Electrons and bonding

Question 1

What happens to the energy as the number of shells increases?

Answer 1

Energy increases

Question 2

What are shells made up of?

Answer 2

Atomic orbitals

Question 3

Define atomic orbital

Answer 3

A region around the nucleus that can hold up to 2 electrons, with opposite spins

Question 4

What shape is an s-orbital?

Answer 4

Spherical

Question 5

What shape is a p-orbital?

Answer 5

Dumb-bell

Question 6

Define sub-shells

Answer 6

A group of orbitals of the same type within a shell

Question 7

What are the rules for the filling of orbitals?

Answer 7

• Orbitals fill in order of increasing energy ( 3d sub-shell is at a higher energy than the 4s sub-shell so the 4s sub-shell fills before the 3d sub-shell )
• Electrons pair with opposite spins to help to counteract the repulsion between the negative charges of the 2 electrons
• Orbitals with the same energy are occupied singly first so one electron occupies each orbital before pairing starts to prevent repulsion

Question 8

Why are silicon, carbon and chlorine all classified as p-block elements?

Answer 8

They have their highest energy electron in a p-orbital

Question 9

What is special about the 4s sub-shell?

Answer 9

• The 4s sub-shell is at a lower energy than the 3d sub-shell
• So the 4s sub-shell fills before the 3d sub-shell and also empties before the 3d sub-shell

Question 10

When do ionic bonds occur?

Answer 10

When a metal and non-metal react to form a compound

Question 11

Define ionic bond

Answer 11

The electrostatic attraction between positive and negative ions

Question 12

What is the structure of ionic compounds?

Answer 12

The ions in an ionic compound form a repeating 3D structure called a giant ionic lattice. Each ion is surrounded by ions of opposite charges

Question 13

Do ionic compounds have high or low melting / boiling points? Explain your answer

Answer 13

• Ionic compounds have high melting and boiling points as a large amount of energy is required to break all the strong ionic bonds in the giant ionic lattice
• The melting points are higher for lattices containing ions with greater ionic charges, as there is stronger attraction between ions

Question 14

What state do ionic compounds exist in at room temperature?

Answer 14

Solid

Question 15

Explain the solubility of ionic compounds

Answer 15

• Soluble in polar solvents, such as water, as the polar molecules break down the lattice an surround each ion in solution
• Insoluble in non-polar solvents

Question 16

Do ionic compounds conduct electricity?

Answer 16

• In the solid state, an ionic compound does not conduct electricity as the ions are in fixed positions in the giant ionic lattice and so there are no mobile charge carriers
• When molten or dissolved in water, ionic compounds do conduct electricity as the giant ionic lattice is broken down and the ions are now free to move as mobile charge carriers

Question 17

Define covalent bonding

Answer 17

• The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
• A covalent bond is the overlap of atomic orbitals

Question 18

Where do covalent bonds occur?

Answer 18

Between non-metal atoms

Question 19

What is a dative covalent bond?

Answer 19

A shared pair of electrons in which both bonded electrons are contributed by one of the atoms in the bond

Question 20

What is a lone pair of electrons?

Answer 20

An outer shell pair of electrons that is not involved in bonding

Question 21

What is the difference between ionic bonding and covalent bonding?

Answer 21

In ionic bonding, electrons are transferred and in covalent bonding, electrons are shared

Question 22

Why are elements in period 3 able to have more than 8 electrons in their outer shell?

Answer 22

Because they have access to the d sub-shell