Chapter 5 - Electrons and Bonding

Question 1

What is the shell number called?

Answer 1

The principal quantum number (n)

Question 2

What is an atomic orbital?

Answer 2

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

A region in space where there is a high probability of finding an electron.

Question 3

What are the 4 different types of orbital?

Answer 3

s, p, d and f orbitals.

Question 4

What is the shape of a s orbital and a p orbital?

Answer 4

s orbital - sphere

p orbital - dumbbell

Question 5

What is a sub-shell?

Answer 5

A group of orbitals of the same type.

Question 6

Electrons fill orbitals in order of…

Answer 6

…increasing energy (1s → 4f)

Question 7

Why must the 2 electrons in an orbital have opposite spins?

Answer 7

The opposite spins help to counteract the repulsion between the negative charges of the two electrons.

Question 8

What is ionic bonding?

Answer 8

The electrostatic attraction between positive and negative ions.

Question 9

Why are some ionic compounds insoluble in water?

Answer 9

In a compound made of ions with large charges, the ionic attraction may be too strong for water to be able to break down the lattice structure.

Question 10

Why are some ionic compounds soluble in polar solvents?

Answer 10

The slightly charged atoms of the polar solution can attract the charged ions in within the ionic lattice causing the ionic compound to break and dissolve in the polar solution.

Question 11

What are the properties of ionic compounds?

Answer 11

Most ionic compounds:

• have high melting and boiling points
• tend to dissolve in polar solvents such as water
• conduct electricity ONLY in the liquid state or in aqueous solution as the ions are free to move.

Question 12

What is a covalent bond?

Answer 12

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

The overlap of atomic orbitals, each containing one electron, to give a shared pair of electrons.

Question 13

What is a dative covalent (coordinate) bond?

Answer 13

A covalent bond in which the shared pair of electrons has been supplied by one of the bonding atoms only.

e.g.
NH3 + H+ → NH4

Question 14

What is the number of electrons that can fill the first 4 shells?

Answer 14

1st shell = 2
2nd shell = 8
3rd shell = 18
4th shell = 32

Question 15

What is the number of electrons that can fill s-, p-, d- and f-sub-shells?

Answer 15

s-sub-shell = 1 orbital, 2 electrons
p-sub-shell = 3 orbitals, 6 electrons
d-sub-shell = 5 orbitals, 10 electrons
f-sub-shell = 7 orbitals, 14 electrons

Question 16

For orbitals of the same energy (in the same sub-shell), orbitals are occupied…

Answer 16

…singly before pairing

Question 17

What factors affect the melting point of ionic compounds?

Answer 17

• Size (smaller size → higher mp and bp)
• Charge of ions (higher charge → higher mp and bp)
• Ratio of ions (closer to 1:1 → higher mp and bp)
  e. g. NaCl has higher mp than MgCl2 as larger ratio means negative Cl- ions would have to share/divide electrostatic attraction from positively charged Mg+ ion.

Question 18

What is special about the 4s sub-shell?

Answer 18

The 4s sub-shell has a lower energy than the 3d sub-shell.

So the 4s sub-shell is filled and emptied before the 3d sub-shell.