Scientists

New Zealand

1887-1937

Prove something empty by putting something through it Thin gold sheets to not absorb bullet=target atoms Small particle is bullet with high energy=alpha particles Electrons affect it Most alpha particles through but some deflect

Nucleus-dense positive Center almost entire mass of atom (v=1/10 trillionth of an atom) Positive charge balances negative charge Electrons surround nucleus

Nucleus composed of protons and neutrons Protons number=electrons number Neutrons have no charge, mass a little more than a proton, and discovered by Chadwick in 1932

Used a cathode ray tube to study electricity “Crookes” tube Ray made of tiny negatively charged particles called electrons Smaller than hydrogen atoms Atoms divisible Atoms have same electrons Net charge 0 so pose and negative charge the same

Tiny and light compared to an atom Negatively charged Move fast

Cloud of positivity Atoms divisible Internal structure Electrons in positive field Positive and negative charge the same Atom "empty space"

Elements composed of atoms Tiny, hard, unbreakable, and spheres All atoms of one element the same Atoms of one element different from another element Atoms of one element form with atoms of another element to form compounds Law of Multiple Proportions-all samples of a compound contain same proportions in mass of the elements Atoms indivisible in chemical process Present at beginning then present at the end Rearranged Atoms of one element cannot change into atoms of another element

Determines chemical behavior because electrons participate in bonding

Determines the identity of the atom

Stabilize the nucleus or hold it together