1. How Atoms Combine Nelson: Science Perspectives 9 – Pg. 263 - 266

2. Why Do Atoms Combine? Atoms combine to become more stable Elements that do not have the max. number of electrons in the outermost orbits combine with other elements to obtain this max. number. Atoms become more stable by gaining, losing, or sharing electrons (depending on if they are metals or non-metals)

3. Metals and Metals Metals form mixtures with other metals (a.k.a. alloys) Created by melting and mixing two or more metals and allowing them to solidify) Different from compounds because alloys are solutions of metals and do not combine chemically Example: Sterling silver is a solution of 92.5% silver and 7.5% copper

4. Metals and Non-Metals Metals lose electrons and become cations Non-metals gain electrons and become anions Cations and anions attract due to opposite charges Multiple ions can combine to form large crystals Example: Sodium Chloride (NaCl)

5. Chemical vs. Common Names Many ionic compounds have both chemical and common names Examples: NaCl  sodium chloride  table salt KCl  potassium chloride  potash (fertilizer) CaO  calcium oxide  quicklime (masonry) NaOH  sodium hydroxide  lye (drain cleaner) Chemical Names: (simple rules  more to learn in gr. 10) 1)Write the name of the metal first 2)Write the name of the non-metal and change its ending to –ide EXAMPLE: Sodium Chloride

6. Criss-Cross Method for Chemical Formulas Write the ionic charge Write the symbol for the metal first and the non-metal second Criss-cross to form the subscripts

7. Practice!!! Mg + O Li + N K + O

8. Non-Metals and Non-Metals Non-metallic elements do not become ions when combining with other non- metallic elements Instead, the nucleus of one atom forms a strong attraction to an electron in the outermost orbit of another atom and vice versa THINK: “tug-of-war” The electron(s) is/are shared

9. Non-Metals and Non-Metals Covalent bond  a bond formed when two non-metal atoms share electrons When atoms bond in this way they form molecules

10. Video: LINK: https://www.youtube.com/watch?v=QXT4OVM4vXIhttps://www.youtube.com/watch?v=QXT4OVM4vXI

11. Textbook Questions: Textbook: Pg. 266Questions: #2, 3 (refer to page 265), 5, 6, 9, 10