1. Chapter 5 Section 1 -In chemistry we must believe in things we cannot see -matter is made up of such tiny particles -everything is made up of matter -matter is composed of atoms atom- the smallest particle of an element that retains the properties of that element -atom in Greek means unable to cut -can fit 100,000,000 atoms in a 1 cm space

2. -atoms can only be viewed using special microscopes -page 108 figure 5.3 -Greek teacher Democritus first suggested the existence of atoms -John Dalton discovered the atom 2000 years later -said that atoms are indivisible

3. Dalton’s Atomic Theory 1)all elements are composed of atoms 2)all atoms of the same element are identical 3)atoms of different elements can combine to form compounds in simple whole number ratios 4)atoms can be separated, rearranged, or joined to form chemical reactions