Radioactivity

Atomic Structure

An atom is the smallest unit of an element that can still be recognized as that element. Atoms are made up of three main subatomic particles:

• **Protons**: Positively charged particles found in the nucleus of an atom. The number of protons in an atom's nucleus determines the element.
• **Neutrons**: Neutral particles found in the nucleus of an atom. The number of neutrons can vary, resulting in different isotopes of the same element.
• **Electrons**: Negatively charged particles that orbit the nucleus in defined energy levels or shells.

Atomic Number and Mass Number

• **Atomic Number**: The number of protons in the nucleus of an atom, which determines the element.
• **Mass Number**: The total number of protons and neutrons in the nucleus of an atom.

Isotopes

Isotopes are atoms of the same element with the same number of protons but a different number of neutrons. This means they have the same atomic number but different mass numbers.