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y4 chem > patterns in periodic table > Flashcards

patterns in periodic table Flashcards

(43 cards)

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1
Q

what is the periodic table

A

arrangement of the elements in order of increasing proton / atomic number

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2
Q

elements in the same group..

A
  • have the same number of valence electrons
  • increase in metallic properties down the group
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3
Q

elements in the same period…

A
  • have the same number of electron shells / principal quantum shells
  • decrease in metallic properties across the period
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4
Q

what is atomic radius

A

half the distance between two nuclei of a diatomic molecule

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5
Q

factors affecting atomic radius

A

nuclear charge
shielding effect

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6
Q

what is nuclear charge

A

attractive forces of positively charged nuclear protons acting on valence electrons , depends on the number of protons

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7
Q

what is shielding effect

A

repulsion between electron shells, prevents valence electrons from experiencing full nuclear charge due to repulsion of inner electrons

depends on number of electron shells

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8
Q

how does atomic radius change down a group

A

increases down a group
- no. of principal quantum shells increases → distance between nucleus and valence electrons increases → shielding effect experienced by valence electrons increases
- despite increasing nuclear charge, EFOA between nucleus and valence electrons decreases, so size of electron cloud increases

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9
Q

how does atomic radius change across a period

A

decreases across a period
- even though number of electrons increases, electrons are added to the same outermost shell so shielding effect is approximately constant
- number of protons increases, so nuclear charge increases
- effective nuclear charge increases, EFOA between nucleus and valence electrons increases, resulting in decrease in size of electron cloud

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10
Q

what are group 1 elements

A

alkali metals

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11
Q

properties of group 1 elements

A
  • soft and can be easily cut
  • low melting and boiling points (decrease down the group)
  • low densities (increase down the group)
  • highly reactive (increases down group)
  • react with water to form alkalis and hydrogen gas
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12
Q

why do melting and boiling points of group 1 metals decrease down the group

A

atomic radius increases → distance between nucleus and delocalised electrons increases → weaker EFOA → easier to overcome EFOA

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13
Q

what are group 17 elements

A

halogens

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14
Q

properties of group 17 elements

A
  • exist as diatomic molecules
  • low melting and boiling points (increase down group)
  • coloured (colour intensity increases down group)
  • reactivity decreases down group (atomic radius increases, making it more difficult to attract electrons)
  • react with most metals to form halide salts
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15
Q

colours of group 17 elements

A

fluorine: pale yellow (gas at rtp)
chlorine: yellow-green (gas at rtp)
bromine: red-brown (liquid at rtp)
iodine: purple-black (solid at rtp)
astatine: black (solid at rtp)

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16
Q

why do the melting and boiling points of group 17 elements increase down the group

A
  • atomic radius increases → stronger IMF between molecules → harder to overcome IMF
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17
Q

group 17 elements displacement reactions

A
  • more reactive halogen displaces a less reactive halogen from its halide solution
  • fluorine does not undergo displacement reactions as it is too reactive
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18
Q

chlorine displacing bromine

Study These Flashcards
A

cl2(aq) + 2br- (aq) → 2cl- (aq) + br2 (aq)
colourless KBr solution turns orange

19
Q

chlorine displacing iodine

Study These Flashcards
A

cl2 (aq) + 2I- (aq) → 2cl- (aq) + I2 (aq)
colourless KI solution turns brown

20
Q

bromine displacing iodine

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A

br2 (aq) + 2I- (aq) → 2br- (aq) + I2 (aq)
colourless KI solution turns brown

21
Q

what are group 18 elements

22
Q

properties of group 18 elements

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A
  • colourless at rt
  • low melting and boiling points
  • insoluble in water
  • used to provide an inert atmosphere (helium in balloons, argon in welding)
  • monatomic
  • chemically unreactive (inert) (fully filled valence shell)
23
Q

what are group 3-11 elements

Study These Flashcards
A

transition metals

24
Q

properties of transition metals

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A
  • high melting and boiling points
  • high density
  • coloured
  • variable oxidation states in their compounds
  • good catalysts (iron in haber process, nickel to manufacture margarine)
25
similarities between alkali metals and transition metals
- conduct electricity - conduct heat - shiny in appearance - malleable and ductile
26
differences between alkali metals and transition metals
hardness: very soft vs hard m.p. and b.p. : low vs high density: low vs high oxidation states: +1 vs variable colour of compounds: white solids, colourless solutions vs coloured catalytic property: none vs yes
27
reactivity series in order
potassium, sodium, calcium, magnesium, aluminium, carbon, zinc, hydrogen gas, iron, tin, lead, hydrogen ions, copper, silver, gold, platinum
28
why does aluminium appear to be chemically inert
it readily reacts with oxygen in air to form an insoluble aluminium oxide layer around the metal, preventing it from further reaction
29
reaction of metals with cold water
- more reactive metals react violently with cold water - metal + water → metal hydroxide + hydrogen - only potassium, sodium, calcium, and magnesium react with cold water, except iron which reacts very slowly in the presence of air (rusting) - reactions decrease in violence down reactivity series
30
reaction of metals with steam
- more reactive metals react more violently with steam - metal + steam → metal oxide + hydrogen - metals from potassium to iron react with steam - hot mg reacts violently, bright white glow produced - hot zinc reacts readily, zinc oxide yellow when hot white when cold - hot fe reacts slowly, must be constantly heated for reaction to progress
31
reaction of metals with dilute hcl
- metal + hcl → metal chloride + hydrogen - metals above hydrogen (ions) in the reactivity series react with hcl - but lead does not react as lead(ii) chloride forms an insoluble layer around the lead, preventing further reaction
32
reduction of metal oxides with carbon
- only metal oxides below carbon can be reduced by it. metal oxides closer to carbon in reactivity series require higher temperatures for reduction - metal oxide + carbon → metal + carbon dioxide
33
reduction of metal oxides with hydrogen
- only metal oxides below hydrogen (gas) can be reduced by it - metal oxides closest to hydrogen in the reactivity series require highest temperatures for reduction - metal oxide + hydrogen → metal + steam
34
metal displacement reactions
- more reactive metal displaces less reactive metal from its salt solution - redox reactions
35
colours of solutions
copper(ii) nitrate → blue iron(ii) nitrate → pale green magnesium, zinc, lead → colourless
36
colours of metals
zinc, lead, iron → grey copper → red brown
37
action of heat on metal carbonates
- the more reactive the metal, the more difficult it is to decompose its carbonate by heat - K and Na carbonates are very stable to heat and unaffected by heat - Ca to copper decompose into metal oxides and co2 upon heating - silver decomposes into silver and co2 as silver oxide is thermally unstable and further decomposes to form silver
38
colours of carbonates before and after heating
potassium: white and white sodium: white and white zinc: yellow when hot, white when cool lead: white, yellow copper (ii): green, black
39
what are hydrated salts
- ionic compounds that contain water within their crystal structure - upon heating, water is expelled as water vapour, leaving anhydrous salt behind
40
41
how to extract metals that are more reactive than carbon (difficult to break down)
electrolysis
42
conditions for rusting
- only iron undergoes rusting (steel too, since it contains iron) - water and oxygen - sodium chloride increases rate of rusting (provides mobile ions in solution, making it a strong electrolyte that facilitates rusting)
43
rust prevention methods
- barrier: painting, oiling/greasing, coating with plastic - sacrificial protection: use of a more reactive metal that oxidises preferentially to corrode in place of iron and steel

y4 chem (2 decks)

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