AP BIOLOGY

Detailed explanation-1: -A single hydrogen atom can participate in two hydrogen bonds, rather than one.

Detailed explanation-2: -It’s called the HONC rule, or sometimes known as HONC 1234 rule. The number refers to the number of bonds each of the element makes: Hydrogen makes 1 bond, Oxygen makes 2 bonds, Nitrogen makes 3 bonds and Carbon makes 4 bonds.

Detailed explanation-3: -The hydrogen atom and the halogen atoms form only one covalent bond to other atoms in stable neutral compounds. However, the carbon, oxygen, and nitrogen atoms can bond to more than one atom.

Detailed explanation-4: -Adenine pairs with thymine with 2 hydrogen bonds. Guanine pairs with cytosine with 3 hydrogen bonds. This creates a difference in strength between the two sets of Watson and Crick bases. Guanine and cytosine bonded base pairs are stronger then thymine and adenine bonded base pairs in DNA.

Detailed explanation-5: -To achieve stability, carbon must find four more electrons to fill its outer shell, giving a total of eight and satisfying the octet rule. Carbon atoms may thus form bonds to as many as four other atoms.