1.3 Bonding

Question 1

What is ionic bonding

Answer 1

• a metal and non metal
• 3d lattice structure
• a high bp and mp because of strong electrostatic forces of attraction between oppositely charged ions
• soluble in water
• good electrical conductor when molten or dissolved because ions are free to move and carry charge
• strength of ionic bond depends on charge of ion eg+ or 2+

Question 2

What happens when you put a ionic substance in water

Answer 2

Ions separate. Water is a polar molecule
Eg. NaCl
An+ is attracted to O- and Cl- is attracted to H+

Question 3

What is covalent bonding?

Answer 3

• two metals share a pair of electrons
• IN SIMPLE MOLECULAR there is a low bp and mp because of weak intermolecular (CDW/DD/hydrogen)
• IN GINAT MOLECULAR there is a high bp and mp cos of lots of strong covalent bonds
• doesn’t conduct electricity cos no delocalised electrons or ions
• slightly soluble

Question 4

Give examples of covalent substances

Answer 4

Diamond, graphite, graphene and buckminster fullerene

Question 5

Structure and function of diamonds

Answer 5

• carbon joined to 4 other carbons in v strong tetrahedral shape + doesn’t conduct
• strong covalent bonds so high bp and mp

Question 6

Structure and function of graphite

Answer 6

• layers of hexagonal rings hells together by van der waals forces
• carbon bonded to 3 other carbons so can conduct
• layers can slide over each other so soft o
• high bp and mp cos there’s lots of strong covalent bonds

Question 7

Structure and function of graphene

Answer 7

• single layer of graphite
• strong
• carbon bonded to 3 others so can conduct

Question 8

Structure and function of buckminster fullerene

Answer 8

• carbons bonded to 3 others carbon so can conduct
• high SA:vol ratio

Question 9

What is metallic bonding?

Answer 9

• positive cations surrounded by delocalised electrons
• high mp and bp cos of strong electrostatic force of attractions between cations and electrons
• high bp if metal forms bigger charged ions eg. 2+ would lose two electrons therefore more delocalised electrons and stronger EFOA

Question 10

What is a pure metal?

Answer 10

Substance made of only one element, ions are all same size so layers can roll over each other
- high bp and mp cos strong EFOA
- good conductors of electricity and of thermal energy because of delocalised that are free to move through the structure and carry charge

Question 11

What happens to the melting point of metals as you move across the period and down the group

Answer 11

ACROSS - elements have to remove more electrons to have a full outer shell so higher EFOA
DOWN - top of groups have smaller radius and less shielding so stronger EFOA

Question 12

Define electronegativity

Answer 12

The ability of a atom to attract the two electrons in a covalent bond

Question 13

What factors affect electronegativity and how?

Answer 13

NUCLEAR CHARGE - if there is more protons, there is a stronger positive charge and therefore stronger attraction to negative electrons
ATOMIC RADIUS - if there is a smaller AR there electrons pair is closer to the nucleus therefore stronger attraction
SHIELDING - less shells of electrons between nucleolus and electrons means less repulsion to other electrons and stronger attraction to the nucleus

Question 14

What happens to electronegativity across a period?

Answer 14

• it increases
• increasing nuclear charge pulls outermost electrons towards nucleus, decreasing atomic radius. Greater attraction to the pair of electrons and therefore more likely to pull them towards itself

Question 15

What happens to electronegativity down a group?

Answer 15

-it decreases
- atomic radius increases therefore there is more shielding so less attraction between the nucleus and the electrons

Question 16

What is a nonpolar and a polar bond

Answer 16

NON POLAR - elements have the same electronegativity so no dipole dipole bond
POLAR - difference in electronegativity means pair of electrons shift slightly towards one of the nuclei. Chauses partial charge

Question 17

What are the intermolecular forces of attraction in order of weakest to strongest?

Answer 17

VAN DER WAALS - all molecules have these, causes by constant motion of electrons which leads to uneven distribution of negative charge at any moment
DIPOLE DIPOLE - attraction between two polar molecules, big enough different in ectronegativity (0.4-0.7)
HYDROGEN BONDS - forces between a hydrogen atom and nitrogen, oxygen or fluorine

Question 18

Describe the structure of iodine

Answer 18

Lattice structure w covalent bonds between the iodine atoms (cos I2) and weak VDW forces between iodide molecules

Question 19

Describe the structure of ice

Answer 19

When water freezes it forms hydrogen bonds between H2O molecules causing them to spread out. This means ice is less dense that water and float to the top of the liquid

Question 20

What does macromolecular mean?

Answer 20

A giant molecule with covalent bonding

Question 21

What is a dative bond?

Answer 21

A covalent bond where both of the electrons come from one atom. Only atoms with a lone pair can do this.