likely to be?

Accepted Answer

Fe$$^{3+}$$

Question 19

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

Accepted Answer

They have completely filled valence shells.

Question 20

Which of the following elements has a partially filled $$2p$$ subshell in its ground state?

Accepted Answer

Nitrogen

Electron Configurations and Quantum States

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