Dalton's Atomic Theory and Atomic Structure

This page introduces John Dalton's atomic theory and the basic structure of atoms. Dalton proposed that all elements are composed of tiny, indivisible particles called atoms. He stated that atoms of the same element are identical, while atoms of different elements have distinct properties. According to Dalton, chemical reactions occur when atoms are separated, joined, or rearranged, but atoms themselves are not changed into other elements during reactions.

The modern definition of an atom is provided as the smallest particle of an element that retains its identity in a chemical reaction. The page then describes the structure of the nuclear atom, introducing the three main subatomic particles:

1. Electrons: Negatively charged particles responsible for bonding
2. Protons: Positively charged particles found in the nucleus
3. Neutrons: Neutrally charged particles found in the nucleus

Definition: An atom is the smallest particle of an element that retains its identity in a chemical reaction.

Highlight: The nucleus contains protons and neutrons, while electrons orbit around it in energy levels called shells.

Vocabulary: Valence electrons are the outermost electrons of an atom, which are involved in chemical bonding.