ionic bonding

Question 1

define an ion

Answer 1

ions = atoms (monatomic ions) or groups of atoms (i.e. polyatomic ions) that have become positively or negatively charged by loosing/gaining valence electrons respectively, to have a stable full (8 e’s) outer shell

Question 2

what is a cation

Answer 2

cations - positively charged → has lost e’s (protons > electrons) e.g. Na +

Question 3

what is an anion

Answer 3

anions - negatively charged → has gained e’s (protons < electrons) e.g. Na +

Question 4

define ionic bonding

Answer 4

• the electrostatic attraction between cations and anions in an ionic substance (lattice)
  
  • involves the transfer of one or more electrons between metal cations (which hv high IE) to non-metal anions (which hv low IE), in order for both atoms to achieve a more stable configuration

Question 5

how is ionic bonding represented

Answer 5

thru electron dot diagrams that only show valence electrons a.k.a Lewis Dot Diagrams

Question 6

describe the structure of an ionic substance

Answer 6

in solid state ionic substances are arranged in orderly 3D lattices - each positive ion and negative ions arranged alternately (held together by electrostatic attraction between opposite charges)

Question 7

explain the following physical property in ionically bonded substances: melting point/boiling point

Answer 7

• high melting/boiling point
  
  • strong electrostatic force of attraction (ionic bond) between oppositely charged ions in ionic solids
  • in solid state ionic compounds exist in rigid lattices - need to overcome many different forces
  • large amounts of energy required to overcome strong ionic bonds in ionic lattice/network
  • therefore high melting point
  • even in liquid state, attractive forces between positive and negative ions are strong → results in high boiling point

Question 8

explain the following physical property in ionically bonded substances: hard/brittle

Answer 8

• the bonding holding the ions in ionic lattice are strong (intramolecular) resulting in hard structure
• when lattice put under pressure (e.g. hit with hammer) layers of ions may be pushed in manner that causes like charges to line up - causing electrostatic repulsion and lattice fall apart → brittle

Question 8

explain the following physical property in ionically bonded substances: conductivity in solid/liquid/aqueous states

Answer 8

• non-conductors of electricity in solid state
  
  • though ions have charge they are not free to move (mobile) in solids state as they’re held together by ionic bonds in fixed positions in rigid lattice, thus cannot carry charge
• can conduct electricity in liquid/aqueous state
  
  • when melted or dissolved in water, ions dissociate - i.e. break away from rigid lattice and are free to move
  • presence of mobile ions allows electric charge to be carried, therefore can conduct electricity

Question 9

define a monatomic ion

Answer 9

A monatomic ion is an ion formed from a single atom.
- negative monatomic ions add suffix -ide e.g. S^2- = sulfide

Question 10

define and explain the bonding in polyatomic ions

Answer 10

A polyatomic ion is an ion composed of two or more atoms.
- net charge applies to all atoms in molecule
- but individual atoms in molecule are covalently bonded to each other
- e.g. sulfate

Question 11

define a salt

Answer 11

salt = substance formed when hydrogen in acids is substituted by a metal ion (ionic compound)

e.g. HCl → NaCl

Question 12

define anhydrous salt

Answer 12

• chemical compounds left behind after water of crystallisation remvoed
  
  • e.g. Heating of Copper sulphate pentahydrate (CuSO4. 5H2O) produce anhydrous copper sulphate(CuSO4)
  • can either be formed from removal of water through dehydration - evaporation of water molecules, through application of heat).
  • when exposed to water, they may absorb or dissolve water molecules, leading to the formation of hydrated salts.

Question 13

define hydrated salts

Answer 13

• chemical compounds that contain water molecules within their crystal structure - referred to as “water of crystallization”
  
  • e.g. Copper sulphate pentahydrate (CuSO4. 5H2O)
  • Hydrated salts are formed when an anhydrous salt absorbs water or when a salt is crystallized from a water-containing solution.

Question 14

outline the differences between hydrated and anhydrous salts

Answer 14

• Anhydrous salts do not contain water molecules in their crystal lattice structure, while hydrated salts do have it
• The physical appearance of hydrated salts may vary due to the presence of water molecules, while anhydrous salts are typically colorless or exhibit the natural color of their constituent ions.
• Hydrated salts can undergo reversible hydration/dehydration reactions, whereas anhydrous salts generally do not exhibit such behavior.

Aspect | Hydrated Salts | Anhydrous Salts |

Question 15

define water of crystallization

Answer 15

water molecules that form an essential part of the crystal structure of some compounds

Question 16

explain the role of water of crystallization

Answer 16

Water of crystallization is the water molecules chemically bound within the crystal lattice of a compound. It stabilizes the crystal structure, affects physical properties like melting point, and contributes to the appearance of crystals. Hydration and dehydration processes are reversible, influencing compound properties and applications. Compounds with water of crystallization can release water when heated, serving as sources of water in certain environments. Analyzing water of crystallization content aids in compound identification and characterization.