Electrons, Bonding and Structure & Shapes Of Molecules And Ions

Question 1

Explain why ionic compounds have high melting and boiling points (2)

Answer 1

• Strong electrostatic attractions between oppositely charged ions.
• High temperature needed to provide sufficient energy to overcome the attractions.

Question 2

Explain why ionic compounds dissolve in water (2)

Answer 2

• Polar water molecules are attracted towards ions on the surface of the ionic lattice. Water molecules bond to the ions, weakening and breaking them.
• Ions become surrounded by water molecules and break free from the lattice

Question 3

Define: covalent bonding

Answer 3

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

Question 4

Define: orbital

Answer 4

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

Question 5

Define: isoelectronic

Answer 5

The same number of electrons

Question 6

State the maximum number of electrons that can be held in each of the first three shells of an atom. (3)

Answer 6

1st = 2
2nd = 8
3rd = 18

Question 7

State how many orbitals there are in a p-subshell and how the electrons are arranged if the subshell is full (3)

Answer 7

• 3 atomic orbitals
• each orbital has 2 electrons
• with opposite spins

Question 8

Explain why both G1 & G2 are known as s-block elements (1)

Answer 8

The outer electrons are s-subshell electrons for all

Question 9

Explain the strength of the ionic bond in sodium chloride (2)

Answer 9

• strong electrostatic attraction
• b/w Na+ and Cl- ions

Question 10

Explain why it’s easier to use aqueous MgF2 in a lab setting than the molten version (2)

Answer 10

• High melting point
• as strong electrostatic attraction b/w oppositely charged ions in all directions

Question 11

Compare the binding in phosphorus trichloride and ammonia (4)

Answer 11

• both undergo covalent bonding
• phosphorus Atom and nitrogen atom are both central atoms
• each have 1 lone pair
• 3 shared pairs of electrons

Question 12

Describe how the shape of the periodic table is linked to the electronic structure (6)

Answer 12

• elements in same period have same number of filled shells
• elements in same group have same number of valence electrons
• s-block includes G1 & G2 as it takes only 2 electrons to completely fill s-subshell
• p-block includes G3-0 as it takes 6 electrons to completely fill the p-subshell
• d-Block includes transition metals as it takes 10 electrons to completely fill d-subshell
• d-block begins on period 4 as d-orbitals have higher energy than 4s orbitals

Question 13

Suggest why there are three possible p-subshells but only one possible s-subshell in an atom (3)

Answer 13

• s-orbitals are spherical so multiple subshells not possible
• p-orbitals are propeller shaped so 3 p-orbitals would not overlap significantly

Question 14

Justify why hydrogen is positioned in the middle of the periodic table and not apart of G1 (3)

Answer 14

• very diff physical properties to G1 metals
• and chemical properties
• despite outer shell containing 1 s-subshell electron only

Question 15

Explain why giant ionic structures have high melting points (2)

Answer 15

• strong electrostatic attraction between oppositely charged ions
• large amounts of energy required to overcome them

Question 16

Explain why sodium bromide has a higher melting point than sodium and sodium iodide (6)

Answer 16

Stage 1:
- Na has metallic bonding & a giant structure
- there’s attraction b/w positive nucleus and delocalised electrons in Na

Stage 2:
- ionic bonding in NaBr & giant structure
- there’s attraction b/w + and - ions in NaBr

Stage 3:
- ionic bonds are stronger than metallic bonds
- stronger attraction b/w the + and - ions in NaBr than NaI
- since Br- ion is smaller than I- ion

Question 17

Why is an arrow used to represent a
N ➡️ H bond? (1)

Answer 17

To show both electrons come from nitrogen

Question 18

Suggest how methanol and methanethiol could be separated (1)

Answer 18

(Fractional) distillation

Question 19

Define: ionic lattice (2)

Answer 19

• Repeating pattern
• of oppositely charged ions

Question 20

State whether the following conduct electricity when solid or molten: (5)

• aluminium
• aluminium fluoride
• boron tribromide

Answer 20

Aluminium:
- conducts in solid and molten stated
- has delocalised electrons

Aluminium flouride:
- conducts when molten because it has mobile ions
- doesn’t conduct when solid (ions fixed in position in an ionic lattice)

Boron tribromide:
- does not conduct in solid and molten states (no mobile ions)

Question 21

Explain how the structure and bonding in bromine account for its relatively low melting point (3)

Answer 21

• forces b/w molecules
• which are induced dipole-dipole forces
• are weak so overcome easily by increased kinetic energy

Question 22

Predict the type of structure and bonding of SO2 and MgO & explain the difference in their melting points (4)

Answer 22

• MgO = giant ionic
• SO2 = simple molecule
• ionic bonds in MgO much stronger than intermolecular bonds in SO2
• ionic bonds in MgO require more energy to overcome

Question 23

Describe the relative energies of the 2s orbitals and each of the three 2p orbitals in a nitrogen atom (2)

Answer 23

• p-orbitals have greater energy than
  s-orbitals
• three p-orbitals have equal energy

Question 24

What are the 3 rules for filling electron orbitals? (3)

Answer 24

• Hund’s rule (each orbital must be singlely occupied before being paired up)
• Each orbital can hold up to 2 electrons with opposite spins
• Lowest energy orbitals must be filled first

Question 25

Why is hyrogen H+

Answer 25

fills 1s orbital