Lecture 10

Question 1

metallic bonding

Answer 1

valence electrons far away from the nucleus, not held tightly
multiple atoms overlap without nuclei repelling
doesn’t require close overlap
electrons are delocalised over a sea of nuclei, conduct electricity

Question 2

bond energy

Answer 2

the energy needed to break the bond

Question 3

hydrogen bonding

Answer 3

oxygen is electronegative, O-H bond is polarised
dipole is formed
other dipoles interact to form H bonds

Question 4

kevlar

Answer 4

strong H bonded polymer

Question 5

van der waals

Answer 5

low bond energy
polarisation of an electron cloud by an adjacent nucleus
weak electrostatic induction
but many weak interactions can be strong

Question 6

shielding

Answer 6

core electrons repel the valence electrons
act as a shield to prevent the outer electrons to feel the full charge of the nucleus

Question 7

Zeff

Answer 7

effective nuclear charge
Zeff = Z-S
shape of orbitals affect S
repulsion between valence electrons affect S

Question 8

S and Z

Answer 8

S =core electrons
Z = nuclear charge

Question 9

example of Zeff

Answer 9

check notes

Question 10

atomic radius

Answer 10

as Zeff increases, the electrons are held more tightly into the nucleus
atomic radii decreases across a period, increases down a group

Question 11

ionisation energy (kj/mol)

Answer 11

removing an electron from an atom requires energy
electrons in outer shell are held less stronger than core electrons
as Zeff increases, attraction increases, ionisation energy increases
ionisation energy decreases down a group, radius increases and attraction decreases

Question 12

electron affinity (kj/mol)

Answer 12

adding electrons to an atom releases energy
increases across a period