Explain how the group in which an element is located relates to the number of valence electrons in its outer shell.

The group number of an element in the periodic table corresponds to the number of valence electrons in its outer shell.

Step 1: Understanding the Periodic Table The periodic table is divided into groups (columns) and periods (rows). The groups are numbered from 1 to 18 from left to right.

Step 2: Understanding Valence Electrons Valence electrons are the electrons in the outermost shell of an atom. These electrons are important because they are involved in the formation of chemical bonds with other atoms.

Step 3: Relation between Group Number and Valence Electrons For elements in groups 1 and 2, the group number is equal to the number of valence electrons. For example, hydrogen and lithium are in group 1 and have one valence electron. Beryllium and magnesium are in group 2 and have two valence electrons.

For elements in groups 13 to 18, the number of valence electrons is equal to the group number minus 10. For example, carbon is in group 14 and has four valence electrons (14-10=4). Oxygen is in group 16 and has six valence electrons (16-10=6).

Note: The elements in groups 3 to 12 are known as transition metals and their valence electrons can vary.