Supplementary Lecture 1

Question 1

what does quantum mechanics inform us in terms of electrons?

Answer 1

quantum mechanics informs us that small particles such as electrons have wave-like properties

Question 2

Heisenberg Uncertainty Principle:

Answer 2

means the exact position of an electron cannot be specified; only the probability that it occupies a certain region of space

Question 3

atomic orbital:

Answer 3

mathematical description of the wave properties of an electron

Question 4

higher principle quantum number:

Answer 4

higher energy and more nodes

Question 5

valence shell:

Answer 5

the outermost shell of electrons in an atom is its valence shell

Question 6

fully occupied valence shells in periods beyond the first contain…

Answer 6

… 8 electrons

Question 7

octet rule:

Answer 7

the tendency of atoms to form ions with the noble-gas configuration

Question 8

the number of valence electrons =

Answer 8

the elements group number

Question 9

what is the energy like in an atomic orbital?

Answer 9

an atomic orbital has a discrete quantized energy

Question 10

what is each orbital characterised by?

Answer 10

each orbital is characterised by a 3D region of space in which the electron is probably going to be found

Question 11

what is shape described by?

Answer 11

shape is described by orbital sublevel (s, ,p etc)

Question 12

multiple orbitals of same type have the same shape and energy but…

Answer 12

… differ in direction

Question 13

what do larger higher energy atomic orbitals have?

Answer 13

nodes

Question 14

the higher the energy of an a-orbital…

Answer 14

… the more nodes

Question 15

how do all valence electrons exist in covalent compounds?

Answer 15

all valence electrons from atoms in covalent compounds surround all of the nuclei and are delocalised

Question 16

how many bonds can the following atoms make; hydrogen, carbon, nitrogen & oxygen

Answer 16

hydrogen = 1 bonds
carbon = 4 bonds
nitrogen = 3 bonds
oxygen = 2 bonds

Question 17

formal charge =

Answer 17

valence number - no. of electron lone pairs - no. of bonds

Question 18

formal charge of nitrogen when possessing the following number of bonds; 2 bonds, 3 bonds & 4 bonds

Answer 18

2 bonds = -1
3 bonds = 0
4 bonds = +1

Question 19

formal charge of oxygen when possessing the following number of bonds; 1 bonds, 2 bonds & 3 bonds

Answer 19

1 bond = -1
2 bonds = 0
3 bonds = +1

Question 20

how can you find out the formal charge of an atom in a compound?

Answer 20

count all non-bonding valence electrons and half of the bonding electrons

Question 21

why might the lewis structure of a compound not be an accurate depiction and how can it be made accurate?

Answer 21

this is as lewes structures do not represent the polarisation of electron density, to fix this one can add partial charges or draw resonance structures

Question 22

when are resonance structures used?

Answer 22

resonance structures are used when a lewis structure does not accurately represent the bonding and electron delocalisation

Question 23

bonding orbitals from 1s-1s and 2s-2s interactions are…

Answer 23

…cylindrically symmetrical

Question 24

what are σ (sigma) bonds and how are they made?

Answer 24

sigma bonds are bonding orbitals with cylindrical symmetry, they can be made by combining s or p orbitals

Question 25

hybridisation:

Answer 25

a model and not an observable truth. We use it to rationalize structure and chemical behaviour. Molecular orbital theory is the more advanced model.

Question 26

what happens to the orbitals of atoms once they join a compound?

Answer 26

upon joining a compound the atomic orbitals will hybridise into molecular orbitals

Question 27

what shape do molecular orbitals have?

Answer 27

these molecular orbitals have shapes that resemble the atomic orbitals

Question 28

hybridisation:

Answer 28

the concept of mixing atomic orbitals to form new hybrid orbitals

Question 29

Molecular structure is revealed by knowing a molecule’s:

Answer 29

constitution and molecular geometry

Question 30

what is each orbital characterised by?

Answer 30

each orbital is characterised by a 3D region of space in which the electron is probably going to be found

Question 31

how do all electrons behave in the valence shell of covalent compounds?

Answer 31

all valence shell electrons from atoms in covalent compounds surround all of the nuclei and are delocalised

Question 32

what causes a polar covalent bond?

Answer 32

polar covalent bonds are caused by two atoms with highly differing electronegativity

Question 33

what does dipole moment (m) depend on?

Answer 33

Dipole Moment (m) depends on charge separation and distance

Question 34

why are lewis structures bad and how can we fix their problems?

Answer 34

lewis structures are bad because they are a gross simplification, not taking into account molecular shape and partial charges - something that can be fixed with resonance structures (partial charges etc)

Question 35

what does resonance allow us to improve our understanding of?

Answer 35

resonance will allow us to enhance out understanding of bonding