Chapter 2: Chemical Context of Life Flashcards

Vocabulary flashcards covering the basic biological chemistry concepts from Chapter 2, including essential elements, atomic structure, electron energy levels, types of chemical bonds, and chemical reactions.

Essential Elements

The 25 out of 92 natural elements required for life, with carbon (C), oxygen (O), hydrogen (H), and nitrogen (N) making up 96% of living matter.

Trace Elements

Elements required by an organism in minute quantities (less than 0.01% of body mass), which are still essential elements even though they are only needed in small amounts.

Atom

The basic unit of matter consisting of subatomic particles: uncharged neutrons and positively charged protons in the nucleus, and negatively charged electrons in a cloud around the nucleus.

Neutrons

Uncharged subatomic particles located inside the atomic nucleus.

Protons

Positively charged subatomic particles located inside the atomic nucleus.

Electrons

Negatively charged subatomic particles located in a cloud around the atomic nucleus.

Valence Electrons

Electrons located in the outermost shell (valence shell) of an atom that determine its chemical reactivity.

Valence Shell

The outermost electron shell of an atom; a completed valence shell makes an atom unreactive or inert.

Chemical Bonds

Attractions that hold atoms close together when they share or transfer valence electrons.

Covalent Bond

A strong chemical bond formed when two atoms share valence electrons to complete their valence shells.

Molecule

Two or more atoms held together by covalent bonds.

Single Covalent Bond

A bond formed by the sharing of one pair of valence electrons.

Double Covalent Bond

A bond formed by the sharing of two pairs of valence electrons.

Structural Formula

A notation used to represent atoms and bonding, where a line represents a covalent bond (e.g., $H-H$).

Molecular Formula

An abbreviated representation indicating the literal composition of a molecule (e.g., $H_2$).

Electronegativity

The measure of an atom's ability to pull shared electrons toward itself within a covalent bond.

Nonpolar Covalent Bond

A covalent bond where electrons are shared equally between two atoms of similar electronegativity, such as the bond in $O_2$.

Polar Covalent Bond

A covalent bond where one atom is more electronegative than the other, causing unequal electron sharing and partial positive ($\delta+$) or negative ($\delta-$) charges.

Ion

A charged atom or molecule resulting from the complete transfer of one or more electrons.

Cation

A positively charged ion.

Anion

A negatively charged ion.

Ionic Bond

A chemical bond resulting from the attraction between an anion and a cation after an electron transfer.

Salts

Compounds formed by ionic bonds, often forming crystals, which do not always exist in a 1:1 atomic ratio (e.g., $MgCl_2$).

Hydrogen Bond

A weak bond formed when a hydrogen atom covalently bonded to an electronegative atom is also attracted to another electronegative atom (usually oxygen or nitrogen).

Van der Waals Interactions

Weak attractions resulting from asymmetrical electron distribution that creates temporary local partial positive or negative charges ("hot spots").

Reactants

The starting materials in a chemical reaction.

Products

The resulting materials produced by a chemical reaction.

Chemical Equilibrium

The state reached in a reversible reaction when the forward and reverse reaction rates are equal.