Periodic table(tests)

Question 1

define allotrope

Answer 1

different forms of the same element in the same state

Question 2

describe features of diamond

Answer 2

-very high melting point, due to 4 strong c-c bonds -extremely hard, c-c bonds act in c-c -non-conductive, all electrons held in tight covalent bonds -good thermal conductor -insoluble, with any solvent

Question 3

describe features of graphite

Answer 3

-arranged in sheets of flat hexagons -sheets are bonded together by london forces -sheets can slide over each other -delocalised electrons can move so is electrical conductor -strong covalent bonds on hexagonal sheets means graphite has a very high melting point insoluble in any solvent

Question 4

describe features of graphene

Answer 4

-one 2D layer of graphite -delocalised electrons(same as graphite) allow electrical conduction. without layers electrons can move faster=best electrical conductor known -delocalised electrons also strengthen covalent bonds making graphene extremely strong -single layer of graphene is transparent and extremely light

Question 5

define metallic bond

Answer 5

the strong electrostatic attraction between the positive ions and the negatively charged delocalised electrons

Question 6

why are metals good thermal conductors

Answer 6

metallic bonding means the delocalised electrons can pass kinetic energy to each other

Question 7

why are metals good electrical conductors

Answer 7

metallic bonding means the delocalised electrons can carry current

Question 8

why do metals have high melting and boiling points what are the 3 things that affect them

Answer 8

1) metallic bonds are strong. the more delocalised electrons the stronger the bonds. Mg²⁺>Na.
2) size of the metal ion, smaller ionic radius will hold electrons closer to the nuclei
3) lattice structure also affect the melting and boiling points

Question 9

why do metals have the ability to be shaped

Answer 9

no bonds holding specific ions together so metal ions can slide over eachother when structure is pulled.

this makes metals malleable and ductile

Question 10

explain the solubility of metals

Answer 10

• insoluble, except in liquid metals
• due to strength of metallic bonds

Question 11

define periodicity

Answer 11

trends in physical and chemical properties of elements as you go across the periodic table

Question 12

elements in a period have the

Answer 12

same number of shells

Question 13

elements in a group have the

Answer 13

same number of outer electrons

Question 14

what are the elements that touch the step ladder line

Answer 14

metalloids

Question 15

define ionisation

Answer 15

removal of one or more electrons from an atom or molecule, resulting in an ion forming

Question 16

define second ionisation energy

Answer 16

energy needed to change 1 mole of gaseous 1+ ions into 1 mole of gaseous 2+ ions

Question 17

define first ionisation energy

Answer 17

energy needed to remove 1 mole of electrons from 1 mole of gaseous atoms

Question 18

write the general equation for second ionisation energy

Answer 18

X⁺_(g) -> X²⁺_(g) + e^-

Question 19

write the general equation for first ionisation energy

Answer 19

X_(g) -> X⁺_(g) + e^-

Question 21

what 3 factors affect ionisation energy

Answer 21

1) atomic radius (affected by 2+3)
2) nuclear charge
3) shielding

Question 22

whats the trend in first ionisation energy across a period

Answer 22

increase

Question 23

whats the trend in first ionisation energy down an group

Answer 23

decrease

Question 24

what affects melting/boiling points when going across a period

Answer 24

type of bond

1) metal-meta bonds = high, increase across
2) giant covalent structures(B,C and Si) = highest, increases
3) simple molecular structures= london forces weak

Question 25

group 2 metals react with water to give

write equation

Answer 25

a metal hydroxide and hydrogen

M_(s) + 2H₂O_(l) -> M(OH)_2(aq) + H_2(g)

Question 26

group 2 elements react more readily

Answer 26

down the group because ionisation energies decrease

Question 27

when group 2 metals burn in oxygen you get

write general equation

Answer 27

solid white oxides

2M_(s) + O_2(g) -> 2MO_(s)

Question 28

when group 2 metals react react with dilute HCl you get

write general equation

Answer 28

a metal chloride and hydrogen

M_(s) + 2HCl_(aq) -> MCl_2(aq) + H_2(g)

Question 29

group 2 acids are know as

commonly used for

Answer 29

alkaline earth metals

neutralising acids

Question 30

boiling/melting points of halogens do what down the group and why

what happens to volatility

Answer 30

increase

strength of london forces increase as number of electrons increase

decreases down group

Question 31

what reactions do halogens do

write general equation

Answer 31

reduction to halide ions

X + e^- -> X^-

Question 32

are halogen oxidsing/reducing agents

Answer 32

oxidising

Question 33

whats the trend in reacitivity of halogens down the group

Answer 33

decreases

Question 34

define displacement reaction

Answer 34

a reaction where a more reactive element pushes out a less reactive element from an ionic solution

Question 35

when testing for halogens organic solvent can be added to form a solvent layer which has very different colours. what are the colours for iodine, bromine, chloring

Answer 35

iodine = violet/pink

bromine = orange/red

chlorine = very pale yelow/green

Question 36

• when testing for halides what test can be used
• hwo should this test be performed
• what are the results

Answer 36

silver nitrate test

1) dissolve in distilled water if solid
2) add each unknown substance to a test tube with dilte HNO₃
3) add AgNO₃ (silver nitrate)
observations: Cl^-=white prcpt

Br^-= cream prcpt

I^-=yelow prcpt

Question 37

if halides cant be identified via silver nitrate test what test can be used to further distinguish between halide precipitates

Answer 37

• add dilute ammonia, see if prcpt dissloves
• add conc ammonia, see if prcpt dissolves
  observ. : Cl^- : dissolves in dilue NH₃

Br^-= dissolves in conc. but not dilute NH₃

I^-= insouble

Question 38

define disproportionation

Answer 38

when an element is both oxidised and reduced in a single chemical reaction

Question 39

halogens undergo disproportionation reactions when they react with cold dilute alkali solutions

write the full and ionic equation for a halogen reacting with NaOH

Answer 39

full: X₂ + 2NaOH -> NaXO + NaX + H₂O
ionic: X₂ + 2OH^- -> XO^- + X^- + H₂O

Question 40

when testing for ions what order should the 3 tests be in

Answer 40

carbonates -> sulfates -> halides

Question 41

describe how you would carry out the 3 tests for carbonates -> sulfates -> halides

Answer 41

carbonates: 1)dilute strong acid -> CO₂ + H₂O
2) CO₂ released

Sulphates: 1)add barium nitrate Ba(NO₃)_2(aq)

2)white precipitate forms

Halides: 1)add nitric acid, then silver nitrate solution

2)precipitate forms colours = AgCl-white, AgBr-cream, AgI-yellow

Question 42

how do you test for ammonium ions

Answer 42

Ammonia gas: 1)add NaOH and warm

1) hold damp red litmus paper over test tube
2) turns blue

(also smells)