Families, which are the vertical lines on the Periodic Table, are also known as groups, have similar chemical properties. They also have similar reactivity. This is due to them all having the same number of valence electrons. 

Elements in the same period have the same level of orbital shells. Orbital shells are where the electrons can be pictured in a model. They're arranged from the atom with the least protons on the left to gradually increasing by one as it goes to the right.

Groups and Periods

The amount of protons an element has determines its atomic number. These positive subatomic particles can be found in the nucleus. They show the order of the element in the periodic table. The higher the number, the farther along they can be found in the periodic table. 

To sum up, the higher the atomic number, the farther along it is. The lower the atomic number, the closer the element is to the beginning. 

Role of Protons

As aforementioned, each Periodic Table group has the same number if valence electrons. Valence electrons are the electrons in the outer shell of the electron. Generally, as you move right in a period, each atom grows one more valence electron (to a certain point, where the cycle restarts.) In terms of reactivity, if an atom has a full outer shell (typically eight valence electrons) it is considered non-reactive. This is because it isn't looking to give away or take any electrons from other atoms. In the case of an atom without a full outer shell, they are reactive. 

Valence Electrons

Referencing the Table on the last page, one can say that nonmetals are on the far-right (not including hydrogen, on the top left), in blue. The metalloids are straddling the line between metals and non-metals in yellow. The metals fill the rest of the table, especially on the left and bottom. Metals are malleable, shiny, hard, and good conductors of electricity. Non-metals aren't good conductors, are brittle, and are non-malleable. Metalloids, on the other hand, are semiconductors, where they both insulate and conduct electricity.

Metals, metalloids, and non-metals

Alkali Metals,

Alkaline Earth Metals

Transition Metals

Boron Family

Carbon Family

Nitrogen Family

Oxygen Family

Halogens

Noble Gases

Family Names

Alkali Metals are found in the first group of the Periodic Table. These are characterized as being shiny, soft, silvery, highly reactive, and so soft they can be cut with a plastic knife. Potassium can be seen in this group, and is also seen in saline drips. Lithium, another element from the Alkali Metals, is used to make rechargeable batteries. To add to that, hydrogen, the first element in the entire periodic table is here, too.

Alkaline Metals are the second group. They are shiny, silvery-white, and relatively reactive, due to them only having to give away two valence electrons. Radium is there, which is used in radiotherapy. So is strontium, which makes the stunning reds you see in fireworks. Calcium appears in this group as well.