Protons, Neutrons, and Electrons

Atoms are the fundamental building blocks of matter. Each atom consists of a nucleus, made up of protons and neutrons, surrounded by a cloud of electrons. Protons carry a positive charge, neutrons are neutral, and electrons have a negative charge.

• Protons determine the atomic number and the identity of the element.
• Neutrons add mass and can affect an atom's stability.
• Electrons occupy energy levels (shells) around the nucleus.

Isotopes and Ions

Atoms of the same element can have different numbers of neutrons (isotopes) or gain/lose electrons (ions).

• Isotopes have the same number of protons but different numbers of neutrons.
• Ions are charged atoms, formed by gaining or losing electrons.

Atomic Models

The model of the atom has evolved:

• Dalton's solid sphere model
• Thomson's plum pudding model
• Rutherford's nuclear model
• Bohr's model with defined orbits
• Quantum mechanical model

Real-World Connection

Understanding atomic structure helps explain why elements behave the way they do, from the color of fireworks to the way metals conduct electricity.