1. Coulomb’s Law
Chemical Bonding

2. A. Coulomb’s Law Formula
E ∝ Q1Q2 r
E= energy of attraction/repulsion between charged particles
Q1= charge of first particle
Q2=charge of second particle
r=distance between particles

3. A. Coulomb’s Law Formula
What it means:
The greater the charge…
…the greater the attraction of opposite charges
…the greater the repulsion of like charges
The closer the particles are to each other, the greater the attraction/repulsion
Charge beats size just like rock beats scissors! ;-)

4. B. Ionization Energy I.E.-energy required to remove an electron
Stronger attraction between nucleus and electron=harder to remove
Q1=charge of an electron
Q2=effective nuclear charge
Nucleus is shielded by inner electrons
Effective nuclear charge increases across a period
r=distance
Approximate using the period (row)

5. B. Ionization Energy Why does Na have higher i.e. than K?
For K r=4 and for Na r=3, Q1 and Q2 are the same (same column), so…
…i.e. is lower for K
More shielding/larger size
Lower energy means less attraction
Easier to remove an electron
More metallic (ability to remove e-)
This also explains why K is bigger than Na

6. B. Ionization Energy Na has lower i.e. than Al…
Same Q1, same r (energy level)
Q2 is 3 for Al and 1 for Na
E is higher for Al
Greater attraction
Holds on to e- more
Al is also smaller as greater nuclear charge pulls energy levels in closer

7. C. Lattice Energy and Bonding
E=Lattice Energy: energy required to separate oppositely charged ions
Higher lattice energy=stronger bond
Q1=charge of first ion
Q2=charge of second ion
r=bond length: distance between nuclei
Can approximate using period of element that is isoelectronic with that ion

8. C. Lattice Energy and Bonding
Isoelec…WHAT??
Isoelectronic—have equal number of electrons
Example:
Na has 11 electrons in 3 energy levels. When it loses a valence electron it now has 10 electrons in 2 energy levels…just like Neon!
Fluorine has 9 electrons in 2 energy levels, it gains one electron and is also isoelectronic with Ne!
Also affects size: cations are smaller, anions larger
Ion with most protons is smallest

9. C. Lattice Energy and Bonding

10. C. Lattice Energy and Bonding
Which has a stronger bond: NaCl or KCl?
NaCl
Na has stronger lattice energy so it has a stronger bond
Na+ has electrons in 2 energy levels, which is less than K+ (isoelectronic with Ar, e- in 3 energy levels)

11. C. Lattice Energy and Bonding
Which has a stronger bond: NaCl or AlCl3?
AlCl3
Al and Na have same number of energy levels (isoelectronic with Ne)
Cl is 1- for both compounds
Al has 3+ charge while Na has 1+ charge
Greater charge = more attraction

12. When an ionic compound in water, the ions dissociate
D. Solubility
When an ionic compound in water, the ions dissociate
Ions are pulled away from each other
A compound with a high lattice energy (stronger bond) will be less soluble than a compound with low lattice energy (weaker bond)

13. Which is more soluble in 80C water: KCl or NaCl?
D. Solubility
Which is more soluble in 80C water: KCl or NaCl?
KCl—has lower lattice energy than NaCl
Which is more soluble in 80C water: NaCl or AlCl3?
NaCl—has lower lattice energy than AlCl3