Bonding and Molecular orbital theory - valence bond theory

Question 1

wave function and probability explanation

Answer 1

the probability density of an electron within an orbital can be found from squaring the wave function.

Question 2

core atomic orbitals definition

Answer 2

The orbitals which aren’t in the highest electron energy shell containing an electron.

Question 3

valence orbitals

Answer 3

The orbitals in the highest electron energy shell containing an electron.

Question 4

exothermic reaction definition

Answer 4

a reaction which releases heat energy with a negative enthalpy

Question 5

endothermic reaction definition

Answer 5

a reaction which absorbs heat energy with a positive enthalpy

Question 6

bonds breaking in bond enthalpy

Answer 6

requires heat energy to be absorbed, which means endothermic
which means positive enthalpy

Question 7

bonds forming bond enthalpy

Answer 7

requires heat energy to be released, which means exothermic
which means negative enthalpy

Question 8

bond enthalpy calculation

Answer 8

bonds of reactants - bonds of products.

Question 9

enthalpy symbol and unit

Answer 9

ΔH = kJ/mol

Question 10

requirements for valence bond theory

Answer 10

atomic orbitals with ne electron present must overlap.
These overlapping orbitals must have the same sign.

Question 11

covalent bond strength rule

Answer 11

the greater the area of overlap for two atomic orbitals relative to the total area of both orbitals, the greater the covalent bond strength.

Question 12

σ bond definition

Answer 12

a bond formed by the end on overlap of s or p orbitals, which produces a bond with no nodal planes and bond axis symmetry.

Question 13

nodal plane definition

Answer 13

an area within an orbital where there is no probability of finding an electron.

Question 14

orbitals which can form σ bonds

Answer 14

s and p orbitals

Question 15

sign on an s orbital

Answer 15

must always be positive since the wavefunction cannot be negative.

Question 16

π bond definition

Answer 16

A bond formed from the overlap of two p orbitals, containing a nodal plane on the bond axis due to the side on overlap.

Question 17

rule for the sign of a π bond

Answer 17

when you rotate the π bond 180 degrees around the bond axis the sign changes due to the nodal plane.

Question 18

Homonuclear molecules

Answer 18

a molecules which is composed of one type of element.

Question 19

valence bonding for homonuclear molecules

Answer 19

use normal electronic configuration
when 1 p orbital is half filled make a σ bond.
for every p orbital half filled add a π bond.

Question 20

two types of orbital bond theory

Answer 20

normal structure and hybrid structure

Question 21

normal structure

Answer 21

uses normal electronic structure to determine number of bonds formed and bond structure.

Question 22

advantages of normal electronic structure

Answer 22

it will get the energy of all the different types of orbitals correct

Question 23

disadvantages of normal electronic structure

Answer 23

it will get the bond angle and geometry incorrect.

Question 24

hybrid orbital theory

Answer 24

change the electronic structure to suit VSEPR rules, then find the number of bonds based on the new electronic configuration.

Question 25

advantage of hybrid orbital theory

Answer 25

it will accurately predict the bond angles and geometry in a molecule

Question 26

disadvantage of hybrid orbital theory

Answer 26

the energy of orbitals will not necessarily be correct.

Question 27

hybridisation definition

Answer 27

where atomic orbitals of different shapes and energies are mixed to form a set of degenerate orbitals with the same structure.

Question 28

sp3 structure

Answer 28

tetrahedral

Question 29

sp2 structure

Answer 29

trigonal pyramidal with a 2p orbital perpendicular to the hybrid orbitals.

Question 30

sp structure

Answer 30

linear with two 2p orbitals perpendicular to the hybrid orbitals.

Question 31

process of producing hybrid orbital structure

Answer 31

use VSEPR to find arrangement of valence electron pairs.
choose correct hybridisation
make hybrid orbitals degenerate and apply Hund’s rule.
draw out structure.

Question 32

sp3 bond type

Answer 32

single bond
(σ)

Question 33

sp2 bond type

Answer 33

double bond
(σ + π)

Question 34

sp bond type

Answer 34

triple bond
(σ + 2π)

Question 35

how are σ bonds formed in hybridisation

Answer 35

from overlap of hybrid orbitals of the same sign.

Question 36

how are π bonds formed in hybridisation

Answer 36

from overlap of 2p orbitals perpendicular to the hybrid orbitals.

Question 37

rule for atoms with lone pairs and atoms with electron deficiency

Answer 37

atoms which are electron deficient and atoms which have lone pairs can form dative covalent bonds if the unoccupied orbital and the orbital containing the lone pair have the same sign.