Atoms and Subatomic Particles

A set of vocabulary flashcards covering key concepts related to atoms, subatomic particles, the periodic table, and changes of matter.

Proton

Positively charged particle in the nucleus.

Electron cloud (shell/energy level)

Region outside the nucleus where electrons are found.

Electron

Negatively charged particle, very small mass, in the electron cloud.

Atomic number

Number of protons, which gives the element’s identity.

Neutron

Neutral particle in the nucleus.

Nucleus

Dense center of an atom that contains protons and neutrons.

Mass number

Total number of protons and neutrons.

Period

Horizontal row on the periodic table.

Isotope

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

Group/Family

Vertical column on the periodic table with similar properties.

Ionic charge

Calculated as protons minus electrons; determines if atom is a cation or anion.

Cation

A positively charged ion (more protons than electrons).

Anion

A negatively charged ion (more electrons than protons).

Octet rule

Stable atoms want 8 electrons in their outer shell.

Physical change

No new substance formed (e.g., melting, boiling, cutting).

Chemical change

New substance formed (e.g., rusting, burning).