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AS CHEM UNIT1 > 1.6 Periodicity > Flashcards

1.6 Periodicity Flashcards

1
Q

Explain the trend in IE down a group

A
  • decreases
  • more electrons so more shells so more electron shielding which outweighs the increase in nuclear charge, resulting in decreased nuclear attraction meaning less energy is required to remove an outer electron
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2
Q

Explain the trend in IE across a period

A
  • increases
  • electrons in same shell so no change in electron shielding but there is a greater nuclear charge as proton number increases so it is harder to lose the outer electron due to greater nuclear attraction
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3
Q

Explain the trend in the melting and boiling points of group 1

A
  • decreases as descend
  • metallic bonding held by attraction of nuclei to delocalised electrons
  • increase in size due to increased protons means greater distance between therefore weaker attraction so can be more easily pulled apart to liquid/gas
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4
Q

Explain the trend in B+M point in group 7

A
  • increases as you descend
  • number of electrons increases resulting in larger induced dipoles and therefore stronger van der waals forces so more energy is required to break
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5
Q

Explain the trend of M+B point across a period

A
  • level attraction between positive nuclei and delocalised electrons increases
  • G1-G3 has increased charge due to more delocalised electrons therefore more attraction therefore stronger metallic bonds - more energy to break
  • G4 are giant covalent so strong covalent bonds
  • G5 sees change from covalent to simple molecular so van der waals need breaking hence decreased energy
  • G5-G8 the larger molecules have stronger van der waals due to more electrons
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6
Q

Trends in electronegativity down a group and across a period

A
  • down: decrease due to shielding
  • across: increase due to increased nuclear charge
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7
Q

Reaction of lithium with oxygen and water

A
  • oxygen: shiny to dull, slow
  • water: effervesce, float around till dissolve
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8
Q

Reaction of sodium with oxygen and water

A
  • oxygen: fast change from shiny to dull
  • water: more effervesce, melt to form spherical shape, faster float
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9
Q

Reactions of potassium with oxygen and water

A
  • oxygen: instant change from shiny to dull
  • effervesce, burn w lilac flame, move v quick
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10
Q

Lithium flame

A

Red

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11
Q

Sodium flame

A

Orange yellow

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12
Q

Potassium flame

A

Lilac

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13
Q

Magnesium flame

A

White/colourless

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14
Q

Calcium flame

A

Brick red

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15
Q

Barium flame

A

Apple green

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16
Q

Strontium flame

A

Crimson

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17
Q

Copper flame

A

Green blue

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18
Q

Trends of group 2

A
  • all G2 nitrates are soluble
  • all G2 carbonates are insoluble
  • G2 hydroxides increase in solubility as descend
  • G2 sulfates decrease in solubility as descend
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19
Q

Colour of barium sulfate ppt

A

White

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20
Q

Group 2 carbonates

A
  • decompose on heating but produce metal oxide and carbon dioxide gas
  • require increased heat to decompose as descend as thermal stability increases
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21
Q

A species is oxidised if …

A

oxidation number increases

22
Q

A species is reduced if …

A

it’s oxidation number decreases

23
Q

What is a reducing agent?

A
  • metal or negative ion
  • donates electrons to another element
  • is oxidised itself
24
Q

What is an oxidising agent?

A
  • non-metal or positive ion
  • cause oxidation reactions
  • is reduced itself
25
Q

Solubility of G1 compounds

A
  • all soluble
26
Q

Reaction of G1 metals with acid

A
  • metal salt and water
  • react more strongly than G2
27
Q

Solubility of G2 nitrates and carbonates

A
  • nitrates are soluble
  • carbonates are insoluble
28
Q

G2 sulfates trend

A
  • less soluble as you descend
29
Q

G2 hydroxides trend

A
  • more soluble as you descend
  • due to lower attraction between OH- ions and 2+ as atom increases in size and so can be split easier
30
Q

G2 thermal stability trend

A
  • increases as you descend so more heat energy required as you descend
31
Q

How do you identify halides? Give relevant colours

A
  • add silver nitrate
  • chloride = white
  • bromide = cream
  • iodide = yellow brown
32
Q

How do you identify magnesium compounds?

A
  • add sulphuric acid
  • if magnesium present it gives solution, if not then a solid forms
33
Q

How do you identify barium compounds?

A
  • add sodium hydroxide
  • if barium present a solution forms, if not a solid forms
34
Q

Reaction of Mg with HCL

A
  • effervesce
  • Mg dissolve into solution
35
Q

Describe trend in reactivity of G2 metals with water

A
  • reactivity increase as descend
  • more shells so more shielding so decreased nuclear attraction (outweighs nuclear charge)
  • IE decreases
36
Q

How to prepare solution of sodium and carbonate

A
  • weigh appropriate mass of solid
  • dissolve mass in small volume of deionised water
  • add solution to 250cm3 volumetric flask using funnel
  • shake to mix
37
Q

Why might strongly heating carbonates be an issue when measuring their end mass?

A
  • some may begin to decompose
  • lead to lower mass recorded
38
Q

How could you test for the presence of carbonate?

A
  • add an acid
  • observe effervescence if carbonate present
39
Q

How could you test for sulfate ions?

A

Add barium chloride and look for a ppt

40
Q

Define volatility

A
  • how easily something can be vaporised
  • higher BP = harder to vaporise so lower volatility
41
Q

Explain reactivity trend in G7

A
  • decreases
  • increased nuclear charge blocked by increased electron shielding as distance between nucleus and outer shell increases, causing attraction to decrease which makes it harder to add an electron
42
Q

… reactive halogen displaces a … reactive halogen

A
  • more
  • less
43
Q

Define oxidising power

A

The power an element has to gain an electron

44
Q

Explain G7 in terms of oxidising agents

A
  • chlorine has ability to take electrons from both bromide and iodide ions. Bromine and iodine cannot reclaim these electrons which indicates that chlorine is a more powerful oxidising agent than Br and I
  • bromine more powerful oxidising agent than iodine as it can remove electrons from iodine that iodine cannot reclaim
45
Q

Explain G7 in terms of reducing agents

A
  • halide ions are good reducing agents as they donate electrons and are themselves oxidised
  • reducing power increases down group as electrons are easier to lose from larger ions due to decreased nuclear attraction
46
Q

Explain the origin of the colours in flame tests

A

Excited electrons move down energy levels

47
Q

Explain the term oxidising agent in terms of electron transfer

A

Metal or negative ion that removes electrons

48
Q

Explain the decrease in atomic radii across periods

A
  • increase protons
  • electrons added to same shell
  • shielding remain same so greater attraction to nucleus
49
Q

What is gravimetric analysis

A

A quantitive method for accurately determining the amount of a substance by selective precipitation of the substance from an aqueous solution

50
Q

A solution contains sodium chloride and sodium iodide. Added silver nitrate and then ammonia. Explain what occurred during this test

A
  • yellow ppt for iodide and white for chloride
  • on adding ammonia and shaking, white ppt dissolves which leaves yellow iodide ppt.
51
Q

How to obtain magnesium carbonate from a known mass of magnesium

A
  • add acid in excess to ensure all Mg react, forming a salt
  • add soluble carbonate in excess so that all Mg2+ ions precipitate
  • filter and dry
52
Q

State results of ammonia test for halide ions

A

AgCl: ppt dissolve to give colourless solution
AgBr: unchanged if dilute but dissolve if concentrated
AgI: ppt insoluble

AS CHEM UNIT1 (9 decks)

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