What is the purpose of arranging elements in columns on the periodic table?

How are periods and groups defined on the periodic table?

Explain the trend in metallic character of elements as you move across a period on the periodic table.

What are metalloids or semi-metals and where are they located on the periodic table?

How can the periodic table be used to predict properties of elements?

Explain the relationship between the electronic configuration of elements and their position on the periodic table.

Describe the trend in reactivity of Group 1 metals as you move down the group.