Who is the "Father" of the 

Periodic Table?

Dmitri Mendeleev

How did Henry Mosley arrange 

the elements?

by atomic number

Are the atomic number,the number of protons

and the number of electrons the 

same in an element?

yes

How many known elements 

are there?

115

How many elements are 

naturally occurring?

92

Where are the most reactive

elements found?

lower left

and 

upper right

(not Group 18)

Where are the metals found?

the lower left of the 

"staircase"

What % of all elements

are metals?

80%

Where are the 

non-metals found?

upper right of 

the "staircase"

What have properties of

both metals and non-metals?

metalloids

What are the vertical columns

called?

Groups

(also families)

How many groups are there?

18

Does every group

have the same number of electrons

in their outer shell?

yes

Groups 3 to 12 have a special 

name.  What is it?

transition metals

What are the horizontal rows called?

periods

How many periods are there?

7

Group 18 has three names.

What are they?

Noble or stable or inert gases

What is different about the Lanthanoid

and Actinide series?

they are very long