The Abundance of Elements in the Sun

The Arthur Ross Hall of Meteorites: Educator's Guide: Activity

Overview: Scientists seek to understand what the universe is made of. They try to determine the relative abundances of the different elements. However, there is no way to measure the composition of the universe as a whole, because different objects have different compositions. The different compositions reflect the different environments in which these objects formed and their different histories. Matter clumps together in the form of stars, gas clouds, planets, comets, asteroids, and meteors. Scientists determine the composition of those objects, and ultimately attempt to deduce the overall make-up of the universe.

Resource:
This activity will provide students with practice in reading and interpreting a graph showing elemental abundances.

Distribute copies of the periodic table and the graph below to students.

Point out that the graph is another way of showing the elements. This particular graph shows the current composition of the sun. Instruct students how to read the graph if they do not already know. Point out that the elements are listed according to atomic number along the X-axis. The Y-axis indicates the abundance of each element using powers of 10. The number 4 along the Y-axis represents 10⁴. Have students find argon (Ar) on the graph. Its abundance is graphed at 4 or 10⁴. Carbon (C) is graphed at about 7 or 10⁷. Ask them to find how much more carbon there is than argon. (10 to the 7th power (carbon) is 10,000,000. 10 to the 4th power (argon) is 10,000.)

Have students compare the graph to the periodic table. Use the following questions to guide a discussion:

• Which is the most abundant element in the sun?
• What is the atomic number of that element?
• Which is least abundant element in the sun?
• What is the atomic number of that element?
• What happens to the abundance of elements as their atomic numbers increase? (Their abundance decreases).

Have students use the graph to find the abundance of the following elements: hydrogen, helium, aluminum, gold. Have them determine the following:

• How much more hydrogen is there in the sun than helium?
• How much more hydrogen is there in the sun than aluminum?
• How much more hydrogen is there in the sun than gold?

Suggest students further investigate the processes in our universe that create these elements. Have students visit the web site:http://imagine.gsfc.nasa.gov/docs/teachers/elements/imagine/01.html There they can discover the elements that were created in the Big Bang, small stars, large stars supernovae and cosmic rays.