BONDS

Chemical bonding Joining of atoms to form new substances A force of attraction that holds atoms together Atoms bond to each other based on their valence electrons (electrons in outer energy level) Atoms bond by gaining, losing, or sharing electrons to fill outer energy level with 8 electrons. (except H and He which need 2)

Three Types of Bonds Ionic Covalent Metallic

Ionic bonds – loss and gain Ion- charged particles, a charged atom Ionic bonds are a force of attraction between ions In ionic bonding a transfer of electrons occurs, an atom gains electrons while the other loses electrons Bonds between metals and nonmetals

Example of ionic bonds Static cling, casts, and seashells Salt (NaCl)- Sodium(Na) is in group 1, chloride(Cl) is in group 7 Losing an electron makes the atom a positive ion, gaining turns it into a negative ion. But combined the compound is neutral. Usually metal to nonmetal : the metal loses the electron and the nonmetal gains it

Covalent Bonds - share Co means to share Electron dot diagram is used to represent shared electrons These bonds are called molecules Shared electrons are attracted to the nuclei of all atoms involved Ex. Water (H O), sugar, carbon dioxide (CO ) Nonmetal to nonmetal 2 2

Metallic - Pool Form a pool of electrons which gives metallic bonds unique characteristics These bonds are malleable (can be hammered into thin sheets) and ductile (can be drawn into a wire) The pooling (free moving )allows electrons to flow easily so they don’t break and carry electricity well Ex. Copper, aluminum, gold Metal to metal

Electron Dot Diagram Shows an atom and the electrons in its outer energy level Shows symbol of atom and dots around it to represent electrons Remember, group/family # tells us how many valence electrons (which tells us what type of bond will form)

How to write electron dot diagram Start by putting one dot at the top of the symbol Then add dots around the symbol in the shape of a box (one one the right, bottom, left) Add fifth dot to top to make a pair * you should never have more than eight dots around the symbol

Dot diagrams Na C Be Br Sb