Unit 4 - Atomic Models

John Dalton

father of chemical atomic theory.

• Proposed that elements made of particles are called atoms

• Atoms of the same element have same properties at

• Atoms of different elements have different properties

Law of Definite Proportions

Atoms can combine in whole number ratio

Law of Multiple Proportions

Atoms of the same element can unite in more than one ratio with another elementt to form more than one compound1

Atom

The smallest particle of an element that retains the properties of the element

F

(T/F) The atom is indestructible and indivisible.

Plum Pudding Model; JJ Thomson; positive sphere of matter with negative electrons in it

Name; Who; What

Atomic Number

Number of protons

Atomic mass

The mass of one atom of an element relative to one atom of another element.

Mass number

Sum of protons and neutrons in an atom

Isotopes

Atoms of the same element but with a different mass number because of a different amount of neutrons

Atomic mass

___ of an element is the weighted average mass of the isotopes of that element.

Percent abundance

how much of that isotope there is out of that element

Average atomic mass = (% Abundance 1)(mass 1)+(% Abundance 2)(mass 2)

Average atomic mass formula

Leucippus and Democritus

First to propose that matter made of particles that could not be cut up any further. He called them “atomos”.

Aristotle

Proposed all matter consisted of four elements, earth, water, air, fire.

JJ Thomson

Used cathode ray to study atoms. He showed that there were smaller particles in atoms. Those charged particles were electrons.

Ernest Rutherford

Show particles in a thin sheet of gold foil and observed the pattern of scatter of the particles. He proposed that there was a very small dense nucleus with the electrons around the atom.

Isotope name

Element-Number

Isotope symbol