The Periodic Table

Mr. Fox Science Class

Looking for the Pattern

• Remember back to Friday– Valence Electrons– Dot Models of Elements– What do you see when you set up the elements

like they are on the table?

Dmitri Mendeleev

• Russian Scientist in 1869 found a pattern in the elements himself.

• Evidence of the Patterns– Similar chemical and physical properties– Atomic mass – Bonding power (dot models)

Atomic mass – average mass of one atom of an element.

He noticed that patterns appear when the elements were arranged in order of increasing atomic mass.

Periodic Table Today

How to read the table

The stuff

• Chemical Symbol – the one or two letters that stand for an element. Ex: Fe = iron K = potassium

• Atomic Number – number of protons in a nucleus of an atom

• Atomic Mass • Element’s Name

Other things you might see.

• Ion charges • Bonding power• Chemical activity• Size of atom

Organization of Table

• Group – (AKA families)• They are shown in columns on the periodic

table• Each of the elements have similar chemical

properties• Ex: group 18 elements do not react with other

chemicals normally.

Organization of Table

• Period• Horizontal rows across the table• Properties change as you move along a period.• They are predictable• Ex: as you move from the left to the right, the

elements get less reactive. The atoms get larger.

Valence Electrons

• Each group of the periodic has the same number of valence.

• Dot Models showed this to scientists• The real pattern that comes out