It’s time to talk about Bonds… Chemical Bonds Chemical Bonding: The Formation of Compounds

Why do elements form bonds? All atoms want a full outer energy level 8 electrons, with the exception of H, He, Li, Be, & B Done by losing, gaining, or sharing electrons to obtain a complete valence shell. There are two different types of bonds that can be formed between elements…

Ionic vs. Covalent Ionic Covalent Formed by lost or gained electrons Involves a metal and a nonmetal (cation & anion) Very strong bond (strong attraction) due to opposite electronegativities) Ionic compounds have high melting points Solids at room temperature Dissolve into ions in water Covalent Formed by shared electrons between two atoms Involved two nonmetals (anion & anion) Weak bonds due to low attraction (similar electronegativities) Covalent compounds have lower melting points Mostly gases or liquids at room temperature. Do NOT dissolve into ions in water

Why do metals become cations? Because of their number of valance electrons, it is easier for metals to lose then to gain to get to 8. FOR METALS: the number of valance electrons LOST to get to 8 is the CHARGE of the ION.

Cation Formation Practice What charge will the metals below have when forming an ion? Al Sr Mg Li Pb Ba

Why do non-metals become anions? Because of their number of valance electrons, it is easier for nonmetals to gain valance electrons get to 8. FOR NONMETALS: the number of valance electrons GAINED to get to 8 is the CHARGE of the ION.

Anion Formation Practice What charge will the nonmetals below have when forming an ion? Cl N P O Se Br

Writing Ionic Formulas Steps to writing an Ionic Formula: Determine the charge of the cation and the charge of the anion (if not already given) Write the symbol of the cation first, then the symbol of the anion second “Criss-Cross” charges and write as neutral subscripts. Reduce subscripts (if possible)

Criss-Cross Method Na +1 Cl -1 Na Cl 1 1 NaCl

Na Cl Na Cl - + Bond Formation The opposite charges attract one another for create a bond Na Cl

Criss-Cross Method Mg +2 F -1 Mg F 2 1 MgF2