Chem1301 Chapter 2 pt.1

Atomic mass and structure

Plum Pudding Model

Atoms are made of a positively charged cloud and (-) are embedded at random. Incorrect model of an atom.

Nuclear Atom

Discovered by Rutherford in 1911. The center of the atom was a concentration of positive charges, being the neutron containing the (+). (N) are also in the nucleus and (-) orbit around the nucleus.

Relative Mass of (N)

1 amu

Relative Charge of (N)

0

Relative Mass of (+)

1 amu

Relative Charge of (+)

+1

Relative Mass of (-)

0

Relative Charge of (-)

-1

Types of Radioactive Emissions

Gamma Rays: high energy light

Betta Particles: high speed light

Alpha Particles: charge double that of (-) with opposite sign

Isotopes

Differ in amount of (N)

Ions

Gained or lost (-)

Cations

Positive charge (lost (-))

Cat-ions are Paw-sitive!

Anions

Negative charge (gained (-))

Onions taste bad!

Causes of Chemical Differences in Atoms

1. Number of (-)

2. Arrangement of (-)

Atomic Mass Formula

(+) + (N) = Atomic Mass

Atomic Number

Number of (+)