8/9/10

Question 1

why do atoms share e- in covalent bonds

Answer 1

to form more energetically favourable structures

Question 2

filling of valence shells allows atoms to obey the

Answer 2

octet rule
ns2 np6 obeys the octet rule

Question 3

non bonding e- are

Answer 3

lone pairs
this is when s valence e- dont have the correct symmetry to react with px py valence electrons
( s and pz can) so px and py are non bonding

Question 4

2nd period Li to Ne never have what

Answer 4

never have more than 8 e- in valence shell
they can be e- poor tho

Question 5

elements that break the octet rule and have more than 8e- in their outer shell are called
(expanded octets)

Answer 5

hypervalent!!!!
period 3 and onwards <3
the molecule it forms and the element itself is called hypervalent.

Question 6

formal charge equation

Answer 6

diff between valence e- in a free atom and e- it has in a lewis structure

valence - number of bonds - number of unshared electrons

Question 7

most likely structure arrangement of atoms in a covalent bond is the one withhh

Answer 7

the lowest formal charge

Question 8

valence shell electron repulsion theory isss

Answer 8

how valence electrons help us predict the shapes of a molecule

Question 9

what are assumptions of the valence shell electron pair repulsion theory

Answer 9

• bonding pairs (e- pairs that hold atoms together)
• lone pairs ( e- pairs that arent involved in a bond)
• e- pairs are - and so repel eachother. e- pairs are as spaced out as possible.

Question 10

finding the shape of a structure

Answer 10

identify central atom (use formal charge if smt)
calculate the number of e- pairs around it (draw the lewis structure)
see if these are all bonding e- pairs.

Question 11

why is the repulsion from a lone pair greater than a bonding pair

Answer 11

its closer to the central atom which allows it to take up more space

Question 12

if u get a shape with a charge outside a [box] what does this mean

Answer 12

• sign: add that number of e- to the central atom

+ sign: take away that number from the central atom

Question 13

what is special about the trigonal bipyramidal structure

Answer 13

the central atom has 2 axial atoms and 2 equitorial atoms

these are in 2 different environments

Question 14

5 e- pairs gives what shape

Answer 14

trigonal bipyramidal
even if one of them is a lone pair

Question 15

where does the lone pair go on a trigonal bipyramidal

Answer 15

It goes on the equitoral position as there are less groups 90* to it.

lone pairs repel more

disphenoidal geometry // sawhorse geometry

it will repel/bend the axial and equitorial slightly from their ‘ideal’ positions.
180* and 120* –> 173. 102

Question 16

what repulsion do we want to stay away from most in trigonal bipyramidal geometry

Answer 16

the 90*
we try put the lone pairs on equitorial positions in order to minimise the 90* repulsions.

2 x 90
3 x 120
with 2 lone pairs this is called the t position, T turned 90* anticlock

Question 17

what does a double bond consist of

Answer 17

1 sigma
1 double

Question 18

in POCl there are 3 single bonds and 1 double bond, what is the shape of this and are there any alterations

Answer 18

4 electron domains
tetrahedral shape
double bond = more electrons than usual so it repels the other bonds more.
tetrahedral but a bit more distorted.

Question 19

if there is a compound with a charge but is bonded with double/triple bonds, the charges are usually where?

Answer 19

on the outer atoms

Question 20

when does the VSEPR not work

Answer 20

• d block elements (shape is based on the nergy and occupation of the d orbitals)

Question 21

VSEPR theory allows us to do what

Answer 21

predict the shapes of a molecule

Question 22

molecules with no lone pairs are

Answer 22

non polar
dipoles cancel out
0 dipole moments

Question 23

molecules with 1 lone pair

Answer 23

polar
dipoles cannot cancel out completely

Question 24

molecules with 2 lone pairs

Answer 24

if its polar or not depends on where the lone pairs are
if theyre 180*, the molecule is non polar

if theyre less than 180* apart, theyre polar

Question 25

what shape does sp3 give

Answer 25

tetrahedral

Question 26

what shape does sp2 give

Answer 26

trigonal planar

Question 27

what p orbital doesnt hybridise for sp2

Answer 27

z

Question 28

what orbital doesnt hybridise for sp

Answer 28

px py

Question 29

why cant period 2 be hypervalent

Answer 29

atom is too small, there would be too much repulsion
unfavourable

extra e- would have to go to empty orbitals however these are too high in energy to be occupied by elements in group2.

Question 30

how can period 3 elements be hypervalent

Answer 30

larger elements
not much replusion
empty/ unoccupied orbitals that can be accessed