Chapter 6:

An Introduction

to Atoms

Atomic Theory Development

• Key Players–Democritus–Dalton– Thomson–Rutherford–Bohr

the atom

• Literally means…– Not able to be divided

• It is the smallest item that

an element can be divided

and still be the same

element.

the atom

• How small is an atom?

JJ Thomson

• Plum Pudding Model– Aka Chocolate Chip Ice Cream Model

Ernst Rutherford

• at the center of an atom–Nucleus

Subatomic particles

• Protons– Positive charge

• Neutron– Neutral charge

• Electron– Negative charge

the atom

Subatomic particles

• Location– Nucleus• Protons & neutron

– Electron Cloud• Electron

• Mass– Only protons and neutrons are measurable– Electrons way too small to measure

Isotopes

• Protons stay the same but…– Neutrons either increase or decrease– Changes the atomic mass

isotopesWhat is this

element?

Silver

What is the atomic mass of

this isotope?

108

atomic measurement

Atomic Mass Unit

Atomic Mass

Mass Number

atomic measurement

• Atomic Mass Unit– Unit that describes the mass of an atom

• Atomic Mass– Weighted average mass of all natural isotopes of

an elements• Mass Number– Sum of the protons and neutrons

Mass number

Mass Number…… 13

# of Protons……… - 6_____________________# of Neutrons….. 7

Terms to Know

Atom

Electrons

Electron Cloud

Isotopes

Protons