APCE Chemical Bonding & Molecular Structure

Question 1

What type of bond is formed when two atoms share electrons?

Accepted Answer

Covalent bond.

Answer

A covalent bond is formed when two atoms share one or more pairs of electrons to achieve a more stable electron configuration, typically an octet. This sharing occurs between nonmetal atoms and results in the formation of molecules. The shared electrons are attracted to the nuclei of both atoms, holding them together.

Question 2

What is the octet rule?

Accepted Answer

Atoms tend to have 8 electrons in their valence shell.

Answer

The octet rule states that atoms tend to gain, lose, or share electrons in order to achieve a stable electron configuration with eight electrons in their outermost (valence) shell. This configuration, similar to that of noble gases, is energetically favorable and drives much of chemical bonding. While there are exceptions, it's a fundamental principle for many main group elements.

Question 3

What is the main characteristic of ionic bonding?

Accepted Answer

One atom donates electrons to another atom, forming oppositely charged ions.

Answer

Ionic bonding involves the complete transfer of one or more valence electrons from a metal atom to a nonmetal atom. This transfer results in the formation of positively charged cations and negatively charged anions, which are then held together by strong electrostatic forces of attraction. The large electronegativity difference between the atoms facilitates this electron transfer.

Question 4

What is the bond angle in a molecule with a tetrahedral geometry?

Accepted Answer

109.5°.

Answer

In a molecule with tetrahedral geometry, such as methane (CH₄), a central atom is bonded to four other atoms with no lone pairs. The electron domains repel each other equally, arranging themselves in three dimensions to maximize separation. This specific arrangement results in bond angles of approximately 109.5 degrees between any two bonds.

Question 5

Which of the following molecules has a polar covalent bond?

Accepted Answer

H₂O.

Answer

A polar covalent bond forms when there is an unequal sharing of electrons between two atoms due to a difference in their electronegativities. In H₂O, oxygen is significantly more electronegative than hydrogen, pulling the shared electrons closer to itself. This creates partial negative charges on oxygen and partial positive charges on hydrogen, making the O-H bonds polar.

AP Practice Test

AP Practice Test

APCE Chemical Bonding & Molecular Structure