What is the difference between Periods and Groups?

The ancient chemists used the concept of groups and periods to arrange the elements in rows and columns. The periods are horizontal rows, counting from left to right, while groups, also called families are vertical columns, counting from top to the bottom. We have seven (7) periods and eighteen (18) groups. The elements in a group have similar physical and chemical properties. The elements in the same periods share the same electron configuration, and they have equal numbers of valence electron.

Electronegativity increases as you go down the group, and decreases as you go up the group in the periodic table. Also, electronegativity increases as you go from left to right of the periods, and decreases as you go from right to left. As you go from left towards the right across the group on the periodic table, the proton and atomic numbers increase. When you go up on the periodic table, electron affinity increases, but as you go down the groups, the energy shells increase.