Question 1

Which of the following statements best explains why isotopes of the same element have different mass numbers but similar chemical properties?

Accepted Answer

Isotopes have different numbers of neutrons, affecting their mass but not their electron configuration.

Question 2

A neutral atom of nitrogen-15 ($$^{15}\mathrm{N}) $$contains how many protons, neutrons, and electrons?

Accepted Answer

$$7$$ protons, $$8$$ neutrons, $$7$$ electrons

Question 3

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

Accepted Answer

Aufbau principle

Question 4

According to Hund's rule, how are electrons distributed in the $$2p$$ orbitals of a carbon atom ($$Z=6) in $$its ground state?

Accepted Answer

One electron is placed in each of two $$2p$$ orbitals, both with parallel spins.

Question 5

Which of the following atoms has a complete octet of valence electrons in its ground state?

Accepted Answer

Neon ($$\mathrm{Ne})$$

Question 6

A carbon atom in methane ($$\mathrm{CH}_4) $$forms four single bonds. What is the formal charge on the carbon atom?

Accepted Answer

$$0$$

Question 7

Which of the following best describes the difference between ionic and covalent bonding?

Accepted Answer

Ionic bonding involves the transfer of electrons, while covalent bonding involves sharing electrons.

Question 8

Which of the following molecules contains a polar covalent bond?

Accepted Answer

$$\mathrm{HCl}$$

Question 9

A fluorine atom in a molecule is uncharged and has one bond. How many lone pairs does it have?

Accepted Answer

Three

Question 10

Which of the following best explains why noble gases like neon ($$\mathrm{Ne}) $$are generally unreactive?

Accepted Answer

They have a full outer shell of valence electrons, achieving a stable octet.

Question 11

Which of the following is the correct electron configuration for a neutral oxygen atom ($$Z=8$$)?

Accepted Answer

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

Question 12

In a skeletal structure, how many implicit hydrogens are bonded to a carbon atom at the end of a straight line (not double or triple bonded)?

Accepted Answer

Three

Question 13

Which of the following best describes a nonpolar covalent bond?

Accepted Answer

A bond where electrons are shared equally between atoms of similar electronegativity.

Question 14

A molecule of $$\mathrm{CO}_2 ($$carbon dioxide) is nonpolar, even though it contains polar bonds. Why?

Accepted Answer

The molecule is linear, so the bond dipoles cancel each other out.

Question 15

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.

Question 16

A carbon atom with three bonds and one lone pair has what formal charge?

Accepted Answer

$$-1$$

Question 17

Which of the following best explains the appearance of red and blue regions in an electrostatic potential map of a molecule?

Accepted Answer

Red regions indicate areas of high electron density (negative potential), blue regions indicate areas of low electron density (positive potential).

Question 18

Which of the following is true about the relationship between the number of valence electrons and the column (group) of the periodic table?

Accepted Answer

Elements in the same column have the same number of valence electrons and similar reactivity.

Question 19

A positively charged nitrogen atom ($$\mathrm{N}^+) in a $$molecule is most likely to have how many bonds and lone pairs?

Accepted Answer

Four bonds, zero lone pairs

Question 20

Which of the following best describes the effect of increasing the number of protons in an atom?

Accepted Answer

It changes the atom to a different element with a new atomic number.

General Chemistry Review: Atoms, Bonding, and Organic Structure

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