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AS CHEMISTRY (UNIT 2) > 2.11 Group II Metals and their compounds > Flashcards

2.11 Group II Metals and their compounds Flashcards

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1
Q

S-block element

A

An element which has an atom with highest energy/outer electron in an s-subshell (orbital).

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2
Q

Where are Group II elements found

A

• Group II metals are isolated from ores (mostly carbonates) found in the Earth’s crust.

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3
Q

What is the other term for Group II metals

A

Alkaline Earth Metals

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4
Q

Why do they have similar chemical properties

A

Each have full s-subshell (2 electrons in outer shell)

Reactivity increases down the group

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5
Q

Why does Atomic/ionic radius increases down the group

A

o Complete electron shell is added as the group descends

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6
Q

Why is Ionic radius smaller than atomic radius

A

Greater proton:electron ratio

Greater electrostatic attraction between positive nucleus and the negatively charged outer electrons causing outer electrons to be pulled closer to the nucleus.

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7
Q

Why does First Ionisation energy decrease down the group i.e why do they become more reactive down the group?

A

Complete electron shell added as the group descends
This causes an increase in atomic radius
This causes an increase in the shielding effect

Both cause the electrostatic attraction between the positively charged nucleus and the negatively charged outer electrons to decrease therefore less energy is required to remove an electron

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8
Q

Why is second ionisation energy significantly lower than first

A

Proves that Alkaline Earth Metals readily lose 2 electrons (from outer shell)to form M2+

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9
Q

Method for the Combustion of Group II Metals

A
  1. Measure the mass of a crucible and lid using a balance
  2. Add some metal and measure the mass of the crucible, lid and metal
  3. Place the crucible on a pipeclay triangle and heat strongly (for 5mins), raising the lid at intervals to allow air into the crucible
  4. Allow the crucible to cool and weigh
  5. Repeat the heating, cooling and weighing until there is “constant mass”
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10
Q

Equation for the combustion of metal in oxygen

A

Group II metal + Oxygen => Metal Oxide
2M + O2 =>2MO

Heating heavy metal (e.g. Barium) in O2 rich environment can produce a Metal peroxide (MO2)

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11
Q

Observations for Group II metals burned in Oxygen

A

Mg - Burns with a bright white light to produce white solid
Ca - Burns with a red flame to produce white solid
Sr - Burns with a crimson flame to produce white solid
Ba- Burns with an apple green flame to produce white solid

Always exothermic
Always white solid

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12
Q

Group II metal and Water

A 
Metal Hydroxide (M(OH)2) formed
oWhite solid

Produces an alkaline solution (because of the hydroxide produced

Reaction increases with vigour as group descends

N.B- Mg(OH)2 insoluble
N.B- Ca(OH)2 slightly soluble

•Solubility of Hydroxides increases down the group

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13
Q

Equation for reaction of Group II with water

A

Group II Metal + Water => Metal Hydroxide + Hydrogen gas

M + 2H2O =>M(OH)2 + H2

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14
Q

Observations with Mg and Water

A
  • Few bubbles produced slowly

* Metal dulls

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15
Q

Observations with Calcium and Water

A 
•	Fizzing (gas released)
•	mixture warms up 
•	metal rises and falls (Heat from the 
        reaction warms the water causing it to 
        rise)
•	metal disappears
•	white solid produced
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16
Q

Observations with Mg and Steam

A
  • Burns with a bright white light
  • Heat released
  • White solid produced
17
Q

Reaction of Group II metal and acid

A

• Reaction increases with vigour as group descends
• Metal atoms are reducing agents
• H+ ion is reduced
• If reacted with a strong acid, resulting aqueous solution formed has pH
approx. 7

18
Q

Equation for reaction of Group II metal and acid

A

Group II Metal + Acid => Metal salt + Hydrogen

19
Q

Observations with Group II metal and HCL

A
  • metal disappears
  • fizzing
  • mixture warms up
20
Q

Observations with H2SO4 and Magnesium

A
  • metal disappears
  • fizzing
  • mixture warms up
21
Q

Observation with H2SO4 and Calcium

A

• fizzing initially but reaction stops

Due to formation of insoluble calcium sulfate
forms an unreactive layer over the surface of the Calcium (prevents H+ ions reaching metal surface)

22
Q

Properties of Group II compounds

A

• When Group II metal atom (M) reacts, it loses electrons to form the M2+ ion
Therefore, product formed is an ionic compound as a crystalline solid
• M2+ ions in a Group II compound do not absorb visible light
Therefore, product formed is a white crystalline solid

23
Q

Group II oxides and water

A

Metal oxide + Water => Metal Hydroxide
MO + H2O => M(OH)2

N.B- Mg(OH)2 insoluble
N.B- Ca(OH)2 slightly soluble
•Solubility of Hydroxides increases down the group

24
Q

Reaction of limewater and CO2

A

CaO + H2O => Ca(OH)2 (Limewater)

Ca(OH)2 + CO2 => CaCO3 + H2O

CaCO3 + H2O + CO2 => Ca(HCO3)2

25
Q

Observations of limewater and CO2

A

Observations

•Limewater goes from colourless to milky white ppt.

26
Q

Reaction of Group II oxides and acid

A

•Oxides are bases
Therefore, neutralised by acid

Metal oxide + Acid => Metal salt + Water

27
Q

What is the benefit of CaCO3 in toothpaste

A

oNeutralises acid deposited on surface of teeth by bacteria which can cause dental decay if left untreated
oCaCO3 is insoluble and acts as a mild abrasive for cleaning

28
Q

Equation for metal and steam

A

Metal + Steam => Metal oxide + Hydrogen

29
Q

why are bases such as CaCO3 and Mg(OH)2 used in antacids

A

Neutralises excess stomach acid

30
Q

Equation for metal carbonate and acid

A

Metal carbonate/hydrogencarbonate + acid => Metal salt + water + carbon dioxide

When all acid has been reacted, no effervescence is observed
(Can be used to identify if acid is in excess; if so, there would be effervescence)

31
Q

Equation for thermal decomposition of Metal Carbonates and hydroxides

A

Carbonate => Metal oxide + Carbon dioxide gas
MCO3 => MO + CO2

Hydroxide => Metal oxide + steam
M(OH)2 => MO + H2O

AS CHEMISTRY (UNIT 2) (3 decks)

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