The Chemical Basis of Life: Atoms, Molecules, and Water

Comprehensive vocabulary flashcards covering atomic structure, chemical bonds, properties of water, and acid-base buffers from the lecture on the chemical basis of life.

Matter

Anything that contains mass and occupies space, existing in three physical states: solid, liquid, and gas.

Atomic Theory

The scientific principle stating that all matter is made up of atoms.

Atom

The smallest unit of matter that forms all chemical substances and cannot be further broken down into smaller pieces by chemical means.

Element

A pure substance composed of only one kind of atom, with $98$ occurring naturally in the universe.

Proton

A subatomic particle located in the nucleus of an atom that carries a positive charge ($+$).

Neutron

An uncharged, neutral subatomic particle found in the central nucleus of an atom.

Electron

A subatomic particle with a negative charge ($-$) found orbiting the nucleus within orbitals and shells.

Atomic Number

The number of protons in an atom's nucleus, which uniquely distinguishes one element from another and equals the number of electrons in a neutral atom.

Atomic Mass

A measurement indicating an atom's mass relative to other atoms, calculated primarily from the combined mass of its protons and neutrons.

Dalton

The standard unit of measurement used for atomic mass.

Mole

A unit tracking the number of atoms, defined as containing exactly Avogadro's number ($6.022 \times 10^{23}$) of particles.

Orbital

A region within an electron shell around the nucleus where there is a high probability of finding an electron, capable of holding up to $2$ electrons.

Electron Shell

A concentric energy level surrounding the nucleus that contains one or more orbitals, with each shell possessing a characteristic energy.

Valence Shell

The outermost electron shell of an atom that dictates its chemical reactivity and bonding behavior.

Valence Electrons

Electrons present in the outermost shell that are available to participate in chemical bonding with other atoms.

Isotopes

Forms of an element that contain the same number of protons but differ in their number of neutrons.

Radioisotope

An unstable isotope with excess neutrons that loses energy by spontaneously emitting radiation and/or subatomic particles.

Molecule

A chemical unit composed of two or more atoms bonded together.

Compound

Any molecule composed of two or more different elements chemically bonded together.

Molecular Formula

A chemical representation listing the element symbols and numerical subscripts to show the exact number of each atom in a molecule.

Hydrocarbon

An organic compound consisting entirely of carbon and hydrogen atoms.

Alkane

A saturated hydrocarbon consisting solely of single bonds, following the general formula $C_n H_{2n+2}$.

Alkene

An unsaturated hydrocarbon containing at least one carbon-carbon double bond, following the general formula $C_n H_{2n}$.

Alkyne

An unsaturated hydrocarbon containing at least one carbon-carbon triple bond, following the general formula $C_n H_{2n-2}$.

Octet Rule

The principle that atoms are most stable when their outermost valence shell is filled with $8$ electrons ($2$ electrons for the first shell).

Covalent Bond

A strong chemical bond formed when two atoms share one or more pairs of electrons.

Electronegativity

An atom's attractive power or affinity for the shared electrons within a covalent bond.

Polar Covalent Bond

A covalent bond formed between atoms of differing electronegativity, leading to unequal electron sharing and partial electric charges across the molecule.

Nonpolar Covalent Bond

A covalent bond formed between atoms with similar electronegativities, resulting in equal sharing of electrons and no net charge difference.

Ion

An atom or molecule that carries an electric charge due to the loss or gain of one or more electrons.

Cation

A positively charged ion formed when an atom loses one or more electrons.

Anion

A negatively charged ion formed when an atom gains one or more electrons.

Ionic Bond

A chemical bond resulting from the electrostatic attraction between an oppositely charged cation and anion.

Hydrogen Bond

A weak electrostatic attraction between a partially positive hydrogen atom in a polar molecule and an electronegative atom in another polar molecule.

Chemical Reaction

A process in which one or more substances (reactants) are converted into different substances (products) through the formation or breaking of chemical bonds.

Hydrophilic

"Water-loving"; describes polar or ionic substances that readily dissolve in water.

Hydrophobic

"Water-fearing"; describes nonpolar molecules (such as oils and hydrocarbons) that do not dissolve in water.

Amphipathic

"Both loves"; describes molecules containing both hydrophilic (polar/ionized) and hydrophobic (nonpolar) regions.

Micelle

A spherical aggregate formed by amphipathic molecules in water, with polar regions facing the external aqueous environment and nonpolar regions sheltered inside.

Heat of Vaporization

The heat energy required to transform a liquid substance into a gas at its boiling point.

Heat of Fusion

The heat energy that must be withdrawn from a liquid to solidify it, or released to melt a solid into a liquid.

Specific Heat

The amount of heat energy required to raise the temperature of a substance by $1\,^{\circ}\text{C}$.

pH

Potential of Hydrogen; a logarithmic scale from $0$ to $14$ indicating the concentration of hydrogen ions ($H^+$) in an aqueous solution.

Acid

A substance that dissociates in water to release hydrogen ions ($H^+$), lowering the pH below $7$.

Base

An alkaline substance that binds hydrogen ions ($H^+$) or releases hydroxide ions ($OH^-$) in water, raising the pH above $7$.

Buffer

An acid-base system that acts as an $H^+$ sponge, absorbing or releasing hydrogen ions to minimize changes in pH.