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AS Chemistry > Elements of Life: Group 2 ( Structure types & Bonding - S Block ) > Flashcards

Elements of Life: Group 2 ( Structure types & Bonding - S Block ) Flashcards

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1
Q

What block are group 2 elements

A

S block

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2
Q

Why are group 2 elements in the s block

A

Outer electrons are in an s subshell

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3
Q

What happens to atomic radius as you go down Group 2

A

Increases

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4
Q

Why does atomic radius increase as you go down the group

A
  1. More electrons
  2. More electron shells

( no. filled electron shells increases )

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5
Q

What happens to 1st ionisation as you go down group 2

A

Decreases

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6
Q

Why does 1st ionisation decrease as you go down group 2

A
  1. More shells
  2. Distance between nucleus + outer shell increases
  3. More shielding ( from larger no. of inner electrons

= attraction between nucleus and outer electrons decreases

(atomic radius increases
no. filled electron shells shielding outer shell increases)

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7
Q

What happens to reactivity as you go down group 2

A

Increases

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8
Q

Why does reactivity increase as you go down group 2

A
  1. More shells
  2. Distance between nucleus + outer shell increases
  3. More shielding ( from larger no. of inner electrons

= attraction between nucleus and outer electrons decreases

(atomic radius increases
no. filled electron shells shielding outer shell increases)

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9
Q

What happens in group 2 reactions

A

Group 2 atoms lose outer their 2 outer electrons to form 2+ ions

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10
Q

What is required for group 2 atoms to lose their 2 outer electrons to form 2+ ions

A

Absorption of an amount of energy equal to the sun of the 1st and 2nd ionisation energies

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11
Q

Show the rule for ionisation energies of group 2 atoms in terms of equations

A

Mg (g) —> Mg 2+ (g) + 2e-

Requires:

1st + 2nd IEs

=738+1451
= 2189 kJmol -1

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12
Q

What are typical melting points of group 2 atom generally like

A

High

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13
Q

Why do group 2 atoms have high melting points

A
  1. Giant metallic structure

2. Strong electrostatic attraction between the lattice of positive ions and the sea of delocalised electrons

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14
Q

What happens to group 2 melting points as you go down the group

A

Decrease

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15
Q

Why does group 2 melting point decrease as you go down the group

A
  1. Atoms get bigger
  2. Distance between sea of electrons and positive nuclei increases
  3. Electrostatic attraction between positive ions and sea of delocalised electrons get weaker
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16
Q

What atom is the exception in group 2 melting point trend and why

A

Magnesium = lowest melting point = different lattice arrangement to other group 2 metals

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17
Q

What do group 2 metals burn in air to form

A

Oxides

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18
Q

Give equation of oxidation of group 2 metals using Mg as example

A

2Mg(s) + O2(g) —> 2Mg(2+)O(2-)

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19
Q

What are group 2 metal oxides also know as

A

Bases

20
Q

What do bases dissolved in water form to give ( and why )

A

Alkalis

O2- ion has a strong affinity (attraction) for H+ ions

21
Q

Give equation of group 2 oxides dissolved in water to give an alkali using Mg as example

A

Mg(2+)O(2-) (s) + H2O (l) —>

Mg(2+) (OH-)2 (s)

22
Q

What do group 2 metals reacting with water form

A

Hydrogen gas and alkaline solutions

23
Q

Give equation for group 2 metal reacting with water

X = any group 2 metal

A

X(s) + 2 H2O (l) —>

X(OH)2 (s) +H2 (g)

24
Q

What is special about the reaction of Mg with water

A

It is slow

Reacts fast with steam = magnesium oxide and hydrogen gas produced

25
Q

What do group 2 metal hydroxides dissolved in water form

A

Alkaline solutions

26
Q

Give the equation of group 2 metal hydroxides dissolved in water

X = any group 2 metal

A

X2+(OH-)2 (s) —>

X2+ (aq) + 2 OH- (aq)

27
Q

What happens to group 2 hydroxides solubility as you go down the group

A

Increase

28
Q

Why does solubility of group 2 hydroxides increase as you go down the group

X = any group 2 metal

A

As size of X 2+ ion increases attraction for OH- ions decreases

29
Q

What’s is the rule about about solubility and precipitate

A

Least soluble = precipitate

Most soluble = no precipitate

30
Q

What happens to strength of alkaline solution of group 2 metals as you go down the group

A

Increases

31
Q

How would you describe strongest alkali (I.e Barium)

A

Gives the highest concentration of OH- ions

32
Q

What happens to the solubility of group 2 sulphates as you go down the group

( similar trends for carbonates & chromates )

A

Decreases

33
Q

Describe magnesium sulphate (MgSO4)

A

Soluble = clear solution

34
Q

Describe barium sulphate ( BaSO4 )

A

Insoluble = white precipitate

35
Q

What is the insolubility of barium sulphate used to test for

A

Sulphate ions ( SO4 2- (aq) ) in an aqueous solution

Sulphate ions present = white precipitate of BaSO4 (s)

36
Q

Definition of thermal decomposition

A

Substance breaks down into simpler substances when heated

37
Q

What decomposes on heating

A

Metal carbonates = metal oxide + carbon dioxide

38
Q

Give equation of thermal decomposition of group 2 metal carbonates

X= any group 2 metal

A

heat

XCO3 (s) ——> XO (s) + CO2 (g)

39
Q

What happens to thermal stability of group 2 carbonates as you go down the group

A

Increases

40
Q

Why does thermal stability of group 2 carbonates increases as you go down the group

A
  1. Size of ions increases
  2. Polarising power decreases
  3. Higher temp needed to decompose carbonate ion
41
Q

High charge density =???

A

High polarising power

42
Q

High polarising power =???

A

High charge density

43
Q

What happens to polarising power ( charge density ) as you go down the group and why

A

Decreases because metal ions increase in size

44
Q

Why do metal ions with a high charge density ( high polarising power ) decompose easier on heating

A

They distort the electron cloud of the carbonate ion

45
Q

Can group 1 carbonates decompose on heating

A

No because have low polarising power

46
Q

What is the name of group 2 metals

A

Alkaline earth metals

AS Chemistry (43 decks)

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