Examine the periodic trend for atomic radii. The atomic radius for each element generally decreases from left to right on the periodic table. The reason for this is that, from left to right, the value of the electronegativity increases. Electronegativity is the attraction an atom has for its electrons. The atoms to the right of the periodic table are more likely to attract electrons because they only need a small amount of electrons in order to achieve stability. The atomic radius for each element generally increases from the top to the bottom of each periodic group. The reason for this is that there is a decrease in electronegativity from the top to the bottom of each periodic group. In order to remember the trend for atomic radius, draw a horizontal arrow pointing left at the top of the periodic table and a vertical arrow pointing down next to the periodic table.
Write in the estimated sizes of the atomic radii for each element. In order to obtain a better idea of the trends in atomic radii for the periodic groups, write in each estimated atomic radius. You can find the estimated atomic radii for each element online or in a chemistry textbook.
Color each periodic group a different color. The groups are labeled one through eighteen, from left to right. Write the group number above each group. Then, color the groups in. For example, you may choose to color Group 1 blue, Group 2 green, and Group 3 yellow and proceed on through Group 18 with a different color for each group.
Analyze the representation of the atomic radii. When you show the atomic radii groups on a periodic table, explain how each column is colored differently because it represents a different group. Point to the atomic radii of the elements in one of the groups and show that from the top of the group to the bottom of the group, the atomic radii increase in size. The colors and labels you have created will help to demonstrate your objective more clearly.