ATOMS& MOLECULES

Atom

The basic building block of matter and the smallest unit of an element that retains its chemical properties.

Subatomic Particles

The (3) main components of an atom: protons (positive charge), neutrons (no charge), and electrons (negative charge).

Atomic Number

The total number of protons found in the nucleus of an atom, identifying the element's position in the Periodic Table; represented by (Z).

Mass Number

The total number of protons and neutrons in an atom's nucleus, represented by (A).

Isotopes

Variations of a particular chemical element which share the same number of protons but have different numbers of neutrons.

Molecule

An electrically neutral group of (2) or more atoms held together by chemical bonds.

Compound

A substance formed when (2) or more different chemical elements are chemically bonded together in a fixed ratio.

Valence Electrons

The electrons located in the outermost shell of an atom which determine its chemical reactivity and bonding capabilities.

Covalent Bond

A chemical bond that involves the sharing of electron pairs between atoms.

Ionic Bond

A type of chemical bonding that involves the electrostatic attraction between oppositely charged ions, often resulting from the transfer of electrons.

Ion

When 2 or more atoms combine and gain a positive/negative charge

Law of Conservation of Mass

Mass can neither be created nor destroyed. In a chemical reaction, mass is conserved

Law of Constant Proportions

In a pure chemical compound, elements combine in fixed ratios by mass

Molecular mass

The sum of the atomic masses of all atoms in a molecule and is expressed in atomic mass units

Formula unit mass

The sum of masses of one formula unit of an ionic compound