Alkaline Earth Metals Reactions, Uses, Properties
The general electron configuration of alkaline metals can be defined as [noble gas] ns2 where n represents the valence shell. These metals form +2 cations only. Alkaline earth metals are less reactive than alkali metals.
In this tutorial, we discuss followings of group II elements.
- List of elements of Alkaline earth metals with electron configuration
- Occurrence of Alkaline earth metals
- Chemical properties of Alkaline earth metals
- Uses of alkaline earth metals
List of elements of alkaline earth metals with electron configuration
| Atomic number | Element | Symbol | Electron configuration |
|---|---|---|---|
| 4 | Beryllium | Be | [He] 2s2 |
| 12 | Magnesium | Mg | [Ne] 3s2 |
| 20 | Calcium | Ca | [Ar] 4s2 |
| 38 | Strontium | Sr | [Kr] 5s2 |
| 56 | Barium | Ba | [Xe] 6s2 |
| 88 | Radium | Ra | [Rn] 7s2 |
Occurrence of Alkaline earth metals
Occurrence of Magnesium (Mg)
- As insoluble carbonates, sulphates and silicates in crustal rocks
- About 0.13% in sea water as chloride and sulphate.
Occurrence of Calcium (Ca)
- In vast sedimentary rocks of CaCO3 existing as awhole mountain ranges of limestone, marble and chalk.
- As Gypsum ( CaSO4.2H2O )
- As fluorite (CaF2)
- As fluoroapatite ( 3Ca3(PO4)2.CaF2 )
Chemical properties of Alkaline earth metals
Reactivity of alkaline earth metals varies going down the group. Because metallic characteristics of alkaline earth metals increases when going down the group, reactivity also increases increases going down the group. As an example, Calcium react with water, but magnesium does not. Here, we will discuss following reaction with alkaline earth metals.
- Reactions of water and alkaline earth metals
- Reactions between air and alkaline earth metals
- Alkali earth metals and acids reactions
- Reactions with hydrogen and alkaline earth metals
- Reactions with halogens and alkaline earth metals
- Reactions with ammonia and alkaline earth metals
- Sulfur and alkaline earth metals reactions
- Phosphorous and alkaline earth metal reactions
Reactions of water and alkaline earth metals
Alkaline earth metals react in lesser tendency with water when it compares with alkali metals.
- Beryllium and Magnesium do not react with cold water.
- Magnesium reacts with steam and form magnesium oxide. But beryllium does not react with steam.
- Calcium, strontium and barium react with water and form hydroxides and hydrogen gas. Strontium hydroxide and barium hydroxide are strong bases.
Hydroxides of alkaline earth metals' are basic. Also basic strength increases down the family. As an example, Strontium hydroxide (Sr(OH)2) is more basic than Calcium hydroxide (Ca(OH)2).
Reactions between air and alkaline earth metals
Air contains oxygen gas (O2 and nitrogen gas (N2) as main constituents. Alkaline earth metals reacts with oxygen and nitrogen gases in different ways.
- Due to formation of film of oxides of Beryllium and Magnesium, they do not continuously react with Oxygen gas.
But powdered Beryllium burns and gives Beryllium oxide (BeO) and Beryllium nitride (Be3N2). - When Magnesium burns in air and give a mixture of Magnesium oxide (MgO) and Magnesium nitride (Mg3N2).
- Calcium, strontium and barium easily react with air give respective oxides and nitrides.
- Strontium and Barium can make peroxides with Oxygen gas.
Colours of alkaline earth metal nitrides
| Alkaline metal nitride | Chemical formula | Colour |
|---|---|---|
| Beryllium nitride | Be3N2 | yellow or white powder |
| Magnesium nitride | Mg3N2 | yellow |
| Calcium nitride | Ca3N2 | red-brown |
Alkaline earth metal nitrides and oxygen reaction
Alkaline earth metal nitrides reacts with oxygen and release nitrogen gas and form alkaline earth metal oxides.
Alkaline earth metal nitrides and hydrogen gas reaction
Alkaline earth metal nitrides reacts with hydrogen gas and release ammonia gas and form alkaline earth metal hydride.
Alkali earth metals and acids reactions
In this section, we will look how alkali earth metals react with dilute HCl, dilute H2SO4 and HNO3 acids.
With HCl acid
All alkaline earth metals react with hydrochloric acid (HCl) and give hydrogen gas (H2) and respective salt as products. As an example, Magnesium reacts with HCl and give Magnesium chloride and hydrogen gas as products.
With dilute H2SO4 acid
- Beryllium and Magnesium react with dilute Sulfuric acid and form respective Beryllium sulfate (BeSO4) and Magnesium sulfate (MgSO4). Both BeSO4 and MgSO4 are soluble in water and form colourless aqueous solutions.
- Calcium reacts with sulfuric acid and give Calcium sulfate (CaSO4) and hydrogen gas. Calcium sulfate is sparingly soluble in water. Due to formation of insoluble layer on the metal surface, reaction (or reaction rate) of Calcium and Sulfuric acid will be slow down or stopped.
- Strontium and Barium: These metals react with Sulfuric acid. But Strontium sulfate (SrSO4) and Barium sulfate (BaSO4) are insoluble in water and form white colour precipitates. Therefore, reaction with Sulfuric acid will be much slower or will be completely stopped due to formation of these precipitates
With dilute HNO3 acid
Nitric acid is an oxidizing acid. Therefore, in redox reactions where Nitric acid is involved, oxides of nitrogen (NO and NO2) may be generated. Specifically with metals, Nitric acid gives products as below.
- If Nitric acid concentration is very low, hydrogen gas can be releases as a typical metal - acid reaction.
- If Nitric acid concentration is moderate, Nitric oxide (NO) gas can be releases as a typical metal - acid reaction.
- If concentrated Nitric acid is used, Nitrogen dioxide (NO2) is released.
Let's see how alkaline earth metals react with Nitric acid.
- Beryllium has a strong oxide layer on it's surface. Therefore, reaction of Beryllium with Nitric acid slows down. If oxide layer is removed, reaction rate will be increased.
- Other alkaline earth metals except Beryllium give products according to the concentration of Nitric acid.
Reactions with hydrogen and alkaline earth metals
When alkaline earth metals are heated to high temperature with hydrogen gas, metal hydrides are given. But beryllium and magnesium react very hardly with hydrogen.
Here, hydrogen is reduced to hydride ion and alkaline earth metal is oxidized.
These metal hydrides can emit hydrogen gas when they react with compounds which can supply H+ ions. As an example, when calcium hydride is added to water, calcium hydroxide and hydrogen gas are given as products.
Reactions with halogens and alkaline earth metals
Alkaline earth metals react with halogens and form halides. This reaction is a exothermic reaction.
Ca + Cl2 → CaCl2
Ba + I2 → BaI2
Ammonia and alkaline earth metals
3Mg + 2NH3 → Mg3N2 + H2
Due to release of hydrogen gas, ammonia behaves as an acid.
Sulfur and alkaline earth metals reactions
Mg + H2S → MgS
This metal sulfide reacts with dilute acids and emit hydrogen sulfide gas.
MgS + HCl → MgCl2 + H2S
Phosphorous and alkaline earth metal reactions
Alkaline earth metal phosphide are given when heat is supplied.
3Ca + 2P → Ca3P2
Precipitates of alkaline earth metals with colours
Alkaline earth metal form precipitates with some anions. But, in some cases, all alkaline earth metals from Beryllium to Barium) do not form precipitates with same anion. As an example, Magnesium sulfate is soluble in water, but Barium sulfate is a white precipitate. Precipitates of alkaline earth metals are summarized as below.
Uses of alkaline earth metals
Now we are going to discuss uses of each element in 2nd group.
Uses of beryllium
- For manufacturing of many alloys. As an example, copper beryllium alloys are used in the preparation of high strength springs.
- Metallic beryllium is used for making windows of X-ray tubes.
Uses of magnesium
- Mg is the lightest constructional metal in industry having a density less than two thirds of Al.
- For manufacturing alloying metals.
- For cathodic protection of other metals as oxygen scavenger.
- The compounds of magnesium such as Mg(OH)2 and MgCO3 are used in making tooth pastes.
- Mg is used as a dioxidizer for removing last traces of oxygen from Cu, steel,etc.
Uses of plaster of paris
- for producing moulds for pottery, ceramics, etc
- used for making statues, models and other decorative materials.
- It is used in the building industry as well as plasters.
- In dentistry
- Plaster of paris is used in surgical bandages known as plasters for setting broken and fractured bones in the body because it immoblises the affected part of the organ where there is a bone fracture or sprain.
Physical properties of alkaline earth metals
As physical properties following will be discussed.
- Melting and boiling points
- Density
Melting and boiling points of alkaline earth metals
| Metal | Melting Point (K) | Boiling Point (K) |
|---|---|---|
| Beryllium | 1560 | 2745 |
| Magnesium | 924 | 1363 |
| Calcium | 1124 | 1767 |
| Strontium | 1062 | 1655 |
| Barium | 1002 | 2078 |
| Radium | 973 | 1973 |
Density of alkaline earth metals
| Alkaline earth metal | Density (g cm-3) |
|---|---|
| Beryllium | 1.85 |
| Magnesium | 1.738 |
| Calcium | 1.55 |
| Strontium | 2.64 |
| Barium | 3.51 |
| Radium | 5.0 |
Questions
Compare reaction of alkaline earth metals with oxygen wand alkaline metals with oxygen gas.
Alkali metals reacts more readily and easili with oxygen gas compared to alkaline earth metals because alkali metals eliminate electrons more easily.
Alkaline earth metals react with nitrogen to give?
Alkaline metals react with Nitrogen gas to give respective nitrides.
- Beryllium reacts with nitrogen gas (in the absence of oxygen gas) with supply of heat and give Berrylium nitride which is a yellow to white colour powder.
- Magnesium reacts with nitrogen gas (in the absence of oxygen gas) with supply of heat and give Magnesium nitride (Mg3N2) which is a greenish yellow powder.
- Calcium reacts with nitrogen gas (in the absence of oxygen gas) and give Calcium nitride (Ca3N2) which is a red-brown colour crystalline solid.
what do alkaline earth metals react with?
Alkaline earth metal react with various of other elements and compounds. But sometimes there is a pattern in reactions such as alkaline earth metals and water reaction. Berrylium and Magnesium does not react with water, but Calcium does. Though one alkaline earth metal can react with one compound, but another alkaline earth metal does not react with the same compounds as described here. Generally, we can say that alkaline earth metals react with followings.
- Water
- Acids
- Hydrogen gas
- Nitrogen gas
- Ammonia
- Sulfur
Note that, supplying a higher temperature is required for some reactions.
