1. Mastering Chemistry
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Course ID:
MCWICKUN89304

2. Basic Concepts of Chemical Bonding
Chapter 8

3. What’s Ahead (p 297) Three types of bonds Lewis symbols Ionic bonding
Octet rule
Lattice energy in ionic compounds

4. Three Types of Chemical Bonds
Ionic bond
Transfer of electrons
Between metal and nonmetal ions
Covalent bond
Sharing of pairs of electrons
Between nonmetal atoms
Metallic bond
Bonding electrons relatively free to move

5. Valence electrons: outer shell electrons of an atom; valence electrons participate in chemical bonding.
Group
# of valence e-
e- configuration 1A 1
ns1 2A 2
ns2 3A 3
ns2np1 4A 4
ns2np2 5A 5
ns2np3 6A 6
ns2np4 7A 7
ns2np5

6. Show only valence electrons!
Table 8.1
Show only valence electrons!

7. Ionic Bonding
Na (s) + ½ Cl2 (g) → NaCl (s) ΔHfo = −410.9 kJ

8. The Crystal Structure of Sodium Chloride
Fig 8.3

9. The Ionic Bond - - - Li+ F Li + F 1s22s1 1s22s22p5 [He] 1s2 1s22s22p6
[Ne] Li
Li+ + e-
e- + F -
LiF(s) F -
Li+ +
Li+
Octet Rule: Atoms tend to
gain, lose, or share electrons
until surrounded by 8 valence
electrons

10. Electrostatic (Lattice) Energy
Lattice energy (E): the energy required to completely separate one mole of a solid ionic compound into gaseous ions
Q+ is the charge on the cation
Eel = k
Q+Q- d
Q- is the charge on the anion
d is the distance between the ions
Eqn. [8.4]
Lattice energy (E):
increases as Q increases and/or
increases as d decreases

11. Electron Configurations of Cations and Anions
of Representative Elements
Metal atoms lose electrons so that cation has a noble-gas outer electron configuration
Nonmetal atoms gain electrons so that anion has a noble-gas outer electron configuration

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

13. Electron Configurations of Cations of Transition Metals
When a cation is formed from an atom of a transition metal, electrons are always removed first from the ns orbital and then from the (n – 1)d orbitals.
“First in, first out”
Fe: [Ar]4s23d6
Mn: [Ar]4s23d5
Fe2+: [Ar]4s03d6 or [Ar]3d6
Mn2+: [Ar]4s03d5 or [Ar]3d5
Fe3+: [Ar]4s03d5 or [Ar]3d5

14. Three Types of Chemical Bonds
Ionic bond
Transfer of electrons
Between metal and nonmetal ions
Metallic bond
Bonding electrons relatively free to move
Covalent bond
Sharing of electrons
Between nonmetal atoms

15. Cross Section of a Metallic Crystal
Electron-Sea Model
Metallic Crystals
Lattice points occupied by metal atoms
Held together by metallic bonds
Soft to hard, low to high melting point
Good conductors of heat and electricity
Cross Section of a Metallic Crystal
nucleus &
core e-
mobile “sea”
of valence e-

16. Covalent Bonding Objectives: Characteristic properties
Lewis structures
Multiple bonds
Bond polarity and electronegativity

17. Covalent Bonding Atoms share pairs of electrons
Several electrostatic interactions in these bonds:
Attractions between electrons and nuclei
Repulsions between electrons
Repulsions between nuclei

18. Change in electron density as two hydrogen atoms approach each other

19. Covalent Bond Why should two atoms share electrons? 7e- 7e- 8e- 8e- F+ F
Lewis structure of F2
lone pairs F
single covalent bond
single covalent bond F

20. Lewis structure of water
single covalent bonds H + O + H O H or
Double bond – two atoms share two pairs of electrons O C or O C
double bonds
Triple bond – two atoms share three pairs of electrons N or N
triple bond