Chapter 2: Chemistry of Life Section 2.1: Introduction to Chemistry Part II

The atoms of most elements link up with each other in different arrangements and combinations – these links are called chemical bonds.

When chemicals bond they form substances called chemical compounds. Atoms form bonds in an attempt to become more stable which means they seek to have a full out shell.

2 Types of Chemical Bonds Ionic

Ionic Bonds One must remember with ionic bonds the elements are constantly trying to make their outer shells stable!!! Atoms on the left side of the periodic table tend to give up or lose electrons. Atoms on the right side of the periodic table tend to accept or gain electrons

Ionic Bonds When an atom gains or loses an electron, the result is an ion. A negative ion has gained 1 or more electrons. A positive ion has lost 1 or more electrons. The strong attraction between oppositely charged ions is called an ionic bond.

2 Types of Chemical Bonds Ionic Covalent

Covalent Bonds When electrons are shared between atoms a covalent bond is formed. The more electrons in the covalent bond, the more strongly the 2 atoms are joined. Types: Single bond – share 2 electrons Double bond – share 4 electrons Triple bond – share 6 electrons

Covalent Bonds Not easy to break. A group of atoms united by covalent bonds typically acts as a single unit called a molecule. A molecule can contain from 2 to millions of atoms!

Chemical formula Shorthand notation to describe a chemical compound. Indicates the elements that form the compound and the proportions in which they combine. H2O2

Properties of Water Found in every living cell and outside most. Vital to life Polar molecule (see figure at right) Good at dissolving polar and ionic compounds