atoms

What is an atom?

The basic building block of all matter; it is the smallest part of an element that can exist.

Atomic Structure

Atoms consist of a central nucleus surrounded by electrons that orbit in specific layers called shells.

Subatomic Particle Properties

1. Proton
   • Relative Mass: 1
   • Relative Charge: +1
2. Neutron
   • Relative Mass: 1
   • Relative Charge: 0
3. Electron
   • Relative Mass: \frac{1}{1840}
   • Relative Charge: -1

What is the Nucleus?

The small, dense center of an atom containing protons and neutrons. It holds almost all of the atom's mass.

Atomic Number

The number of protons in an atom. It is unique to each element and determines its identity.

Mass Number

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

Overall Charge of an Atom

Atoms are neutral because the number of positive protons equals the number of negative electrons, meaning the charges cancel out.

Electron Shell Rules

Electrons fill shells starting from the one closest to the nucleus:

• 1st Shell: Holds up to 2 electrons
• 2nd Shell: Holds up to 8 electrons
• 3rd Shell: Holds up to 8 electrons

What is an Element?

A substance made up of only one type of atom, such as pure gold or oxygen gas.

What is a Compound?

A substance formed when two or more different types of atoms are chemically bonded together.