Relationships Among Elements

Periodic Trends: Graphing Atomic Radii

The periodic table is a wonderful source of information about all the elements scientists have discovered. In this activity, you will investigate the relationship among elements’ atomic numbers, radii, and positions in the periodic table.

The radii for elements with atomic numbers 3-38 are given in table 1. The radii are so small that a very small metric unit called a picometer is used. A picometer (pm) is one trillionth of a meter (1 x 10-12 m).

In this activity, you will graph the atomic radii of the elements with atomic numbers 3-38 and examine the graph for repeating patterns.

Table 1: Atomic Radii

Name and symbol

Magnesium Mg

Procedure

1. Make a graph of atomic radius v. atomic number using the above data. Choose an appropriate scale.

1. Label each point with the corresponding element symbol. When you have finished plotting points, connect the plotted data to create a line graph.

Periodic Trends: Graphing Atomic Radii

Questions and Conclusions:

1. Look at the shape of your graph. What patterns do you observe?

1. What family is represented by the high peaks on your graph? ______

1. What family is represented by the low peaks on your graph? ______

1. What family is represented by the smaller peaks just before the high peaks in your graph?______

1. What do you notice about the radii of the elements at the high peaks as you move from left to right on your graph? Look at your periodic table and find the element that represents each high peak. Where does each high peak begin in the periodic table?

1. What happens to the radii of the elements between two highest peaks? What does each of these groups of elements represent?

1. How can graphs such as the one you made help to predict the properties of elements that have not been discovered yet?

1. How do the radii of metals in each period compare with the radii of nonmetals in that period?

Source: Glencoe/McGraw-Hillpp. 21-22