P-block Flashcards
How long must an element exist to be considered discovered
10 femtoseconds aka 10^-14s
Ionisation energy definition
The energy required to remove completely an electron from the gaseous atom or molecule in its ‘ground state’
Electron affinity def
The energy released when a gaseous atom, molecule or ion in its ‘ground state’ gains an electron
Electronegativity (χ) def
The ability of an atom to attract electron density towards itself in a molecule
What happens to bond strength if covalent + polar
Increased electrostatic/Coulombic attraction -> higher than expected bond strength
Highest electronegativity out of sp or sp3
sp as it has more s character so electrons held more tightly
Axes on Ketelaars triangle
Ionicity parameter: Difference in elec - (y ax). Covalency parameter: Average elec of 2 atoms
For an electron in p or s, how much do other electrons contribute to shielding according to Slater’s rules
Same ns, np, nd: 0.35 per e-. (n-1): 0.85 per e-. (n-2) or lower: s=1 (cancels out proton charge)
For an electron in d or f, how much do other electrons contribute to shielding according to Slater’s rules
If its also nd or nf: 0.35 per e. Anything else: s=1
In slaters rules: What if considering a 3d e-, are the 4s e- taken into account for sheilding?
No, higher groups are not considered
What is most electronegative out of sp and sp3
sp
What do Slater’s rules not take into account
Distance from nucleus or penetration
What is an alternative to work out effective nuclear charge other than slaters rules + its problem
Clementi-Raimondi explanation but all values for each orbital in atom must be looked up individually
How does radii vary with coordination number
More ligands means more e- density on metal -> increases apparent size
What happens to s-p separation down a group
It decreases bc they are further form the nucleus so s is not drastically more stable anymore
Why is the s-p separation in Ga and Ge higher than expected
10 extra protons from d block but f block not very shielding. Higher effective nuclear charge pulling in electrons -> more stabilised
What happens to s and p energies across a period
They decrease but s decreases more bc it is closer to nucleus (called better penetration)
Why does sigma and pi levels swap from N2 to O2?
S-p mixing: The gap between s and p gets too big for sp-mixing in oxygen so sigma becomes the lowest level
Trend of promotion energies down a group. Also what happens to other electrons that do not get promoted?
Increases w d-block exception for Ga + Ge. More energy required to promote e- from s to p. They have less electrostatic repulsion.
What is the ‘Inert Pair’ effect
The tendency of electrons in the outermost atomic s orbital to remain unionised or
unshared in compounds of the Group 13-16 elements.
OR
The observation that as a group is descended, the n-2 oxidation state becomes more
favoured (where n = group oxidation state)
Aka group 13 gets 3-2 = +1 oxidation state
One reason for inert pair effect
Covalent bond strength decreases down group bc poor orbital overlap. Therefore, bond enthalpy not enough for rehybridisation energy cost
Why is PbH4 not favourable but CH4 is
CH bonds are strong + promotion energy low -> promotes electron then hybridises (sp3) easier than weak Pb-H bonds + high promotion energy
What is the relativistic effect
Objects near speed of light gain mass. The heavier the element, the faster outer electrons go.
What is the theory of special relativity equatioin
m = m0 / sqrt (1 - (v/c)^2 ) where m0 = electron rest mass