2.4 - Electrons, Bonding & Structure

Question 1

what is the term used to number the energy levels of shells

Answer 1

Principal quantum numbers (n)

Question 2

how many electrons can shell hold (1-4)

Answer 2

n = 1 : up to 2 electrons
n = 2 : up to 8 electrons
n = 3 : up to 18 electrons
n = 4 : up to 32 electrons

Question 3

What are the 4 subshells

Answer 3

S
P
D
F

Question 4

What is an atomic orbital

Answer 4

a region around the nucleus that can hold up to two electrons, with opposite spins

Question 5

How many orbitals does each subshell have (1-4)
How many electrons can each subshell hold (1-4)

Answer 5

s : one orbital (1 x 2 = total of 2 electrons)
p : three orbitals ( 3 x 2 = total of 6 electrons)
d : five orbitals (5 x 2 = total of 10 electrons)
f : seven orbitals (7 x 2 = total of 14 electrons)

Question 6

What is the shape of a s orbital

Answer 6

Spherical in shape

Question 7

What happens to the size of an orbital as the subshell it is in increases

Answer 7

it gets bigger

Question 8

what is the shape of a p orbital

Answer 8

a dumbbell shape

Question 9

How are orbitals filled

Answer 9

electrons will occupy separate orbitals in the same subshell first to minimise their repulsion and have their spin in the same direction
They will then pair up, with a second electron being added to the first p orbital, with its spin in the opposite direction

Question 10

What is the order of subshells in terms of increasing energy level

Answer 10

1S 2S 2P 3S 3P 4S 3D 4P …..

Question 11

What is Ionic bonding

Answer 11

the electrostatic attraction between positive and negative ions

Question 12

How are ionic compounds arranged

Answer 12

Giant ionic lattices

Question 13

Why are giant ionic lattices formed

Answer 13

as oppositely charged ions act strongly in all directions

Question 14

Explain the melting and boiling point of compounds in a giant ionic lattice

Answer 14

Most are solid at RT as there isn’t enough energy to overcome the strong electrostatic forces of attraction between the oppositely charged ions
Therefore they have a high MP and BP
Also MP and BP are higher for ions with a greater charge eg 2+ and 2-

Question 15

Explain the solubility of compounds in a giant ionic lattice

Answer 15

Many ionic compounds will dissolve in polar solvents as Polar molecules, such as water, can break down or disrupt the ionic lattice and surround each ion in solution:
-The δ+ end of the polar molecule can surround the negative anion
- The δ- end of the polar molecule can surround the positive cation

The solubility of an ionic compound depends on the relative strength of the electrostatic forces of attraction within the ionic lattice and the attractions between the ions and the polar molecule
In general, the greater the ionic charge the less soluble an ionic compound is\

Question 16

Explain the electrical conductivity of compounds in a giant ionic lattice

Answer 16

Ionic compounds do not conduct electricity when solid - This is because the ions are in fixed positions within the solid lattice so there are no mobile charge carriers
Ionic compounds can conduct electricity when they are molten or aqueous - This is because the ions are no longer in fixed positions as the lattice has broken down, therefore, the ions are free to act as mobile charge carriers

Question 17

What is Covalent bonding

Answer 17

the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

Question 18

What is bond energy

Answer 18

the energy required to break one mole of a particular covalent bond in the gaseous states
Bond energy has units of kJ mol-1

Question 19

what is Average bond enthalpy

Answer 19

a measurement of the strength of a covalent bond
The average bond enthalpy term is the average amount of energy needed to break a specific type of bond, measured over a wide variety of different molecules

Question 20

What is bond length

Answer 20

the internuclear distance of two covalently bonded atoms
It is the distance from the nucleus of one atom to another atom which forms the covalent bond

Question 21

What bond has the shortest bond length

Answer 21

Triple bonds (strongest attraction)

Question 22

what is expanding the octet rule

Answer 22

when a atom can accommodate more or less than 8 electrons in the outer shell

Question 23

what is dative covalent bonding or coordinate bonding

Answer 23

When both electrons which form a covalent bond are from the same atom