Atoms, Molecules, and Chemical Bonds

Atoms, Molecules, and Chemical Bonds

The composition of matter and changes in its com-position are the focuses of the study of chemistry. If you understand chemistry, your understanding of anatomy and physiology improves. Chemical changes within cells influence body functions and the status of the body’s structures. Chemicals of the body include water, proteins, carbohydrates, lipids, nucleic acids, and salts as well as foods, drinks, and medications.

Elements are fundamental substances that com-pose matter. Copper, iron, gold, silver, aluminum, carbon, hydrogen, and oxygen are all examples of ele-ments. Most living organisms need about 20 elements to survive. TABLE 2-1 lists the major and trace elements required by the human body. The periodic table of ele-mentsis a tabular arrangement of the chemical ele-ments, and organized on the basis of atomic numbers, electron configurations, and recurring chemical prop-erties. The elements are presented in order of increas-ing atomic number, which is the number of protons in the nucleus (FIGURE 2-1).

Atoms are tiny particles that compose elements,and are the smallest complete units of an element that retain its properties and vary in size, weight, and interaction­ with other atoms. The characteristics of living and nonliving objects result from the atoms they contain and how those atoms combine and interact. Thus, by forming chemical bonds, atoms can combine with other atoms that are not similar to them