Lecture 2: Chemistry of Life (BIO 111)

Vocabulary flashcards covering key concepts from atoms, bonds, and water properties in BIO 111 Lecture 2.

Atom

The smallest functional unit of matter; the basic unit of an element.

Element

A substance consisting of atoms with a specific number of protons; cannot be broken down into simpler substances by chemical means.

Molecule

Two or more atoms joined together via chemical bonds.

Compound

A substance whose molecules contain two or more different elements.

Proton

Positively charged subatomic particle located in the nucleus.

Neutron

Electrically neutral subatomic particle located in the nucleus.

Electron

Negatively charged subatomic particle orbiting the nucleus.

Atomic number

Number of protons in the nucleus; defines the element.

Mass number

Sum of protons and neutrons in the nucleus; used to describe isotopes.

Isotope

Forms of an element with different numbers of neutrons but the same number of protons.

Atomic mass

Average mass of naturally occurring isotopes, weighted by their abundance.

Electron shell

Discrete energy levels around the nucleus that hold electrons; each shell can hold a limited number of electrons.

Orbital

A region within an electron shell where an electron is likely to be found; each orbital holds up to 2 electrons.

Valence electrons

Electrons in the outermost electron shell; determine bonding behavior.

Octet rule

Atoms are most stable when their valence shell is full (eight electrons in the main group).

Periodic table

Table organized into periods (rows) and groups (columns) showing element properties.

Period

Horizontal row in the periodic table; corresponds to the number of electron shells.

Group

Vertical column in the periodic table; corresponds to the number of electrons in the outermost shell.

Electronegativity

Atom's ability to attract bonding electrons in a bond.

Covalent bond

Bond formed when atoms share electrons; can be polar or nonpolar depending on electronegativity differences.

Polar covalent bond

Covalent bond with unequal sharing of electrons due to different electronegativities; creates partial charges.

Nonpolar covalent bond

Covalent bond with equal sharing of electrons when electronegativities are similar.

Ionic bond

Bond formed by transfer of electrons; attraction between oppositely charged ions (cation and anion).

Cation

Ion with a positive charge.

Anion

Ion with a negative charge.

Hydrogen bond

Weak bond between a hydrogen attached to a more electronegative atom and another electronegative atom; important for macromolecule structure.

Van der Waals interactions

Very weak, transient interactions from momentary charge imbalances; can be significant when many occur together.

Water

H2O; a polar molecule that is an excellent solvent and forms hydrogen bonds; essential for life.

Hydrophilic

Molecules that interact well with water (polar or charged) and dissolve readily.

Hydrophobic

Molecules that do not interact well with water (nonpolar) and tend to avoid water.

Cohesion

Attraction between like molecules (e.g., water molecules sticking to each other).

Adhesion

Attraction between different substances (e.g., water to a surface).

Surface tension

The energy required to increase the surface area of a liquid; due to cohesive forces at the surface.

Ice vs liquid water density

Water is denser as a liquid than as ice; ice floats on water.

Specific heat

Energy required to raise the temperature of 1 g of a substance by 1°C.

Heat of vaporization

Energy required to convert 1 g of liquid to gas.

Water polarity

Water is a polar molecule due to its bent shape and polar covalent bonds.

Macromolecule

A large molecule such as carbohydrates, proteins, lipids, or nucleic acids.

Electron configuration

Arrangement of electrons in shells and subshells (e.g., 1s2 2s2 2p6 for neon).

Nucleus

Central core of the atom containing protons and neutrons; electrons orbit around it.