1.2 - elements and bonding

Question 1

what are the three trends in the periodic table?

Answer 1

• covalent radius
• ionisation energy
• electronegativity

Question 2

what is the covalent radius?

Answer 2

a measure of the size of the atom

Question 3

what happens to the covalent radius when going across a period and why?

Answer 3

• the covalent radius gets smaller
• due to the increasing number of protons in the nucleus which pulls electrons closer, making the atom smaller

Question 4

what happens to the covalent radius when going down a group and why?

Answer 4

• the covalent radius gets bigger
• due to the increasing number of energy levels

Question 5

what is ionisation energy?

Answer 5

the energy required to remove one mole of electrons from a mole of gaseous atoms (always an endothermic process)

Question 6

what happens to the ionisation energy when going across a period and why?

Answer 6

• ionisation energy increases
• due to the increasing number of protons, making it more difficult to remove outer electron

Question 7

what happens to the ionisation energy when going down a group and why?

Answer 7

• ionisation energy decreases
• due to the increasing number of energy lelevs
• due to the increases screening effect

Question 8

what is the senond ionisation energy?

Answer 8

the energy required to remove a further mole of electrons from a mole of gaseous ions

Question 9

why is the second ionisation energy value significantly larger than the first?

Answer 9

because the second electron is being removed from:
- an energy level closer to the infulence of the nucleus
- an energy level where there is less of a screenng effect
- a filled energy level which is stable

Question 10

what is electronegativity?

Answer 10

the power of an atom to attract bonding electrons to itself

Question 11

what happens to the electronegativity when going across a period and why?

Answer 11

• electronegativity increases
• due to the increasing number of protons
• due to bonding electrons being closer to the nucleus

Question 12

what happens to the electronegativity when going down a group and why?

Answer 12

• electronegativity decreases
• due to the increasing number of energy levels
• due to the increases screening effect: nucleus is less able to attract bonding electrons

Question 13

why are noble gases not given an electronegativity value?

Answer 13

because they already have a full shell of electrons and are stable so have no need for attracting electrons

Question 14

what is a metalic bond?

Answer 14

positively charged ions that attract a pool of delocalised electrons

Question 15

what are three properties of metals due to delocalised electrons?

Answer 15

• good eelctrical conductors
• bendable (malleable)
• can be shaped into wires (ductile)

Question 16

what happens to the melting point of metals as you go down a group?

Answer 16

the melting point decreases down the group because the size of the atoms increase causing the delocalised electrons to be further away from the positive nucleus, which weakens the metallic bonds

Question 17

what is a covalent network?

Answer 17

atoms held together by strong covalent bonds in a giant network structure

Question 18

what is the structure of diamond?

Answer 18

• each carbon bonds four times
• does not conduct as all the carbon electrons are used in bonding

Question 19

what is the structure of graphite?

Answer 19

• each carbon bonds three times
• conducts electricity as only three of the carbon outer electrons are used in bonding
• each carbon atom contributes one elctron to a pool of delocalised electrons

Question 20

what seven elements are metallic out of the first 20 in the periodic table?

Answer 20

• lithium
• beryllium
• sodium
• magnesium
• aluminium
• potassium
• calcium

Question 21

what seven elements are covalent molecular out of the first 20 in the periodic table?

Answer 21

• hydrogen
• nitrogen
• oxygen
• fluorine
• chlorine
• phosphorus (P4)
• sulfur (S8)

Question 22

what else is covalent molecular alongside the seven elements?

Answer 22

fullerenes e.g. C60

Question 23

what four elements are covalent networks?

Answer 23

• carbon in the form of graphite
• carbon in the form of diamond
• silicon
• boron

Question 24

what elements are monatomic?

Answer 24

noble gases

Question 25

what type of bonding do covalent network substances have present?

Answer 25

covalent bonding

Question 26

what are the melting points of colavent networks and why?

Answer 26

extremely high due to the strong covalent bonds throughout the structure which must be broken to melt the substance

Question 27

what two types of bonding do covalent molecular elements have present?

Answer 27

• covalent bonding
• L.D.Fs

Question 28

what happens to L.D.F attractions when molecyular substances are heated?

Answer 28

• when molecular substances are heated the L.D.F attractions are overcome
• the stronger these attractions are the higher the melting points and boiling points

Question 29

what form/state are diatomic molecular elements in at room temperature and why?

Answer 29

• gases
• because they have fewer eelctrons therefore weaker L.D.Fs therefore lower melting points

Question 30

what form/state are phosphorus and sulfur in at room temperature and why?

Answer 30

• covalent molecular solids at room temperature
• because the forces of attraction are stronger and therefore the melting points are higher

Question 31

what happens as the size of a molecule increases?

Answer 31

the number of electrons increases and the strength of the L.D.Fs increase, leading to higher melting and boiling points

Question 32

what happens to the boiling point of the noble gases going down the group?

Answer 32

• increases
• as the number of electrons in the atom increases, the strength of the london dispersion forces increases, increasing the boiling point