DEVELOPMENT OF ATOMIC THEORY & ATOMIC STRUCTURE

Democritus

matter is made of tiny, indivisible molecules called atoms

Aristotle

matter is made of only four elements (fire, earth, water, air)

John Dalton

atoms of the same elements are identical combined in fixed ratios

• The Solid Sphere Model

Joseph John Thomson

electrons are embedded in a positively charged sphere. Discovered electrons

• Plum Pudding Model

Ernest Rutherford

discovered the dense, positively charged nucleus. Discovered nucleus

• Nuclear Model

Niels Bohr

electrons move in fixed energy levels (orbits) around the nucleus

• Planetary Model

Erwin Schrodinger

• electrons do not orbit the nucleus (probability cloud)

• Quantum Mechanical Model of an Atom

Electron charge

negative

Proton charge

positive

Neutron charge

no charge

Atom charge

neutral (protons=electrons)

Ions

charged atoms

Z

atomic number

A

atomic mass (Z/P/E + N)

P

protons

E

electrons

N

neutrons (A - Z/P/E)

Isotopes

same protons, different neutrons

period

rows (7 of them)

groups/family

columns

group A

representative elements, blocks s and p

group B

transition metals, blocks d and f

valence electrons

total of superscripts of energy level

chemical bonds

Forces of attraction that holds atoms together

ionic bonds

transfer, metal + nonmetal

covalent bonds

share, nonmetal + nonmetal

octet rule

for an atom to be stable, they should have eight valence electrons in the outermost shell/energy level