STUDY GUIDE Early Atomic Models (aka Theories)

Protons

Subatomic particles with a positive charge, approximately 1840 times larger than electrons.

Electrons

Subatomic particles with a negative charge, so small they behave like energy waves.

Neutrons

Neutral subatomic particles, roughly the same size as protons.

Atomic Number

The number of protons in an atom's nucleus, defining the identity of the element.

Mass Number

The total number of protons and neutrons in the nucleus of an atom, often referred to as atomic mass.

Isotopes

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

Ions

Atoms that have either lost electrons (cations) or gained electrons (anions).

Average Atomic Mass

The weighted average of the masses of an element's isotopes.

Democritus

An early Greek philosopher who proposed the idea that matter is made up of tiny, indivisible particles called atoms.

Rutherford's Gold Foil Experiment

An experiment that demonstrated the existence of a small, dense nucleus within the atom.

Bohr Model

A model of the atom that suggests electrons orbit the nucleus in distinct energy levels, likened to planets orbiting the sun.

Frequency (n)

The number of waves that pass a given point per second.

Wavelength (λ)

The distance between successive peaks of a wave.

Cation

An ion that has lost one or more electrons and thus has a positive charge.

Anion

An ion that has gained one or more electrons and thus has a negative charge.

Atomic Mass Unit (amu)

A unit of measurement for atomic mass, commonly referred to as 'u'.

___ are charged particles that can be either positively or negatively charged.

Ions

An atom's identity is defined by its ___ number.

Atomic

___ are atoms of the same element with different numbers of neutrons.

Isotopes

The ___ number is the total count of protons and neutrons in an atom's nucleus.

Mass

A ___ is an atom that has lost electrons and carries a positive charge.

Cation

In the Bohr model, electrons are thought to orbit the nucleus in distinct ___ levels.

Energy

The weighted average of the isotopes of an element is called the average atomic ___.

Mass

The distance between successive peaks of a wave is referred to as its ___.

Wavelength

An __ is an ion that has gained one or more electrons and carries a negative charge.

Anion