COMPOUNDS 5.6 REMEMBER • The valence electrons are the most important. • Atoms tend to react with other atoms in order to get a full outer electron orbit. • Metals loose electrons to produce cations • Non-metals gains electrons to become anions • Sometimes non-metals will share with other non-metals LEWIS STRUCTURES • We can write a short form of Bohr-Rutherford diagrams that only includes the valence electrons Metal Non-metal Li S Mg C COMPOUNDS • A compound is a substance made up of two or more elements in a fixed ratio. • Examples of compounds include • water (H2O) • carbon dioxide (CO2) • sodium chloride (NaCl) • sodium bicarbonate (NaHCO3) • There are two main types of compounds. Ionic Compounds and molecular Compounds We will start with ionic and learn about molecular in a few days IONIC COMPOUNDS • Ionic compounds form when electrons are transferred from a metal to a positive ion and a negative ion. The oppositely charged ions are held together by an the attraction of the positive and negative ion. This is called an ionic bond. • Ionic compounds are made when large numbers of sodium and chloride ions join together to form an ionic crystal. An example is NaCl, sodium chloride. • Looking at one NaCl particle, we see that the ionic bond between the sodium cation and the chloride anion is formed by the transfer of an electron from the metal to the nonmetal. • Another example of an ionic compound is AlCl3, aluminum chloride. • An aluminum ion bonds with three chloride ions so that the sum of all charges in the chemical formula of the ionic compound is equal to zero. PROPERTIES OF IONIC COMPOUNDS • Ionic bonds are very strong, resulting in the following physical properties: • hard • brittle • high melting points (most ionic compounds are solids at room temperature) • Some ionic compounds are soluble in water. • When ionic compounds dissolve, they produce a solution that conducts electricity. Such substances are known as electrolytes.
