chpt 9 chemical bonding

Question 1

Define ionic bond.

Answer 1

ionic bonding is btwn metal and non metal joined tgt by strong electrostatic forces of attraction between oppositely charged ions, forming a giant ionic crystal lattice structure.

Question 2

What are the physical properties of an ionic bond ?

Answer 2

1. high mp bp
   large amt of energy needed to overcome strong FOA btwn oppositely charged ions
   higher diff in charges -> stronger
   smaller size of ions -> stronger
2. conducts electricity in molten and aq states but NOT in solid states
   mobile ions in aq molten state
   ions held in place by giant ionic crystal lattice structure and are immobile in solid
3. hard but brittle
   brittle - large force applied, layers of ion can slide, bringing ions of like charges next to each other, causing them to repel and ionic lattice structure shatters
4. often soluble in water but insoluble in organic solvents

Question 3

What are the physical properties of an ionic bond ?

Answer 3

1. high mp bp
   large amt of energy needed to overcome strong FOA btwn oppositely charged ions
   higher diff in charges -> stronger
   smaller size of ions -> stronger
2. conducts electricity in molten and aq states but NOT in solid states
   mobile ions in aq molten state
   ions held in place by giant ionic crystal lattice structure and are immobile in solid
3. hard but brittle
   brittle - large force applied, layers of ion can slide, bringing ions of like charges next to each other, causing them to repel and ionic lattice structure shatters

Question 4

Define covalent bonding.

Answer 4

1. covalent bond is btwn non metal and non metal
2. covalent bond is the electrostatic FOA btwn shared electrons and two positive nuclei of the atoms

Question 5

What are the structures of covalent substances ?

Answer 5

1. simple molecular
   weak intermolecular FOA btwn molecules strong covalent bond btwn atoms
2. giant molecular
   giant network of atoms held together by strong covalent bonds
   diamond -> hard, strong covalent bonds btwn all atoms
   graphite - soft and slippery, layers of carbon atoms and slide across each other since weak intermolecular FOA can be easily overcome with little force
   silicon dioxide / oxide -> hard, strong covalent bonds

Question 6

Define metallic bonding.

Answer 6

1. metallic bonding is btwn metal and metal
2. metal creates giant metallic lattice structure -> lattice of positive ions in a sea of mobile electrons
3. metallic bond btwn positively charged metals and sea of negatively charged mobile electrons

Question 7

What are the physical properties of metallic bonds ?

Answer 7

1. high mp bp
2. good conductor of electricity
   sea of delocalised electrons
3. malleable and ductile
   pure metal contains atoms of same size and arranged in regular, orderly manner -> layers of atoms can slide across each other easily when force is applied
   sea of mobile electrons continue to hold metal together
4. good thermal conductivity
   rapid collision of mobile electrons
5. insoluble in organic solvents, some metals rxt with water to form metal hydroxide + hydrogen gas

Question 8

What are alloys ?

Answer 8

1. mixture of a metal with one or more other elements
2. stronger and harder than pure metal
3. layers cannot slide because atom size of other element added not the same as metal