5 Electrons and Bonding

Question 1

How many electrons are in the first four shells?

Answer 1

n1 = 2
n2 = 8
n3 = 18
n4 = 32

Question 2

What is a shell?

Answer 2

Shells are regarded as energy levels
The energy increases as the shell number increases
The shell number is called the principle quantum number

Question 3

What is an atomic orbital?

Answer 3

A region around the nucleus that can hold up to two electrons, with opposite spin

Question 4

What are the different types of orbitals?

Answer 4

S, p, d and f orbitals

Question 5

Describe the shape of the s and p orbitals

Answer 5

S: the electron cloud is within the shape of a sphere
P: The electron cloud is within the shape of a dumb-bell

Question 6

How many orbitals are in each shell (n1, n2, n3, n4)? How many electrons are in each orbital?

Answer 6

n1 = 1 s-orbital –> 2
n2 = 3 p-orbitals –> 6
n3 = 5 d-orbitals –> 10
n4 = 7 f-orbitals –> 14

Question 7

How many electrons can an orbital hold?

Answer 7

Two electrons

Question 8

How do the orbitals fill?

Answer 8

Order of increasing energy

Question 9

What is the order of filling orbitals?

Answer 9

1s, 2s, 2p, 3s, 3p, 4s, 3d

Question 10

Why does 4s sub-shell fill before 3d sub shell?

Answer 10

3d sub shell is at a higher energy than the 4s sub shell (therefore 4s fills before 3d as orbitals fill in order of increasing energy)

Question 11

How and why do you draw electrons in the ‘electrons-in-box’ model?

Answer 11

Electrons are negatively charged and repel one another
Electrons have a property called spin - either up or down (shown as an arrow)
Two electrons in an orbital must have opposite spins to counteract the repulsion between the negative charges of the two electrons

Question 12

How are orbitals filled?

Answer 12

For orbital with the same energy, the electrons occupy each orbital singly first in order to minimise repulsion between paired electrons

Question 13

How do ions form regarding electron configuration?

Answer 13

The highest energy sub-shells lose or gain electrons

Question 14

What happens with the 4s shells with ions?

Answer 14

4s sub-shell fills before the 3d sub-shell
4s sub-shell also empties before the 3d sub-shell

Question 15

Define ionic bonding

Answer 15

The electrostatic attraction between positive and negative ions

Question 16

Why does a giant ionic lattice structure form?

Answer 16

Each ion attracts oppositely charged ions in all directions

Question 17

What state are ionic compounds in at room temperature and why?

Answer 17

• Almost all solids at room temperature
• At RT there is insufficient energy to overcome the strong. electrostatic forces of attraction between the oppositely charged ions in the giant ionic lattice

Question 18

Why do ionic compounds have high melting and boiling points?

Answer 18

High temperatures are needed to provide the large quantity of energy needed to overcome the strong electrostatic attraction between the ionic

Question 19

In which cases are melting points higher for certain ionic compounds?

Answer 19

Lattices with ions with greater ionic charges, as there is stronger attraction between ions
Ionic attraction also depends on the size of the ions

Question 20

Describe the patterns of ionic compounds solubility

Answer 20

-Many ionic compounds dissolve in polar solvents e.g. water
-Polar water molecules break down the lattice and surround each ion in solution
-If a compounds is made of ions with large charges, the ionic attraction may be too strong for water to break down the lattice

Question 21

What are the two main processes solubility requires?

Answer 21

-Ionic lattice must be broken down
-Water molecules must attract and surround the ions
Solubility depends of relative strengths of the attractions within the giant ionic lattice and the attraction between ions and water molecules

Question 22

Do ionic compounds conduct electricity as solid and why?

Answer 22

No
The ions are in a fixed position in the giant ionic lattice
There are no mobile charge carriers
Non-conductor

Question 23

Do ionic compounds conduct electricity as a liquid or dissolved in water?

Answer 23

Yes
Solid ionic lattice breaks down
Ions are now free to move as mobile charge carriers

Question 24

Define covalent bonding

Answer 24

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

Question 25

What is the orbital overlap in a covalent bond?

Answer 25

A covalent bond is formed by the overlap of atomic orbitals, each of which contains 1 electron to give a shared pair of electrons

Question 26

What are the 2 main points about the covalent bond itself?

Answer 26

The shared pair of electrons is attracted to the nuclei of both the bonding atoms
The bonded atoms often have outer shells with the same electron structure as the nearest noble gas

Question 27

What is the difference between ionic and covalent interactions?

Answer 27

The attractions in a covalent bond is very localised and hence we can get molecules

Question 28

What is a lone pair?

Answer 28

Paired electrons that are not shared

Question 29

What is a dative bond?

Answer 29

A covalent bond in which the shared pair of electrons has been supplied by one of the bonding atoms only - originally a lone pair

Question 30

What is the average bond enthalpy?

Answer 30

A measurement of covalent bond strength (larger the value of the average bond enthalpy the stronger the covalent bond)