1. Chapter 23 Chemical Bonding
Electrons can be described as occupying a series of shells.
Electrons in the outermost shell are called valence electrons and the shell they are in is called the valence shell.

2. Chapter 23 Chemical Bonding

3. Chapter 23 Chemical Bonding
We represent valence electrons in an electron dot diagram.
Chlorine has three nonbonding pairs and one unpaired electron which will tend to want to bond.

4. Chapter 23 Chemical Bonding

5. Chapter 23 Chemical Bonding
Ion Formation:
When an atom has the same number of protons and electron, it is electrically neutral.
When atoms lose or gain electrons they form ions.
Ions are written as follows:
Fˉ, Ca²+, Clˉ, O²ˉ
Atoms tend to lose or gain electrons so that they end up with the outermost occupied shell filled and stable.

6. Chapter 23 Chemical Bonding
Ion Formation:
Group 1: likes to become +1 (Cations are +)
Group 2: likes to become +2
Transition metals usually +2 or +3
Group 13: can become +3, but usually covalently bond
Group 14: Covalently bond
Group 15: N and P can become -3
Group 16: likes to become -2 (Anions are -)
Group 17: Likes to become -1
Group 18: Not reactive (outer shell full)

7. Chapter 23 Chemical Bonding

8. Chapter 23 Chemical Bonding
Ionic bonding: When a bond is formed due to the electrical attraction after one atom loses an electron to another atom forming two oppositely charged ions.

9. Chapter 23 Chemical Bonding
Realistically, ionic bonds are formed as a highly ordered, three-dimensional grouping (Ionic crystal) like the above pictures, not one at a time like on the previous slide.

10. Chapter 23 Chemical Bonding
Ionic bonds are usually made from a metal and a non-metal
Metals like to become positive ions and nonmetals (if not sharing electrons to form covalent bonds), will gain electrons to become negative ions.

11. Chapter 23 Chemical Bonding

12. Chapter 23 Chemical Bonding
Naming Ionic Compounds:
The cation (the positive one) always goes first
The anion (the negative one) goes second and usually ends in -ide
Add subscripts to make sure the positive and negative charges cancel out to zero.
Examples:
Ca²+ and Iˉ gives us CaI2 and is called Calcium Iodide
Fe ³+ and O²ˉ gives us Fe2O3 and is called Iron (III) Oxide

13. Chapter 23 Chemical Bonding
3. K+ and S²ˉ gives us K2S and is called potassium sulfide
4. Ca²+ and O²ˉ gives us CaO and is called calcium oxide
5. Cu²+ and Clˉ gives us CuCl2 and is called copper (II) chloride
When cations have multiple charges (like transition metals), you designate the charge with a roman numeral after it.

14. Chapter 23 Chemical Bonding
Covalent Bonding: Atoms held together by their mutual attraction for shared electrons.
Covalent bonds are formed by two atoms that tend to gain electrons come into contact with each other.
They can’t effectively take an electron from one another so they share.
These are primarily nonmetals in the upper right-hand corner of the periodic table.

15. Chapter 23 Chemical Bonding

16. Chapter 23 Chemical Bonding
single covalent bond
Double covalent bond

17. Chapter 23 Chemical Bonding
Triple covalent bond

18. Chapter 23 Chemical Bonding
Naming Covalent Compounds:
We use prefixes to designate the number of atoms of each element we have.
mono = 1 hexa = 6
di = 2 hepta = 7
tri = 3 octa = 8
tetra = 4 nona = 9
penta = 5 deca = 10

19. Chapter 23 Chemical Bonding
Examples:
SiO2 is called Silicon dioxide
N2O3 is called dinitrogen trioxide
CF4 is called carbon tetrafluoride
Cl2O7 is called dichlorine heptoxide
P4S3 is called tetraphosphorus trisulfide
PCl5 is called phosphorus pentachloride
S2F10 is called disulfur decafluoride

20. Chapter 23 Chemical Bonding
Polar Covalent Bonding: Uneven sharing of electrons between two atoms.
In a molecule like H2, the two atoms share the electrons evenly.
In HF, the fluorine atoms pull the electrons closer to its side given the molecule a slightly negative charge on that side. The hydrogen side becomes slightly positive.
This separation of charge that happens in a polar covalent molecule is called a dipole.

21. Chapter 23 Chemical Bonding
This is a polar covalent bond
Notice the larger cloud around the fluorine atom because it has a greater need for that electron they share. Why?

22. Chapter 23 Chemical Bonding
Electronegativity – How strongly an atom is able to tug on bonding electrons . It can be measured.
The range of electronegativity is from 0.7 to 3.98
Electronegativity is greatest for elements in the upper right hand corner of the periodic table.
When two elements have the same electronegativity (usually the same element) it forms a nonpolar bond because the electrons are shared evenly.

23. Chapter 23 Chemical Bonding
Notice that the further apart two elements are on the table, generally the greater the difference in their electronegativities.

24. Chapter 23 Chemical Bonding
In Summary:
Ionic bonds have great differences in electronegativities to the point that one atom takes the other’s electrons. (metal/nonmetal)
Nonpolar covalent bonds have similar electronegativities and share evenly. (two nonmetals)
Polar covalent bonds have noticeable differences in electronegativities where one atom holds the electrons closer creating a dipole. (two nonmetals)

25. Chapter 23 Chemical Bonding
Water is a polar covalent molecule that has about a 105° bond angle allowing the oxygen to pull much of the charge away from the two hydrogen atoms.
This creates a highly polar and “sticky” water molecule.
This is why a belly flop hurts as well as water being able to dissolve many different substances

26. Chapter 23 Chemical Bonding

27. Bonding Covalent Compounds
Gases, liquids, or solids (made of molecules)
Low melting and boiling points
Poor electrical conductors in all phases
Many soluble in nonpolar liquids but not in water

28. Bonding Ionic Compounds Crystalline solids (made of ions)
High melting and boiling points
Conduct electricity when melted or in solution
Many soluble in water but not in nonpolar liquid