Atomic Structure 7th Grade Core Knowledge Curriculum

• Review (from grade 5): Structure of atoms: protons, neutron, electrons Molecules

Compounds are formed by combining two or more elements and have properties different from the constituent elements.

• Early theories of matter
The early Greek theory of four elements: earth, air, fire, and water Later theories of Democritus: everything is made of atoms and nothing else (“atom” in Greek means that which can’t be cut or divided); atoms of the same kind form a pure “element” Alchemy in middle ages

• Start of modern chemistry
Lavoisier and oxygen: the idea that matter is not gained or lost in chemical reactions John Dalton revives the theory of the atom.
Mendeleev develops the Periodic Table, showing that the properties of atoms ofelements come in repeating (periodic) groups.
Niels Bohr develops a model of the atom in shells that hold a certain number ofelectrons.

Bohr’s model, plus the discovery of neutrons, helped explain the Periodic Table: atomic number, atomic weight, and isotopes.