ELEMENTS OF LIFE

On the surface, a human and a rock seem to have very little in common. Yet at their most basic level, both humans and rocks are composed of chemical elements. There are now 112 recognized elements organized into eight different groups. Twenty-two of these elements are synthetic whereas the remaining ninety elements are found in nature. In the earth's crust, eight elements account for 98 percent of all matter. Approximately eleven elements account for the majority of chemicals in the human body.

Each element is composed of a specified number of protons, neutrons, and electrons. The elements are numbered according to the number of protons, and then organized by number into the periodic table of the elements.

ACTIVITY

In this exercise, you will use the Scholar Edition of WebElements to gather information about some of the elements found in the human body.

Use your browser to go to http://www.webelements.com/webelements/scholar/index.html.

Use the interactive periodic table to learn about the following elements: phosphorus (P), potassium (K), sulfur (S), iron (Fe) and calcium (C).

For each element, answer the following:

1. How many protons does this element have?
2. How many electrons does the element have in its outermost shell? (Use the "Electronic Data" link for each element.)
3. What is the biological role of this element? (Use the "Biology" link for each element.)
4. What is the total mass of this element in an average 70 kg human?