Grade 11 → S-block elements (alkali and alkaline earth metals) ↓
Group 2 Elements - Properties and Trends
The elements in group 2 of the periodic table are known as the alkaline earth metals. These include the elements beryllium (Be
), magnesium (Mg
), calcium (Ca
), strontium (Sr
), barium (Ba
) and radium (Ra
). They are found in the second column of the periodic table and have some unique properties and trends that make them an interesting subject for study in chemistry.
General properties of group 2 elements
The elements in group 2 have a number of properties that are quite different from those in the other groups:
- Valence electrons: All the elements in group 2 have two electrons in their outermost shell, due to which their valency is +2.
- Oxidation state: They form compounds mainly in +2 oxidation state.
- Metallic properties: They are all metals and show typical metallic properties, such as good electrical and thermal conductivity, malleability and ductility.
- Density: Group 2 metals are denser than the alkali metals of Group 1.
- Melting point and boiling point: Their melting point and boiling point are generally higher than those of alkali metals.
Chemical reactions of group 2 elements
Group 2 elements react with many other elements and compounds. Here are some common reactions:
Reaction with water
The alkaline earth metals react readily with water, although not as vigorously as the Group 1 elements. The typical reaction with water is as follows:
M + 2H2O → M(OH)2 + H2
where M
represents a Group 2 element. For example, the reaction of magnesium with water produces magnesium hydroxide and hydrogen gas:
Mg + 2H2O → Mg(OH)2 + H2
Reaction with oxygen
Group 2 elements react with oxygen to form metal oxides. The general equation for this reaction is:
2M + O2 → 2MO
For example, calcium oxide is formed as a result of the reaction between calcium and oxygen:
2Ca + O2 → 2CaO
Trends in group 2 elements
Moving down the group from beryllium to radium, there are noticeable trends in the properties of the elements:
Atomic and ionic size
Atomic and ionic radii increase as you move down a group. This increase is due to the addition of electron shells as you move from one period to the next.
Visual example:
Ionization energy
Ionization energy decreases going down the group. This is due to the increasing distance of the outer electrons from the nucleus and the increase in the electron shielding effect, which makes it easier to remove an electron.
Visual example:
Jet
The reactivity of the alkaline earth metals increases going down the group. This is due to a decrease in ionization energy, making it easier for atoms to lose electrons and participate in reactions.
Uses of group 2 elements
Group 2 elements have a wide range of applications due to their unique properties:
- Beryllium: Because of its strength and low mass, it is used in aerospace components and as a moderator in nuclear reactors.
- Magnesium: It is commonly used in the manufacture of lighter materials, and as an ingredient in fireworks and flares.
- Calcium: Important in biological systems and widely used in the construction industry in the form of limestone and cement.
- Strontium: Used in the production of glass for color television cathode ray tubes and for red color in fireworks.
- Barium: Used in oil and gas drilling fluids, and in medical imaging because of its contrast properties.
Biological importance of group 2 elements
Calcium and magnesium, in particular, play important roles in biological systems:
- Calcium: Essential for bone and teeth health, muscle function and nerve signalling.
- Magnesium: Important for enzyme function and energy production in cells.
Conclusion
The elements of group 2 are fascinating in the field of chemistry because of their physical and chemical properties, the trends observed as we move down the group, and their diverse applications in various industries and biological systems. Understanding these elements helps us understand both the complexity and utility of the periodic table in practical and theoretical chemistry.