elements of life 8

Question 1

what happens as you go down the group ( metallic)

Answer 1

• elements become more metalic down a group they more readily from cation in ionic compounds
• the most reactive metals in group 1 and 2 are found at the bottoms each group

Question 2

what happenes across the period ( metallic)

Answer 2

• elements become less metallic across a period from left to right
• the group 1 metals are more reactive than the group 2 metals in the same period

Question 3

what happens to the reactivity as you go down the 1-2 group ?

Answer 3

• as you go down it is more reactive as the electrons are easily broken away from the outter shell
• so less energy needed

Question 4

Define “first ionisation enthalpy”.

Answer 4

The energy needed to remove one electron from each of one mole of isolated gaseous atoms of an element, forming one mole of gaseous 1+ ions.
* It removes the most lowley held electron
* this will be one of the outer shell electrons since they are furthest from the nuclues

Question 5

what is the generl equation for the first ionisation :

Answer 5

X(g) = X+(g) +e-

Question 6

Define “second ionisation enthalpy”.

Answer 6

The energy needed to remove one electron from each of one mole of isolated gaseous 1+ ions of an element, forming one mole of gaseous 2+ ions.

Question 8

State and explain the trend in ionisation enthalpies across periods.

Answer 8

Ionisation enthalpy increases across periods:

• All outer electrons in a period are in same shell
• Proton number increases so greater electrostatic attraction between outer electrons + nucleus
• So more energy required to remove an electron

Question 9

State and explain the trend in ionisation enthalpies down groups.

Answer 9

Ionisation energies decrease down groups:

• More electron shells
• Distance between nucleus + outer shell increases
• Weaker electrostatic attraction
• Easier to remove an electron

Question 10

where are group 1 shown on the ionisation graph

Answer 10

they are shown in troughs

Question 11

How does observed data of 1st ionisation enthalpies provide evidence for:

electron shells?
electron sub-shells?

Answer 11

Electron shells

• Ionisation enthalpy decreases down groups
• Supports idea that inner shells shield outer ones, causing less attraction to nucleus
  Electron sub-shells

-Ionisation enthalpy increases across periods, with variations
-So energy needed to remove electrons depends on their location
-Supports idea of sub-shells with varied electron energies

Question 12

what is the second ionistion equation is

Answer 12

X+(g) = X2+ (g) +e-

Question 13

describe the reation of oxygen with group2

Answer 13

react with oxygen to produce the metal oxide
2M(s) + O2(g) = 2MO(s)

Question 14

describe the reaction of group 2 as you go down the group

Answer 14

• all the elements react with water to form hydroxides and hydrogen
• with an increase in reactivity down the group
• magnesium reacts slowly , even when the water is heated
• barium reacts rapidly giving a steady stream of hydrogen

M(s) + H2O(l) = M(OH)2 (aq) + H2(g)

Question 15

effect of heating group 2 carbonate

Answer 15

• general formula (MCO3)
• when carbonates are hated, they decompose forming the oxide and releasing carbon dioxide
• MCO3(s) = MO(s) + CO2(g)
• the carbonates becomes more difficult to decompose down the group

Question 16

Compare magnsium carbonate and calcium carbonate

Answer 16

• Magnesium carbonate is easily decomposed by heating in the test tube over a busen burner flame.
• Calcium carbonate needs much stronger heating directly in the flame before it will decompose
• the thermal stabality of CaCO3 is greater than that of MgCO3

Question 17

How does the thermal stability of Group 2 carbonates change going down the group?

Answer 17

• As you go down the group, thermal stability increases
• Means that metals further down decompose at higher temperatures than those further up the group

Question 18

What happens to Group 2 metal carbonates when they are heated?

Give the general equation

Answer 18

Undergo thermal decomposition

Metal carbonate → Metal oxide + Carbon dioxide

MCO3(s) → MO(s) + CO2(g)

Question 19

How does the vigourousnes of Group 2 metals change as you go down the group?

Answer 19

The reactions become more vigorous as you go down the group

Question 20

How do metal hydroxides react with acids?

Answer 20

Metal hydroxide + Acid → Salt + Water

M(OH)2(s/aq) + 2HCl(aq) → MCl2(aq) + 2H2O(l)

Question 21

Why does the thermal stability of Group 2 carbonates increase as you go down the group?

Answer 21

M2+ ions get larger as you go down the group, so their charge density is lower

Because ions higher up the group have greater charge densities, they polarise the carbonate ion more

The more polarised the carbonate ion, the more likely it is to break up + form an oxide ion and CO2

Question 22

What is a polarised ion?

Answer 22

A large (complex) ion that can have its electron distribution altered by small, highly-charged ions

This is known as polarisation

Question 23

What is charge density?

Answer 23

The charge of an ion relative to its size

Mg2+ has a greater charge density than Ba2+ because, although they both have the same overall charge, Mg2+ is smaller