Section A 1

Question 1

So we define a mole (mol) of a substance as containing …. molecules.
This value is …

Answer 1

6.022 x 10^23

Avogadros number, NA (or sometimes L)

Question 2

M(Mg) = 24.31 x 1 g mol-1 = 24.31 g mol-1

This value is called the….. and it … units, in contrast to the relative ….., which ….

Answer 2

molar mass, M
has

molar (atomic) mass, Mr
is unitless

Question 3

Using ….. the mass of the individual isotopes can be determined.

Answer 3

a mass spectrometer

Question 4

Relative atomic mass is used to calculate ….

And the molar mass of a substance, M, is obtained by …..

Answer 4

relative molecular mass, Mr:

e.g. Mr(H2O) = (1.008 x 2) + (15.999 x 1) = 18.015

multiplying Mr by 1 g mol-1

e.g. M (H2O) = 18.015 x 1 g mol-1 = 18.015 g mol-1

This means that if we want to use 1 mol of water in the laboratory we would need 18.015 g.

Question 5

No of mols (mol) =

Answer 5

mass (g) / molar mass (g mol-1)

Question 6

An implication of describing the electron as a wave is the uncertainty principle –

Answer 6

its position and momentum (energy) cannot not simultaneously be determined.

Question 7

Each electron in an atom is labelled with four quantum numbers. The first is….

It tells you about ….

Answer 7

the Principal quantum number:
n (the shell):
n = 1, 2, 3, …

how big the orbital is, or how far (on average) an electron
occupying it is from the nucleus.

Question 8

The second quantum number is ….. :

This tells you about….:

Answer 8

the angular momentum quantum number: l
l = 0, … n-1

the shape of the orbital

l = 0 is an s orbital,
l = 1 is a p orbital,
l = 2 is a d orbital, etc.

Question 9

The third quantum number is …. :

These are … orbitals, and tell you about ….

Answer 9

the magnetic quantum number: ml :

ml = -l, … +l
e.g. if l = 1, ml = -1, 0, +1.

the px, py, and pz

the orientation of the orbital

Question 10

Wavefunctions can be used to calculate the radial distribution function of the orbital i.e. …

Answer 10

how the probability of finding the electron varies with distance from the nucleus.

Question 11

The position where the function equals zero is called a ….and there is zero probability of the electron being found there.

Answer 11

node

Question 12

the Pauli exclusion principle -

Answer 12

A maximum of two electrons can share each orbital, with the same values of n, l, ml but different spin (ms = +1/2 and -1/2).

Question 13

Hunds Rule of maximum multiplicity -

Answer 13

If two or more orbitals have the same energy, then electrons will spread out to occupy the maximum possible number of these, maximising the number of parallel spins.

Question 14

If the electrons occupy separate orbitals then they occupy different regions of space so there is …. electrostatic repulsion. This is a … energy arrangement.

Answer 14

less

lower

Question 15

Why is cobalt essential for vitamin B12 function?

Answer 15

Vitamin B12 has an unusual Co-C bond which
can be broken three ways:
1. To form Co(III) and CH3-
(anion)

2. To form Co(II) and CH3.
   (rodnik)
3. To form Co(I) and CH3+
   (kation)

Essential to its function that Co is stable in three oxidation states and they are relatively close in energy to allow fast conversion between them.

Question 16

Przypomnienie:

Compounds which require more than an octet of electrons in order to draw a Lewis structure are called …..

Answer 16

Ans. hypervalent compounds.

Although period 2 elements obey the octet rule very well,

Period 3 elements begin to show some deviations.
e.g. PCl5 can only be explained if P has 10 electrons in its outer shell
In SF6 S must have 12 electrons in its outer shell

Question 17

Znając: Number of electron pairs around central atom: 2

Podaj:

Shape:
Bond Angles:
Example:

Answer 17

Linear
180
BeF2

Question 18

Znając: Number of electron pairs around central atom: 3

Podaj:

Shape:
Bond Angles:
Example:

Answer 18

Trigonal planar
120
BF3

Question 19

Znając: Number of electron pairs around central atom: 4

Podaj:

Shape:
Bond Angles:
Example:

Answer 19

Tetrahedral
109.5
CF4

Question 20

Znając: Number of electron pairs around central atom: 5

Podaj:

Shape:
Bond Angles:
Example:

Answer 20

Trigonal bipyramidal
90, 120
PF5

Question 21

Znając: Number of electron pairs around central atom: 6

Podaj:

Shape:
Bond Angles:
Example:

Answer 21

Octahedral
90
SF6

Question 22

Znając: Number of electron pairs around central atom: 7

Podaj:

Shape:
Bond Angles:
Example:

Answer 22

Pentagonal bipyramidal
90, 72
IF7

Question 23

Structures based on tetrahedral geometry:

1. No lone pairs
2. One lone pair
3. Two lone pairs

Answer 23

1. Tetrahedral
2. Trigonal pyramidal
3. Bent

Question 24

Structures based on trigonal bipyramidal geometry

1. No lone pairs
2. One lone pair
3. Two lone pairs

Answer 24

1. Trigonal bipyramidal
2. Disphenoidal
3. T-shaped

Question 25

Structures based on octahedral geometry 1. No lone pairs 2. One lone pair 3. Two lone pairs

Answer 25

1. Octahedral 2. Square pyramidal 3. Square planar

Question 26

Bond angles: H20 NH3 CH4 HCN CO2 Acetone SF4

Answer 26

H2O: e = 104.5 'bent' NH3: e = 107.3 'trigonal pyramidal' CH4: e = 109.5 'tetrahedral' bond angle gets smaller due to lone pair repulsion (od dołu do góry) HCN: e = 180 'linear' CO2: e = 180 'linear' Acetone 'Trigonal planar' SF4: The F-S-F angle involving the axial F atoms is 173

Question 27

Limitations of the Lewis model of bonding

Answer 27

It also does not explain some other observations, for example that the oxygen molecule is paramagnetic (it has unpaired electrons), which is not predicted by the Lewis model.

Question 28

ATP is made up from three sections:

Answer 28

A purine base – Adenine A pentose sugar – Ribose A phosphate section - Triphosphate Adenine + Ribose = Adenosine

Question 29

These bonds are called pi or π-bonds. They have two ...., above and below the line between the atoms.

Answer 29

lobes

Question 30

Combinations of waves can either be constructive or destructive. We use this argument when combining the s orbitals to from a bond: If they combine constructively then electron density between the atoms is ...... This is called .... If the s orbitals combine destructively then electron density between the atoms is and this is called ....

Answer 30

increased a bonding molecular orbital. decreased an anti-bonding molecular orbital.

Question 31

Bond Order =

Answer 31

[(number of bonding electrons) – (number of anti-bonding electrons) ] /2

Question 32

Bond order of: 1. He2 2. H2 3. He2 +

Answer 32

1. So for He2: Bond Order = (2 – 2) / 2 = 0 A bond order of zero means there is no bond, so the He2 molecule does not exist. 2. H2 = (2 – 0) / 2 = 1 A bond order of 1 is equivalent to a single bond using the Lewis model, and is consistent with observations. 3. He2 + = (2 – 1) / 2 = ½ A bond order of ½ is something that is not encountered in the Lewis electron pair model, but something that MO theory can predict with ease. What this means is that a bond of about half the strength of a single bond can form between the He atoms of He2+ This means that this molecule can exist, but will not be very stable. Its existence is likely to be transient.

Question 33

Rozwiń skróty: LUMO HOMO

Answer 33

Lowest unoccupied MO (Molecular Orbital) Highest occupied MO