Elements and Atomic Number Summary

Atomic Structure

• Atoms are defined by protons, neutrons, and electrons.

• Atomic Number (Z): Number of protons in an atom's nucleus, determines element identity.

• Mass Number (A): Total number of protons and neutrons.

Key Concepts

• All atoms of the same element have the same number of protons (same atomic number).

• Atoms are electrically neutral (equal protons and electrons).

• Ions are charged atoms with unequal numbers of protons and electrons.

Isotopes

• Isotopes are atoms of the same element with different numbers of neutrons, hence different mass numbers.