1. Bonding

2. Why do elements bond? Bonding results in greater stability
Through sharing electrons- covalent
Through transfer of electrons- ionic
Compounds have different properties than elements
Sodium Chloride vs. Sodium and Chlorine

3. Why do elements bond?
Ex. Sodium is a soft, slivery metal that combines with chlorine, a greenish-yellow gas, to form sodium chloride which is a white crystalline solid
Hydrogen is a flammable gas that combines with oxygen, another gas, to form water, a liquid

4. Bonding & Stability
Octet Rule- elements will bond to reach a stable number of valence electrons- 8
Exceptions:
H, He, Li, Be, B stable with 2
S and P often have more than 8
Period 3 and beyond sometimes have more than 8
Noble gases don’t form compounds because they have 8 valence electrons already
They are stable alone

5. Covalent Bonds Covalent Bonds- sharing of electrons to become stable
Results in a molecule- 2 or more atoms covalently bonded
Occurs between 2 nonmetals
Have relatively low melting points so often liquid or gas at room temperature
No ions, so do not conduct if dissolved in water
Single Covalent bond- sharing of 2 electrons
Longest and weakest of the 3 covalent bonds
Double Covalent bond- sharing of 4 electrons
Triple Covalent bond- sharing of 6 electrons
Shortest and strongest

6. Covalent Bonds

7. Covalent Bonds

8. Covalent Bonds

9. Covalent Bonds

10. Covalent Bonds- Polarity
Atoms may share electrons equally- nonpolar covalent
Atoms have no partial charges
Molecules that are nonpolar have weak attractions for each other (called London Dispersion Forces)
Electronegativity difference of 0.4 or less
Atoms may share electrons unequally- polar covalent
Atoms have partial charges
Molecules that are polar have a stronger attraction for each other (called Dipole-Dipole forces)
Electronegativity difference of over 0.4 within a covalent bond

11. Polar vs. Nonpolar

12. Chemical Formulas
Chemical formula- used to tell us how many of each element are in a compound
Consists of element symbols and subscripts
Water has 2 hydrogen atoms and 1 oxygen atom

13. Chemical Formulas SiO2 silicon- 1 Oxygen-2 C12H22O11
Carbon- 12 Hydrogen-22 Oxygen-11
N2O
Nitrogen- 2 Oxygen-1

14. Writing Lewis Dot Structures for covalent compounds
Count up total number of valence electrons
Determine the central atom
C is often the central atom
For now, the single atom will be the central atom
Bond atoms to satisfy the octet rule first
Fill in valence electrons
If all atoms are not stable, you’ll need to try double or triple bonds
If you have extra electrons, put them on the central atom
For more detailed rules:

15. STOP HERE TO PRACTICE

16. Ionic Compounds Ionic compound - composed of cations and anions
Metal (cation) & nonmetal (anion) OR metal & polyatomic ion
Polyatomic Ions- groups of atoms that are covalently bonded and collectively have a charge
Examples of polyatomic ions: SO42- PO43-

17. Ionic Compounds Ionic compound - composed of cations and anions
Metal (cation) & nonmetal (anion) OR metal & polyatomic ion
Neutral overall
Total positive charge = total negative charge
Solid crystals at room temperature
Melt only at very high temperatures
Ionic Bond: The electrostatic forces that hold ions together in ionic compounds

18. Properties of Ionic Compounds
7.2
Properties of Ionic Compounds
The orderly arrangement of component ions produces the beauty of crystalline solids.
The beauty of crystalline solids, such as these, comes from the orderly arrangement of their component ions.

19. Ionic Bond Formation

20. Sodium Chlorine Sodium Chloride
CLICK FOR ANIMATION OF IONIC and COVALENT BONDING

21. Compare and Contrast Ionic and Covalent Bonding
High melting point
Low melting point
Brittle solids at room temp.
Often liquids or gases at room temp
Combination of metal and nonmetal
Combination of 2 nonmetals
Smallest unit: Formula unit (ratio of ions)
Smallest unit: Molecule
Named without prefixes
Named using prefixes
2 elements always have the same structure
2 elements can often bond in several ways
Conduct when melted or dissolved
Not conductive at all