Using the Periodic Table

Carbon

How many elements have been discovered at present?

Have luster

Tend to gain electrons in chemical reactions

Scientist that classified some elements into groups of three called triads

Take up 3/4 of the elements on the periodic table

Semiconductors

Mendeleev organized the elements by

Have 2 valence electrons

Good conductors of heat

Have unpredictable properties

Moseley arranged the elements by

Usually quite brittle

Calcium

Has six valence electrons

Contains 2 elements

Are very unreactive

Tightly held valence electrons

Arsenic

Has only one electron