6.2 – Atomic TheoryScience 10 Mr. Francis

Atoms are made of component particles called subatomic particles: protons, neutrons, and electrons.

Every atom of any one element will have the same number of protons.

Positive protons and neutral neutrons are found in the nucleus, and negative electrons are arranged in shells or orbits around the nucleus.

There are an equal number of protons and electrons in an atom. Ions form when the number of electrons changes.

The number of electrons in the outer shell determines the properties of the element.

This one!

Atomic number is the smaller number shown with an element on the periodic table

Atomic mass is the larger number shown with an element on the periodic table

In an atom, both the number of protons and the number of electrons is equal to the atomic number

To find neutrons:

Neutrons = Atomic Mass – Atomic Number

We can show a particular atom in the form: Ag – 107

The symbol, Ag tells us what the element is (Silver)

We can refer to the periodic table to determine the atomic number which tells us the number of protons and electrons

107 is the atomic mass of this specific element of Silver

Even though the periodic table tells you that the atomic mass of silver is 107.9, that mass is an average of all known isotopes of Silver

Assignment

Atomic Theory Worksheet

P. 156 # 2, 3a,c,e, 4, 5, 7