chemical bonding 3

Question 1

define metallic bonding

Answer 1

strong electrostatic attraction of a lattice of cations to a sea of delocalised electrons

Question 2

what are the physical properties of metals?

Answer 2

-high melting and boiling points
-good electrical conductors

Question 3

why are metals good electrical conductors?

Answer 3

delocalised electrons are mobile and can carry charge

Question 4

why do metals have high melting and boiling points?

Answer 4

strong electrostatic attraction between the lattice of cation and delocalised electrons
-so lots of energy needed to break the strong metallic bond

Question 5

whats a lattice?

Answer 5

regular repeating arrangements of particles in a pattern

Question 6

whats the ionic compound structure?

Answer 6

the solid structure of a giant ionic lattice results from the electrostatic attraction between oppositely charged ions

Question 7

what is needed for conductivity?

Answer 7

must contain mobile charge carriers:
-delocalised electrons
-mobile ions

Question 8

physical properties of ionic compounds

Answer 8

-high melting and boiling points
-cant conduct when solid
-good electrical conductors when molten or in aqueous solution
-soluble in water

Question 9

why do ionic compounds have high melting and boiling points?

Answer 9

-strong electrostatic attraction between oppositely charged ions
-so lots of energy needed to break the ionic bonds

Question 10

why are ionic compounds soluble in water?

Answer 10

-as polar water molecules are attracted to the positive and negative ions and the giant ionic lattice breaks down
the water molecules completely surround the ions

Question 11

give 2 examples of simple covalent structures

Answer 11

iodine
ice

Question 12

describe bonding in simple covalent compounds

Answer 12

-weak forces of attraction between the molecules
-the atoms within the molecules are bonded together by strong covalent bonds

Question 13

describe why ice is describes as having a simple covalent molecular lattice structure

Answer 13

-H2O has covalent OH bonds within the molecule
-hydrogen bonds between the H2O molecules are weak and need little heat energy to break so simple covalent structure
-regular arrangement of H2O molecules so has lattice structure

Question 14

explain 3 properties of simple covalent substances

Answer 14

-low melting and boiling points = less energy needed to overcome weak forces of attraction between molecules
-dont conduct electricity = no mobile charge carriers as all electrons are localised in covalent bonds
-soluble in non-polar solvent = can form london forces with non-polar solvent molecules

Question 15

what are giant covalent lattices?

Answer 15

solids which are networks of atoms bonded together by strong covalent bonds

Question 16

explain the properties of giant covalent molecules

Answer 16

-very high melting points = all strong covalent bonds between C atoms so lots of heat energy needed to break the covalent bonds
-does not conduct electricity = no mobile charge carriers as all electrons fixed in covalent bonds

Question 17

describe the structure of graphite

Answer 17

-trigonal planar- =120 degrees - 3 bonding pairs of electrons around central C atom
-only 3 of 5 outer electrons used in covalent bonding and form
-planar interlocking hexagonal layers which can slide over each other.
-london forces between layers
so one delocalised electron can move between layers
-

Question 18

describe the properties of graphite

Answer 18

-high melting point = many strong covalent bonds between C atoms so lots of energy needed to overcome the covalent bonds
-conducts electricity = delocalised electrons which can move between the layers and carry charge

Question 19

describe the structure of graphene

Answer 19

single layer of graphite
composed of hexagonally arranged carbon atoms linked by strong covalent bonds

Question 20

describe the properties of silicon

Answer 20

-very high melting and boiling points = all strong covalent bonds between atoms need alot of energy to break
-does not conduct electricity = electrons localised/ fixed in covalent bonds