Chapter 2 Notes 2008 Place these notes into your Biology Notebook.

The smallest unit of a chemical element is called the atom. Neutrons are subatomic particles that lack an electrical charge. The net charge of the nucleus of any atom is positive. The electron carries a negative charge. Between neutrons, protons, and electrons, electrons have the smallest mass.

Protons and neutrons make up the nucleus of atoms. There are approximately 112 known elements, and more that are being discovered and studied. A chemical compound is a substance formed by the bonding of atoms in definite proportions. After atoms gain or lose electrons, they are called ions.

Sodium chloride is an ionic compound. Examples of molecules: C 6 H 12 O 6 H 2 H2OO2H2OO2 N2N2

The space surrounding the nucleus of an atom contains electrons. Democritus believed that atoms could not be divided.

If an atom contains 3 protons, 4 neutrons, and 3 electrons, its mass number would be 7. Isotopes are atoms of the same element with the same number of protons and a different number of neutrons. Valence electrons are electrons in the outer energy shell. These electrons are available to form bonds.

Compounds are substances formed by the combination of two or more elements in definite proportions Sodium chloride is considered to be a crystal and ionic compound. NaCl The physical and chemical properties of a compound are usually very different from those of the elements from which it is formed. Water is made up of two atoms of hydrogen and one atom of oxygen.

If an atom contains 11 protons and 12 neutrons, its atomic number is 11. Ice floats on water because water expands when it freezes. If you stir salt into boiling water, you produce a mixture called a solution. A solution is an evenly distributed mixture of two or more substances. When salt is dissolved in water, water is the solvent and salt is the solute.

In chemical reactions, atoms are rearranged. Chemical reactions that release energy often occur spontaneously. Heat, light, and sound are all forms of energy that can be released during a chemical reaction. While preparing a cell culture, a scientist places a colony of bacteria into distilled water and stirs it up. This mixture of water and living cells is called a suspension.

A map of eastern North America, showing the pH of rainfall in the various states, indicates that the pH of rain in New York State varies from 4.22 to According to these figures, the most acidic rainfall in New York State has a pH of 4.22.

Proteins help to fight disease. Proteins control the rate of reactions and regulate cell processes. Proteins build tissues such as bone and muscle.

Enzymes are proteins that maintain a specific shape. The enzyme’s shape allow it to act as a catalyst to speed up chemical reactions. Enzymes work best at a specific pH. Catalysts lower the activation energy of a chemical reaction.

DNA and RNA are molecules made of nucleotides. Four macromolecules: Carbohydrates Proteins Nucleic Acids Lipids