Chemistry Module 2

Matter is composed of indivisible particles called _

Atoms

An _ consists of only one type of atom

element

The properties of one element _ from those of all other elements

differ

A _ consists of two or more elements combined in a small, whole-number ratio

compound

Atoms are neither created nor destroyed, but instead _

rearranged

Thomson’s Cathode Ray Tube

There are sub-atomic particles called electrons

Oil Drop Experiment

Charge of electron determined by Millikan

Rutherford’s Gold Foil Experiment

The atom is mostly empty space with protons in the nucleus

Chadwick

Atoms are neutral, neutrons are also in the nucleus

Proton (p or Z)

Nucleus, positive charge, mass of 1 amu, defines the element

Neutron (n)

Nucleus, neutral, 1 amu, determines Isotopes

Isotopes

An element with a different number of neutrons

Electron (e)

“orbits” the nucleus, negative charge, gain/loss of electrons yield ions

Cation

Loss of electrons, positive

Anion

Gain of electrons, negative

Atomic Mass Unit

very small mass defined for convenience to be appx. mass of a particle found in the nucleus of an atom

Atomic Mass

Appx. equal to its mass number