molecules and ions

mixture

can be separated by phy method

not uniform

heterogenous

uniform

homogenous

pure substance

cannot be separated bt phy method

can be decomposed by chem process

element

cannot be decomposed by chem process

compound

can be from by ionic bonding

transfer of electron

element combine chemically

differ from constituent element

constant composition

smallest particle found

molecule

form from covalent bonding

sharing of electron

atom

same atomic no

different mass no

different no of electron

smallest particle in element

structure

proton (P)

charge +1

electron (E)

charge -1

surround nucleus

nuetron (N)

charge 0

P+E = nucleus

No.P = No. E

No. P+ No.N = mass no

weight average mass of an element