Chapter 2: The Chemical Foundation of Life

Vocabulary flashcards covering core concepts of Chapter 2: The Chemical Foundation of Life, including atomic structure, isotopes, chemical bonding, properties of water, and pH.

Matter

Anything that occupies space and has mass.

Element

A unique substance with specific chemical and physical properties that cannot be broken down into simpler substances by ordinary chemical reactions.

Four Most Common Elements of Life

Carbon (C), Hydrogen (H), Oxygen (O), and Nitrogen (N), which together compose $96\%$ of living matter.

Atom

The smallest unit of matter that retains all the chemical properties of an element.

Atomic Nucleus

The central region of an atom that contains protons and neutrons.

Proton

A positively charged sub-atomic particle located in the nucleus with a charge of $+1$ and a mass of $1\,amu$.

Neutron

An uncharged sub-atomic particle located in the nucleus with a charge of $0$ and a mass of $1\,amu$.

Electron

A negatively charged sub-atomic particle located in orbitals surrounding the nucleus with a charge of $-1$ and a mass of $0\,amu$.

Atomic Number

The distinct number of protons in the nucleus of an atom that uniquely identifies a specific element.

Atomic Mass

The total mass of an atom expressed in atomic mass units (amu), roughly equal to the sum of its protons and neutrons.

Isotopes

Different forms of the same element that have the same number of protons but a different number of neutrons.

Hydrogen Isotopes

The three isotope forms of hydrogen: Protium ($^1\text{H}$ with $0$ neutrons), Deuterium ($^2\text{H}$ with $1$ neutron), and Tritium ($^3\text{H}$ with $2$ neutrons).

Radioisotopes

Unstable isotopes that undergo natural radioactive decay by emitting neutrons, protons, and electrons.

Radiometric Dating

A research technique that determines the age of fossils or organic matter by measuring the decay of radioisotopes (e.g., Carbon-14 decaying to Nitrogen-14 over time).

Bohr Model

An early atomic model showing a central nucleus containing protons and neutrons, surrounded by electrons in circular energy shells at specific distance levels.

Valence Shell

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

Octet Rule

The principle stating that atoms achieve their most stable configuration when their outer energy levels (such as the $2n$ or $3n$ shells) contain $8$ electrons.

Reactants

The starting substances present and consumed at the beginning of a chemical reaction.

Products

The final substances produced at the end of a chemical reaction.

Molecule

A group of two or more atoms bound together specifically by covalent chemical bonds.

Compound

A substance composed of two or more different kinds of atoms bonded together in fixed proportions.

Covalent Bond

An attractive force formed between atoms through the sharing of valence electrons.

Polar Covalent Bond

A covalent bond where electrons are shared unequally between atoms due to differences in electronegativity, creating partial positive ($\delta+$) and partial negative ($\delta-$) charges.

Non-Polar Covalent Bond

A covalent bond in which valence electrons are shared equally between atoms.

Ionic Bond

A chemical bond formed by the electrostatic attraction between oppositely charged ions created when one atom transfers electrons to another.

Ion

An atom or group of atoms carrying a net positive or negative electric charge due to gaining or losing one or more electrons.

Hydrogen Bond

A weak interaction between a hydrogen atom carrying a partial positive charge ($\delta+$) and an electronegative atom carrying a partial negative charge ($\delta-$) on an adjacent molecule.

Specific Heat

The amount of heat energy a substance must absorb or lose to change its temperature by a given amount.

Heat of Vaporization

The amount of heat energy required to transition a liquid into a gas.

Evaporative Cooling

The reduction in surface temperature of a liquid as higher-energy molecules convert into gas and escape.

Sphere of Hydration

A cluster of water molecules surrounding an individual charged ion (such as $\text{Na}^+$ or $\text{Cl}^-$) when a salt dissolves in water.

Solvent

A liquid substance capable of dissolving other compounds (solutes).

Solute

A substance dissolved within a liquid solvent.

Cohesion

The intermolecular force of attraction between like molecules, such as water molecules forming hydrogen bonds with each other.

Adhesion

The attraction between unlike molecules, such as water molecules adhering to glass or cell walls.

Surface Tension

The capacity of a liquid surface to resist external force due to enhanced cohesive hydrogen bonding among surface molecules.

Capillary Action

The movement of water up narrow tubes against gravity caused by adhesive forces to the tube walls exceeding cohesive forces between water molecules.

pH

A measure of hydrogen ion concentration in a solution, calculated using the formula $\text{pH} = -\log_{10}([\text{H}^+])$.

Acidic Solution

A solution characterized by a high concentration of hydrogen ions ($\text{H}^+$) and a $\text{pH} < 7$.

Basic Solution

An alkaline solution characterized by a high concentration of hydroxide ions ($\text{OH}^-$) and a $\text{pH} > 7$.

Buffer

A solution or substance (such as the bicarbonate buffer system) that helps maintain a stable pH level by absorbing or releasing hydrogen or hydroxide ions.