1. Chemical Bonds

2. WHY DO ELEMENTS BOND?
When atoms are independent and not bonded, they possess __________ potential energy!
Nature wants things to have _______
potential energy
Ex. A boulder on the edge of a cliff has a lot of potential energy – the tendency in nature is for that rock to ________, which causes an _____________ in potential energy and a ________________ in stability!
increased
lower
fall
decrease
Increase

3. Sooooooo, by bonding: 1. Potential Energy Decreases
2. Stability Increases

4. Electronegativity Chart

5. Three Types of Bond Type of Bond Electronegativity Difference Example
Ionic
1.7 and above
Ex. MgO2
Mg – O – 3.5
Difference: 2.3
Covalent Polar
0.3 to 1.6
Ex. CO2
C – O – 3.5
Difference 1.0
Covalent Non-Polar
0.0 to 0.2
Ex. O2
O – O – 3.5
Difference: 0.0

6. IONIC BOND bond formed between two ions by the ________ of electrons
transfer

7. Formation of Ions from Metals
Ionic compounds result when metals react with nonmetals
Metals lose electrons to match the number of valence electrons of their nearest noble gas
Positive ions form when the number of electrons are less than the number of protons
Group 1 metals  ion 1+
Group 2 metals  ion 2+
Group 13 metals  ion 3+

8. Some Typical Ions with Positive Charges (Cations)
Group 1 Group 2 Group 13 H+ Mg2+ Al3+ Li+ Ca2+ Na+ Sr2+ K+ Ba2+

9. Learning Check
A. Number of valence electrons in aluminum 1) 1 e- 2) 2 e- 3) 3 e- B. Change in electrons for octet 1) lose 3e- 2) gain 3 e- 3) gain 5 e- C. Ionic charge of aluminum 1) 3- 2) 5- 3) 3+

10. Solution
A. Number of valence electrons in aluminum 3) 3 e- B. Change in electrons for octet 1) lose 3e- C. Ionic charge of aluminum 3) 3+

11. Learning Check
Give the ionic charge for each of the following: A. 12 p+ and 10 e- 1) 0 2) 2+ 3) 2- B. 50p+ and 46 e- 1) 2+ 2) 4+ 3) 4- C. 15 p+ and 18e- 2) 3+ 2) 3- 3) 5-

12. Ions from Nonmetal Ions
In ionic compounds, nonmetals in 15, 16, and 17 gain electrons from metals
Nonmetal add electrons to achieve the octet arrangement
Nonmetal ionic charge:
3-, 2-, or 1-

13. Ionic Bond
Between atoms of metals and nonmetals with very different electronegativity
Bond formed by transfer of electrons
Produce charged ions all states. Conductors and have high melting point.
Examples; NaCl, CaCl2, K2O

15. Ionic Bonds: One Big Greedy Thief Dog!

17. COVALENT BOND bond formed by the ________ of electrons
sharing

18. Covalent Bond
Between nonmetallic elements of similar electronegativity.
Formed by sharing electron pairs
Stable non-ionizing particles, they are not conductors at any state
Examples; O2, CO2, C2H6, H2O, SiC

19. Covalent Bonds

20. Bonds in all the polyatomic ions and diatomics are all covalent bonds

21. when electrons are shared _______
NONPOLAR COVALENT BONDS
when electrons are shared _______
equally
H2 or Cl2

22. There are 7 Diatomics – all are Non-polar:
Cl2
Br2 O2 F2 N2 I2 H2

23. 2. Covalent bonds- Two atoms share one or more pairs of outer-shell electrons.
Oxygen Atom
Oxygen Atom
Oxygen Molecule (O2)

24. when electrons are shared but shared _______
POLAR COVALENT BONDS
when electrons are shared but shared _______
unequally
H2O

25. Polar Covalent Bonds: Unevenly matched, but willing to share.

26. - water is a polar molecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.