Question 1

Which statement best describes the Pauli Exclusion Principle?

Accepted Answer

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

Question 2

What is the correct electron configuration for a neutral oxygen atom?

Accepted Answer

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

Question 3

How many unpaired electrons are present in a ground-state carbon atom?

Accepted Answer

2

Question 4

Which of the following elements is paramagnetic in its ground state?

Accepted Answer

Oxygen ($$O)$$

Question 5

What is the abbreviated electron configuration for bromine ($$Br$$)?

Accepted Answer

$$[Ar] 4s^2$ 3d$$^{10}$$ 4p^5$

Question 6

According to Hund's Rule, which of the following is true for the ground-state electron configuration of nitrogen ($$N$$)?

Accepted Answer

Each of the three $$2p$$ orbitals contains one electron, all with parallel spins.

Question 7

How many valence electrons does sulfur ($$S) $$have?

Accepted Answer

6

Question 8

Which quantum number is responsible for distinguishing the two electrons in a single orbital?

Accepted Answer

Spin quantum number $$m_s$$

Question 9

A sample of chlorine gas is exposed to a strong magnetic field. What is observed and why?

Accepted Answer

It is weakly attracted to the field because it has one unpaired electron (paramagnetic).

Question 10

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

Accepted Answer

They have completely filled $$s$$ and $$p$$ sublevels in their outermost shell.

Question 11

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

Accepted Answer

6

Question 12

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

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^5$$ with three electrons in the same $$2p$$ orbital with the same spin

Question 13

Which of the following statements about electron orbitals is correct?

Accepted Answer

An orbital is a region of space with a high probability of finding an electron.

Question 14

A sodium atom ($$Na) $$loses one electron to form $$Na^+. $$What is the electron configuration of $$Na^+$$?

Accepted Answer

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

Question 15

Which of the following best describes wave-particle duality as it applies to electrons?

Accepted Answer

Electrons exhibit both wave-like and particle-like properties.

Question 16

How many unpaired electrons are present in a ground-state chlorine atom?

Accepted Answer

1

Question 17

Which of the following is the correct order of filling for the first four principal energy levels according to the Aufbau principle?

Accepted Answer

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

Question 18

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

Accepted Answer

$$Fe^{3+}$$

Question 19

Which of the following statements about quantum numbers is correct?

Accepted Answer

The spin quantum number $$m_s$$ can have values of $$+\frac{1}{2} or$$ $$-\frac{1}{2}.$$

Question 20

Which of the following 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 for neutral atoms.

Electron Configurations and Quantum Theory: Study Notes

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