Group 2

What are alkaline earth metals?

Elements in Group 2 of the Periodic table

What is the trend in melting point as you go down the group?

Melting point decreases

However there is a drop in Mg melting point and then it slightly increases but continues to decrease afterwards

What is the trend in first and second ionisation energy as you go down the group?

Ionisation energies decrease

What is the trend in reactivity as you go down the group?

They get more reactive as you go down

Why does reactivity increase as you go down the group?

The greater shielding effect provided by extra inner shells of electrons

Large distance of outermost electrons from the nucleus outweigh the attraction of higher nuclear charge

How can the increase in reactivity be proven?

Looking at the reaction of the group 2 - Mg to Ba- metals with dilute HCl

As you go down the group the reactions get more vigorous so the rate at which bubbles of hydrogen gas are given off increases

What stops the reactions of Calcium, Strontium or Barium with H2SO4?

An insoluble layer on the surface of the metal forms so the reaction no longer takes place

Slow stream of hydrogen bubbles are produced for a short time until they stop completely

What is the trend in solubility of group 2 sulfates as you go down Group 2?

Solubility decreases

What is formed when a group 2 metal reacts with oxygen?

A Group 2 metal oxide

What is observed when group 2 metals react with oxygen?

* Beryllium only reacts in powdered form
* Magnesium burns with an intense white flame
* Calcium burns with a bright white flame with red at the top
* Strontium is reluctant to burn but then burns intensely with a white flame
* Barium burns with a white flame

What are the flame tests for calcium, strontium and barium ions?

A wire is cleaned with conc. HCL and dipped into the salt to be testes and heated in a non-luminous Bunsen flame

• Calcium compounds - brick red

• Strontium compounds - Scarlet/red

• Barium compounds - Apple green

What happens a when a group 2 oxide reacts with a dilute acid?

A salt and water are formed

MgO + 2HCl → MgCl2 + H2O

How do group 2 elements react with water?

An alkaline hydroxide and hydrogen gas are produced

It is a redox reaction

Why does Beryllium only react with steam at very high temperatures and not with cold water?

Beryllium is the least reactive group 2 metal

How does a group 2 oxide react with water?

The metal hydroxide is formed

What happens with the solutions formed when a group 2 metal oxide reacts with water?

The solutions get more alkaline as you go down the group

What happens when MgO reacts with water?

It is only slightly soluble in water so a weakly alkaline solution of Magnesium hydroxide is formed

What happens when calcium oxide reacts with water?

Calcium hydroxide is formed

It is a vigorous reaction and it releases so much energy that some of the water boils off

What is the trend in solubility of Group 2 hydroxides?

Solubility increases down the group

Which carbonates are insoluble in water?

Magnesium, calcium, strontium and barium carbonates

What happens when group 2 carbonates react with H2SO4?

A salt, water and carbon dioxide are produced

MgCO3 + H2SO4 → MgSO4 + H2O + CO2

Which group 2 sulfate is soluble in water?

MgSO4

What happens when the calcium, strontium and barium carbonates react with water?

An insoluble sulfate layer is formed on the surface of the metals

What happens when group 2 carbonates react with dilute HCl?

Soluble chloride salts, water and carbon dioxide gas are produced

Define thermal decompositoin

The breakdown of a compound by heat into two or more different substances

What is formed when a group 2 carbonate is thermally decomposed?

Metal oxide and carbon dioxide are produced

The temperature at which they are thermally decomposed increases down the group

What is formed when group 2 nitrates are thermally decomposed?

A metal oxide, nitrogen dioxide and oxygen are produced

The temperature at which they are thermally decomposed increases down the group