Atom Structure

Democritus

atomos (atoms)

Platos and Artistotle

rejected atoms

1700 AD

atoms become accepted (pure substances and 3 basic laws of matter)

Law of conservation of mass

mass is neither created nor destroyed; mass of reactants = mass of products

Law of constant composition/definite proportions

specific compounds have a definite chemical composition by mass; ratio of elements in a compound will always be the same

law of multiple proportion

when same elements combine to create 2 different compounds, mass ratio of same element in both compounds is always a whole number ratio

John dalton

first unified atomic theory

1. All elements are made of atoms; the atom is indestructible

2. Atoms of 1 element are identical; atoms of different elements are different

3. Atoms combine to form compounds in simple whole number ratios

4. Chemical reactions occur when atoms rearrange

modern atomic theory

atoms are broken into subatomic particles; atoms of a element are not always identical due to isotopes; atoms can change into other atoms from nuclear reaction

electron cloud

bigger than nucleus but almost massless; surrounds nucleus; negatively charged

cation

positively charged ions; remove electrons

anions

negatively charged ions; add electrons