Chapter 2~The Chemistry of Life

2.1~The Nature of Matter

Atoms2500 years ago—Democritus called the smallest fragment the atom.

Atoms are very small (100 million atoms would only be about the width of your little finger)

Atoms are made of 3 subatomic particles (protons, neutrons, and electrons)

Protons are positively charged and are located in the nucleus.

Neutrons have no charge and are located in the nucleus

Electrons have a negative charge and are located around the nucleus.

Protons, Electrons, and Atomic Number are the same number in a neutral atom.

Protons + Neutrons = mass number

Chemical Element- pure substance that consists of one type of atom.

There are more than 100 elements found on the Periodic Table, but only about 24 are common.

Elements are represented by one or two letters.

C = carbon

H = hydrogen

Na = sodium

Hg = mercury

Isotope – atoms of the same element that have different numbers of neutrons

All isotopes of an element have the same chemical properties

Chemical Compounds- a substance formed by chemical combination of two or more elements.

Physical and chemical properties are different from the elements it is made of

Examples

Chemical Bonds are created by interaction between electrons

Two major types are:1. Ionic Bond – occurs when electrons are transferred, causes an electrically charged atom (called an ion)

2. Covalent Bond – occurs when electrons are shared (creates a molecule)