Electron dot structures Show only the valence (outer) electrons Dots around symbol Equal dots to group number
Elements within the same group have the same electron-dot structure.
Valence Electrons Valence electrons are the electrons in the highest occupied energy level of the atom. Last number in electron configuration Valence electrons are the only electrons generally involved in bond formation.
Two types of bonds Ionic: between a metal and a nonmetal, electrons are transferred Covalent: between two nonmetals, electrons are shared All bonds help fulfill the octet rule=all elements want 8 valence electrons Except H, He, Li, and Be that want only 2
A Positive Ion (Cation): An atom that has lost one or more electrons. + charge Metals form cations
Chlorine Atom Chlorine Ion Cl 1s 2 2s 2 2p 6 3s 2 3p 6
A Negative Ion (Anion) An atom that has gained one or more electrons. Negatively (-) charged. Nonmetals form anions
When Na, (11) loses its valence electron, what element does its configuration look like ? a. Neon b. Potassium c. Beryllium d. Sodium Check your Neighbor
Ionic Bonds Bonds that are formed by transfer of electrons from one element to the other. Each element as an ion has a complete octet after the transfer of electrons.
Ionic Compound dot structures 1. show dot structures of original elements 2. Show arrows where electrons move 3. Show ending charges
Example: Formation of Lithium Fluoride. Li. + : F :..
The Ionic Bond The electrical force of attraction between oppositely charged ions holds the compound together. Na + F−F−
Naming ionic compounds Put the metal name first Put the nonmetal name second but change the ending to –ide NaCl K 2 O
Ionic charges Group 1=+1 Group 2= +2 Group 13=+3 Group 14=+/-4 Group 15=-3 Group 16=-2 Group 17=-1
Writing the formula for ionic compounds Write down the symbols and charges Criss cross the charges ignoring the signs Don’t write as subscripts 1 If the two charges are the same value there are no subscripts.