Atomic Structure

An atom is the smallest unit of an element. It is built from three particles, and where they sit matters.

• ●Protons: positive charge, found in the nucleus (the center).
• ●Neutrons: no charge (neutral), also in the nucleus.
• ●Electrons: negative charge, zooming around the nucleus in the electron cloud.

Atomic Number and Mass Number

• ●Atomic number = the number of protons. This is what makes an element that element. Every carbon atom has 6 protons.
• ●Mass number = the number of protons plus the number of neutrons.
• ●In a neutral atom, the number of electrons equals the number of protons.

Isotopes

Isotopes are atoms of the same element that have different numbers of neutrons. They have the same atomic number but a different mass number. Carbon-12 and carbon-14 are both carbon, but carbon-14 has two extra neutrons.