1. Forming Chemical Bonds

2. Reactivity How atoms interact with other atoms
Dependent on the number of valence electrons (“eight is great”)
Noble gases are chemically stable because they have 8 valence electrons called an octet
Elements will react (gain/lose/share) to acquire a full octet of electrons
Atoms in the same group have similar chemical properties because they have the same number of valence electrons
Last unit we talked about stability in the nucleus of an atom. This chapter we are talking about stability within an atoms electron configuration.

3. Valence Electrons
Electrons in the outermost energy level (highest n shell)
These electrons participate in chemical reactions and determines the chemical properties of an element
To identify look at group number (representative elements only, group A)

4. Cations and Anions Of Representative Elements+1 +2 +3 -3 -2 -1

5. Lewis dot symbol Example row
Where do we get the number of valence electrons?

6. Compounds Two or more different elements that combine chemically
Can be broken down by chemical means
Has properties different from those of its component element

7. Binary Compounds Combination of atoms from just two different elements
ex) CO2 , NaCl , Fe2O3

8. Chemical Formula
Expresses the composition of substances in terms of their chemical symbols
Smallest representative unit of a substance
Subscripts denote number of atoms
Mg3N2
Mg3(PO4)2
Numbers outside of the parentheses get multiplied in

9. Chemical Bonds Force that holds two atoms together
Only involve valence electrons

10. Transfer (gain/lose) of electrons
Chemical Bonds
Ionic bonds
Transfer (gain/lose) of electrons
Covalent bonds
Sharing of electrons
Metallic bonds
Sea of electrons
What is a chemical bond?
What is formed when these atoms are held together?

11. the electrostatic force that holds ions together in an ionic compound
Ionic Bonds
the electrostatic force that holds ions together in an ionic compound

12. *Electrons are transferred from a metal to a nonmetal

13. Ions Variation in the number of electrons
Anion
Cation
gain of electrons
overall charge is negative
Tend to be nonmetals; reactivity of a nonmetal is based on the ease in which they accept an electron
lose of electrons
overall charge is positive
Tend to be metals; reactivity of a metal is based on the ease in which they lose their valence electrons 1+ Na 1− F

14. A monatomic ion contains only one atom:
Na+, Cl-, Ca2+, O2-, Al3+, N3-
A polyatomic ion contains more than one atom:
OH-, CN-, NH4+, NO3-
*These ions are charged molecules, and located on the back of your periodic table

15. Ionic Compounds
composed of cations and anions held together by ionic bonds
Usually a metal and nonmetal
Electrically neutral

16. Lowest whole-number ratio of ions in an ionic compound
Formula Unit
Lowest whole-number ratio of ions in an ionic compound
Atoms
Cation
Anion
Ratio
Formula Unit
Na and O
Al and Br
Mg and N
Ionic compounds carry what charge?
So this means our cations and anions have to do what?

17. Properties of Ionic Compounds
Strong bonds
High melting and boiling points
Crystalline solid at room temperature
Hard, rigid, and brittle
When dissolved in water or melted it can conduct an electric current

18. Electrolyte
An ionic compound whose aqueous (water) solution conducts an electric current
All stalts are ionic compounds but not all ionic compounds are salts

20. Crystal Lattice Shape of ionic compounds Repeating 3-D pattern
very stable due to the large attractive forces between ions
NaCl and CsCl shown above
Where do these attractive forces come from?