S3.1 The periodic table: classification of elements Flashcards

1
Q

what does the periodic table consist of

A

periods, groups, blocks

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2
Q

how are elements arranged

A
  • arranged in increasing atomic number
  • atoms with the same number of shells are together
  • atoms with similar outer shell electron configurations are together
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3
Q

helium and hydrogen are unusual

A

so are put into a group based on similarities in physical and chemical properties
He = 0
H = group of its own

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4
Q

s block

A

only s electron in outer shell

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5
Q

p block

A

minimum 1 p electron in outer shell

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6
Q

d block

A

minimum 1 d electron and 1 s electron in outer shell, no p or f electron in outer shell

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7
Q

f block

A

minimum 1 f electron and 1 s electron in outer shell, no d or p electron in outer shell

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8
Q

atomic radius trend down a group

A
  • General increase
  • More shells
  • Electrons in inner shells repel electrons in outer shells
  • Shielding from positive nuclear charge
  • Less attraction between outer shell electron and nucleus → larger atoms
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9
Q

atomic radius trend across a period

A
  • General decrease
  • Increased atomic number, increased nuclear charge, more electrons added to same principal quantum number shell
  • Larger nuclear charge, greater nuclear attraction between outer shell electron and nucleus → smaller atoms
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10
Q

when does the ionic radius increase

A

with increasing negative charge (more repulsion, more electrons while constant nuclear charge)

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11
Q

when does the ionic radius decrease

A

with increasing positive charge (greater electrostatic force of attraction, less electrons while constant nuclear charge)

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12
Q

electronegativity

A

ability of atom to attract a pair of electrons towards itself in a covalent bond

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13
Q

electronegativity trends across a period

A
  • Increase
  • Greater nuclear charge, same shielding
  • Nucleus has increasingly strong attraction to electrons → smaller atomic radii
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14
Q

electronegativity trends down a group

A
  • Decrease
  • Nuclear charge increases, increased shielding, larger atomic radii
  • Decrease in attraction between nucleus and outer electron, decreased effective nuclear charge
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15
Q

electron affinity trends

A

Don’t include noble gases as they don’t form negative ions
Most exothermic electron aff = group 17
Strongest pull on electron is correlated with greater energy released when -ve ions form

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16
Q

electron affinity trend down a group

A
  • general decrease
  • As atoms become larger, the attraction for an additional electron is less, the effective nuclear charge reduces due to shielding
  • Becomes less exothermic (fluorine is an exception)
  • fluorine has a very small electron affinity, it is such a small atom, additional electron in 2p subshell experiences repulsion with other valence electrons
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17
Q

group 1: alkali metals

A
  • Form high pH alkaline solutions when reacted with water
  • End in ns1 electron configurations
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18
Q

alkali metals physical properties

A
  • Soft, easy to cut, softer denser down group
  • Shiny silver surface when cut
  • Conduct heat and electricity
  • Low MP, low densities
  • MP decreases down group, increased atomic radius, weaker metallic bonding
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19
Q

alkali metals chemical properties

A
  • Readily react with oxygen and water vapour in air (kept in oil to stop)
  • Similar reactions with water- vigorous, produce alkaline metal hydroxide and hydrogen gas
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20
Q

lithium + water

A

2Li(s) + 2H2O(l) → 2LiOH(aq) + H2(g)
- Lithium floats, slowly reacts
- Hydrogen gas released
- Lithium keeps shape

21
Q

sodium + water

A

2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
- Vigorous hydrogen gas release
- Heat produced melts unreacted metal, forms small ball that moves on surface
- Highly alkaline solution due to NaOH

22
Q

potassium + water

A

2K(s) + 2H2O(l) → 2KOH(aq) + H2(g)
- Bubbles of hydrogen gas
- Melts into shiny ball, dashes around surface
- Hot enough to ignite hydrogen gas
- K burns with lilac flame

23
Q

alkali metals with halides

A
  • Vigorous reactions
  • Product is an alkali halide salt
    2Na (s) + Cl2 (g)–> 2NaCl (s)
  • Increasingly vigorous down group: larger atom, ns1 electron further from nucleus, is shielded, easier to lose electron
24
Q

what do metallic oxides form when reacting with water

A

hydroxides

25
Q

what do non metallic oxides form when reacting with water

A

oxoacids

26
Q

what does the acid-base character of oxides give evidence of

A

chemical trends

27
Q

how do oxides change across a period

A

basic → amphoteric → acid

28
Q

amphoteric

A

can act as acid and base

29
Q

oxides: trend across a period

A

Oxides become less ionic
Due to increased electronegativity

30
Q

oxides: trend down a group

A

Oxides become more ionic
Due to decreased electronegativity

31
Q

oxidation state

A
  • a number assigned to an atom to show the number of electrons transferred in forming the bond
  • it is the change the atom would have if the compound were composed of ions
32
Q

what will always have a negative value

A

the more electronegative species

33
Q

sum of oxidation numbers in a compound

A

= 0

34
Q

sum of oxidation numbers in an ion

A

= charge of the ion

35
Q

group 1 oxidation state

A

+1

36
Q

group 2 oxidation state

A

+2

37
Q

fluorine oxidation state

A

-1

38
Q

hydrogen oxidation state

A

+1

39
Q

hydrogen in metal hydrides oxidation state

A

-1

40
Q

oxygen oxidation state

A

-2

41
Q

oxygen in peroxides oxidation state

A

-1

42
Q

oxygen in F2O oxidation state

A

+2

43
Q

uncombined element oxidation state

A

0

44
Q

naming transition metal compounds

A
  • Stock notation (roman numerals) if variable oxidation number
    E.g. iron (+2, +3), iron (II) oxide
  • generic names persist and are acceptable
45
Q

generic names: nitrate

A

NO3-

46
Q

generic names: nitrite

A

NO2-

47
Q

generic names: sulfate

A

SO4 2-

48
Q

generic names: sulfite

A

SO3 2-