Chem S1

Atom

The basic unit of matter, consisting of protons, neutrons, and electrons.

Subatomic Particles

Particles smaller than an atom; includes protons, neutrons, and electrons.

Protons

Positively charged particles found in the nucleus of an atom.

Neutrons

Neutral particles located in the nucleus of an atom.

Electrons

Negatively charged particles that orbit the nucleus in energy levels or shells.

Atomic Number

The number of protons in an atom, defining the element.

Mass Number

The total number of protons and neutrons in an atom's nucleus.

Isotopes

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

Electron Configuration

The distribution of electrons among the orbitals of an atom.

Valence Electrons

Electrons in the outermost shell that determine an atom’s chemical properties.

Ions

Charged particles formed when atoms gain or lose electrons.

Cation

A positively charged ion formed when an atom loses electrons.

Anion

A negatively charged ion formed when an atom gains electrons.

Nuclear Forces

Strong forces that hold protons and neutrons together in the nucleus.

Electromagnetic Forces

Forces between protons and electrons that keep electrons in orbit around the nucleus.

Periodic Table

A chart that arranges elements by increasing atomic number and groups them by similar properties.

Aufbau Principle

Electrons fill the lowest energy orbitals first before moving to higher ones.

Pauli Exclusion Principle

No two electrons in an atom can have the same set of four quantum numbers; each orbital can hold a maximum of two electrons.

Hund’s Rule

Electrons will fill degenerate orbitals singly first before pairing up.

Atomic Radius

The distance from the nucleus to the outermost shell of electrons.

Ionization Energy

The energy required to remove an electron from an atom.

Electronegativity

The tendency of an atom to attract electrons in a chemical bond.

Ionic Bonding

A bond formed when one atom gives away electrons and another atom takes them, resulting in oppositely charged ions.

Covalent Bonding

A bond formed when two atoms share electrons with each other to fill their outer shell.

Polar Molecule

A molecule that has a positive end and a negative end due to differences in electronegativity.

Non-Polar Molecule

A molecule that does not have positive and negative ends; electrons are shared equally.

Lewis Structure

A diagram that shows how atoms in a molecule are connected by shared electrons.

Lattice Structure

A repeating structure where each positive ion in an ionic compound is surrounded by negative ions.