Question 1

Which principle states that electrons will fill the lowest available energy orbital first when building up the electron configuration of an atom?

Accepted Answer

Aufbau Principle

Question 2

According to the Pauli Exclusion Principle, what is the maximum number of electrons that can occupy a single orbital, and what must be true about their spins?

Accepted Answer

Two electrons, with opposite spins

Question 3

How many electrons can be held in the $$n=2$$ energy level of an atom?

Accepted Answer

$$8$$

Question 4

Which electron configuration represents a magnesium atom ($$12$$ electrons) in its ground state?

Accepted Answer

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

Question 5

Which of the following ions is isoelectronic with neon ($$Ne$$, $$Z=10$$)?

Accepted Answer

$$Na^+$$

Question 6

If an atom has the electron configuration $$1s^2$$\ $$2s^2$$\ $$2p^3$$, what element is it?

Accepted Answer

Nitrogen ($$N)$$

Question 7

Which rule requires that electrons must occupy degenerate orbitals singly before pairing up?

Accepted Answer

Hund's Rule

Question 8

How many orbitals are present in the $$2p$$ sublevel, and how many electrons can it hold?

Accepted Answer

Three orbitals, six electrons

Question 9

Which of the following electron configurations violates the Pauli Exclusion Principle?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^7$$

Question 10

A neutral atom of boron ($$B) $$has $$5$$ electrons. What is its electron configuration?

Accepted Answer

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

Question 11

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

Accepted Answer

Neon ($$Ne)$$

Question 12

What is the maximum number of electrons that can occupy the $$3d$$ sublevel?

Accepted Answer

$$10$$

Question 13

Which of the following statements about electron configurations is correct?

Accepted Answer

Electrons fill orbitals of equal energy singly before pairing

Question 14

Which of the following ions is isoelectronic with argon ($$Ar$$, $$Z=18$$)?

Accepted Answer

$$K^+$$

Question 15

If an atom has the electron configuration $$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^1$$, what element is it?

Accepted Answer

Sodium ($$Na)$$

Question 16

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

Accepted Answer

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

Question 17

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

Accepted Answer

Phosphorus ($$P)$$

Question 18

How many electrons are present in a neutral arsenic ($$As) $$atom?

Accepted Answer

$$33$$

Question 19

Which of the following is the correct abbreviated electron configuration for calcium ($$Ca$$, $$Z=20$$)?

Accepted Answer

$$[Ar]\ 4s^2$

Question 20

Which of the following statements about the stability of electron configurations is true?

Accepted Answer

Half-filled and fully-filled sublevels are more stable than partially filled ones

Electron Configurations and Periodic Table Trends: Study Notes

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