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# Group 2 Compounds

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Group 2 metals, also known as alkaline earth metals, have the ability to form a wide range of compounds with a wide range of uses. From chemical analysis to medical diagnosis, these compounds have several uses in daily life. But how do these compounds form, and why do their chemical properties make them suitable for such uses?

• Firstly, we will look at what group 2 elements are, and summarise their properties.
• After that, we will look at some key examples of group 2 compounds to get an idea of what they are.
• Then, we shall explore the reactions of group 2 compounds with water and acid.
• We will then look into the solubility of group 2 compounds.
• Finally, we will outline some of the uses of group 2 compounds.

## What Are Group 2 elements?

Group 2 elements also known as the 'alkaline earth metals' are a part of the s-block on the periodic table, having two electrons in the outermost shell. When the metal atoms react to form ions, they lose the two outer electrons and form 2+ ions.

Periodic table highlighting the group 2 metals. Sahraan Khowaja, StudySmarter Originals.

### Properties of group 2

· Group 2 elements have two electrons in their outer shell and these electrons are found in the outer s-orbital.

· When these group 2 elements react, they lose their outer electrons and gain a charge of 2+.

· The melting points of group 2 elements generally decrease as you go down the group.

· First ionisation energy decreases as you go down group 2.

· Electronegativity also decreases as you go down group 2.

· The reactivity of group 2 elements increases as you go down the group.

### What are group 2 compounds?

Elements of group 2 can form compounds that form when elements are combined together. Let's recall some common group 2 compounds.

Calcium hydroxide, Ca(OH)2, is one well-known example. Calcium hydroxide is a colourless crystal produced by mixing water and quicklime.

Magnesium carbonate, MgCO3, is another example. This is a white solid and a lot of its forms exist as minerals.

Strontium oxide, SrO, is formed by the reaction between strontium and oxygen. This compound is useful in ceramic applications.

### Reactions of group 2 elements

#### With water

• The metals magnesium to barium react with water.
• Beryllium does not react with water.

Magnesium reacts with steam to produce magnesium oxide.

Mg(s) + H2O(g) —› MgO(s) + H2(g)

Magnesium reacts extremely slowly with cold water producing magnesium hydroxide.

Mg(s) + 2H2O(l) —› Mg(OH)2(aq) + H2(g)

The rest of the group 2 metals are able to react with cold water and form metal hydroxides and hydrogen.

Observations:

• the metal dissolving and it dissolves faster going down the group
• fizzing
• the solution heating up
• with calcium, the solution becomes more saturated, and a white precipitate forms.

The oxides of group 2 metals are basic oxides apart from beryllium oxide. They react with water to form metal hydroxides and the solutions are strongly alkaline due to the hydroxide ions (OH-).

For example:

CaO(s) + H20(l) —› Ca(OH)2(aq)

The hydroxides of group 2 elements magnesium to barium are soluble in water and form alkaline solutions. The solutions are strongly alkaline due to the presence of the hydroxide ions, OH-. The products of this reaction always has the same formula of M(OH)2, where M is a Group 2 metal.

The carbonates of the group 2 metals are insoluble in water except for BeCO3.

#### With Acid

The oxides of group 2 metals react with acids to form salts.

An example of this is:

CaO(s) + 2HNO3(aq) —› Ca(NO3)2(aq) + H2O(l)

This equation shows calcium oxide reacting with dilute nitric acid, producing calcium nitrate and water.

When group 2 hydroxides react with dilute acids then the product is a colourless solution of metal salts.

An example of this is:

Ca(OH)2(aq) + 2HCl(aq) —› CaCl2(aq) + 2H2O(l)

The group 2 carbonates react with dilute acid to produce a salt, water and carbon dioxide. For example,

${\mathrm{MgCO}}_{3}+2\mathrm{HCl}\to {\mathrm{MgCl}}_{2}+{\mathrm{H}}_{2}\mathrm{O}+{\mathrm{CO}}_{2}$

The group 2 carbonates decompose when heated to form the oxide and carbon dioxide.

An example of this is:

CaCO3(s) —› CaO(s) + CO2(g)

### Solubility of Group 2 Compounds

#### Solubility of hydroxides

The group 2 hydroxides become more soluble as you go down the group. Due to this, the pH of the solution increases as the concentration of the OH- ions increases.

An equation that represents the hydroxide dissolving in water is:

X(OH)2(aq) —› X2+(aq) + 2OH-(aq)

In this instance, the X represents a group 2 element.

#### Solubility Of Sulphates

As you go down group 2, the solubility of the sulfates decreases. Magnesium is the most soluble in the group and barium is the least which makes it insoluble.

### Uses Of Group 2 Compounds

Let’s talk about some uses of common group 2 compounds.

Magnesium oxide is a white solid and can be used as a heat-resistant ceramic to line furnaces due to its very high melting temperature. Magnesium oxide turns to magnesium hydroxide in water.

Since magnesium hydroxide is insoluble in water, it is the active ingredient in milk of magnesia, used as an antacid and laxative.

Calcium hydroxide forms an alkaline solution as it is slightly soluble in water and the alkaline solution is normally called limewater.

Barium hydroxide is sometimes used as an alkali in chemical analysis.

Barium sulfate (BaSO4) is insoluble and is used in medicine. It absorbs X-rays strongly and is used to diagnose disorders of the intestines and stomach. Due to its insolubility, it is not absorbed into the bloodstream from the gut.

Calcium hydroxide, Ca(OH)2, is used in agriculture in order to increase the pH of soil.

Calcium oxide, CaO, can be used to remove SO2 from flue gases. SO2 is formed when fossil fuels are burnt to produce electricity.

Acidified barium chloride, BaCl2, is used to test for sulfate ions. This is done by adding dilute hydrochloric acid to the solution followed by barium chloride solution. If a white precipitate is formed, then this shows that the sulfate ions are present in the compound.

## Group 2 Compounds - Key takeaways

• When the group 2 metal atoms react to form ions, they lose the two outer electrons and form 2+ ions.
• Elements of group 2 can form compounds that form when elements are combined together.
• Beryllium does not react with water, but the rest of the group 2 metals are able to react with cold water and form metal hydroxides and hydrogen gas.
• The oxides of group 2 metals react with acids to form salts.
• The group 2 hydroxides become more soluble as you go down the group.
• The group 2 sulfates become less soluble as you go down the group.
• Barium sulfate (BaSO4) is insoluble and therefore has uses in the medical sector.

## Group 2 Compounds

When the group 2 metals react to form ions, they lose the two outer electrons and form 2+ ions. Elements of group 2 can form compounds when elements are combined together.

Barium sulfate (BaSO4), which is insoluble, is used in medicine. It absorbs X-rays strongly and is used to diagnose disorders of the intestines and stomach. Due to its insolubility, it is not absorbed into the bloodstream from the gut.

Magnesium hydroxide is the active ingredient in milk of magnesia, which is used as an antacid and laxative.

- The group 2 hydroxides become more soluble as you go down the group.

- The group 2 sulfates become less soluble as you go down the group.

-  The oxides of group 2 metals are basic oxides apart from beryllium oxide.

- The oxides of group 2 metals react with water to form metal hydroxides which are strongly alkaline solutions.

- The carbonates of the group 2 metals are insoluble in water except for BeCO3.

-The oxides of group 2 metals react with acids to form salts.

- The oxides of group 2 metals, apart from beryllium oxide, react with water to form metal hydroxides.

- The oxides of group 2 metals react with acids to form salts.

- Group 2 hydroxides react with dilute acids. The product is a colourless solution of metal salts.

- The group 2 carbonates decompose when heated to form the oxide and carbon dioxide.

## Final Group 2 Compounds Quiz

Question

What are group 2 elements?

Group 2 elements also known as the 'alkaline earth metals' are a part of the s-block on the periodic table, having two electrons in the outermost shell.

Show question

Question

What are the properties of group 2 elements?

-  The melting points of group 2 elements generally decrease as you go down the group.

- The reactivity of group 2 elements increases as you go down the group.

-  When these group 2 elements react, they lose their outer electrons and gain a charge of 2+.

Show question

Question

What are some common group 2 compounds?

- Calcium hydroxide, Ca(OH)2

- Magnesium carbonate, MgCO3

- Strontium oxide, SrO

Show question

Question

Which group 2 element does not react with water?

Beryllium

Show question

Question

What does magnesium produce upon reaction with steam?

Magnesium reacts with steam to produce magnesium oxide.

Mg(s) + H2O(g) —› MgO(s) + H2(g)

Show question

Question

What does magesium produce upon reaction with cold water?

Magnesium reacts extremely slowly with cold water producing magnesium hydroxide.

Mg(s) + 2H2O(l) —› Mg(OH)2(aq) + H2(g)

Show question

Question

What are the observations when group 2 elements react with cold water?

- The metal dissolves. It dissolves faster going down the group.

- Fizzing

- The solution heats up.

- With calcium, the solution becomes more saturated, and a white precipitate forms.

Show question

Question

What do the oxides of group 2 metals produce when reacted with acid?

- Salts

For example,

CaO(s) + 2HNO3(aq) —› Ca(NO3)2(aq) + H2O(l)

This equation shows calcium oxide reacting with dilute nitric acid, producing calcium nitrate and water.

Show question

Question

What is the solubility of group 2 hydroxides?

The group 2 hydroxides become more soluble as you go down the group.

Show question

Question

What is the solubility of group 2 sulfates?

As you go down group 2, the solubility of the sulfates decreases.

Show question

Question

What do group 2 carbonates produce when reacted with dilute acid?

The group 2 carbonates react with dilute acid to produce a salt, water and carbon dioxide.

Show question

Question

What do group 2 hydroxides produce when reacted with dilute acids?

When group 2 hydroxides react with dilute acids, the product is a colourless solution of metal salts.

An example of this is:

Ca(OH)2(aq) + 2HCl(aq) —› CaCl2(aq) + 2H2O(l)

Show question

Question

Which group 2 oxide is not a basic oxide?

Beryllium oxide

Show question

Question

Are hydroxides of group 2 elements soluble ?

The hydroxides of group 2 elements from magnesium to barium are soluble in water and form alkaline solutions.

Show question

Question

What is the use of barium sulfate (BaSO4)?

It is insoluble and is used in medicine. It absorbs X-rays strongly and is used to diagnose disorders of the intestines and stomach. Due to its insolubility, it is not absorbed into the bloodstream from the gut.

Show question

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