The periodic table is divided into blocks based on the electron configuration of elements. The S-block consists of elements whose last electron enters the outermost s-orbital. This block includes two major groups:
Group 1: Alkali metals
Group 2: Alkaline earth metals
These elements exhibit unique properties due to their electron configuration, leading to significant applications in various industries.
-images-0.jpg "Alkali & Alkaline Earth Metals – Properties, Reactions & Uses")
Understanding the S-Block Elements
What are S-Block Elements?
S-block elements have their outermost electron in the s-orbital. They are found in Group 1 and Group 2 of the periodic table and exhibit highly reactive properties due to their tendency to lose electrons easily.
General Properties of S-Block Elements
- Highly reactive, especially with water and oxygen.
- Good conductors of heat and electricity.
- Form ionic compounds.
- Found mostly in nature as compounds rather than free elements.
Group 1: Alkali Metals
Members of Group 1
- Lithium (Li)
- Sodium (Na)
- Potassium (K)
- Rubidium (Rb)
- Cesium (Cs)
- Francium (Fr) (radioactive)
Why Are They Called Alkali Metals?
Alkali metals react vigorously with water to form hydroxides, which are strongly alkaline in nature.
Electronic Configuration
The general electronic configuration of Group 1 elements is ns¹, meaning they have one electron in their outermost shell.
Key Properties of Alkali Metals
- Highly Reactive: React rapidly with water and oxygen.
- Soft Metals: Can be easily cut with a knife.
- Low Melting and Boiling Points: Due to weak metallic bonding.
- Form Strong Alkaline Hydroxides: Example: Sodium reacts with water to form NaOH.
Reactivity with Water
Alkali metals react with water to form strong bases (hydroxides) and hydrogen gas, often leading to an explosive reaction.
Uses of Alkali Metals
- Lithium: Used in batteries and psychiatric medications.
- Sodium: Used in salt (NaCl), soaps, and street lights.
- Potassium: Essential in fertilizers and explosives.
Group 2: Alkaline Earth Metals
Members of Group 2
- Beryllium (Be)
- Magnesium (Mg)
- Calcium (Ca)
- Strontium (Sr)
- Barium (Ba)
- Radium (Ra) (radioactive)
Why Are They Called Alkaline Earth Metals?
These elements form oxides and hydroxides that are alkaline in nature and are commonly found in the Earth’s crust.
Electronic Configuration
The general electronic configuration of Group 2 elements is ns², meaning they have two valence electrons.
Key Properties of Alkaline Earth Metals
- Less Reactive Than Alkali Metals: But still react with water and acids.
- Harder and Denser: Compared to Group 1 elements.
- Form Alkaline Oxides and Hydroxides: Example:
- Found Abundantly in Nature: As minerals and ores.
Exception: Beryllium (Be)
- Does not behave like typical alkaline earth metals.
- Forms covalent compounds rather than ionic.
- High melting point due to strong covalent bonding.
Uses of Alkaline Earth Metals
- Magnesium: Used in fireworks, medicine, and alloys.
- Calcium: Essential for bones, cement, and glass.
- Barium: Used in medical imaging and fireworks.
Comparison of Group 1 and Group 2 Elements
| Property | Group 1 (Alkali Metals) | Group 2 (Alkaline Earth Metals) |
|---|---|---|
| Valence Electrons | 1 | 2 |
| Reactivity | Very high | Moderate |
| Hardness | Soft | Harder than Group 1 |
| Density | Low | Higher than Group 1 |
| Reaction with Water | Vigorous | Less vigorous |
| Oxide Nature | Strongly basic | Moderately basic |
| Occurrence | Mostly as salts | Found in minerals |
Important Chemical Reactions of S-Block Elements
Reactions of Alkali Metals
- With Water:
- With Oxygen:
- With Halogens:
Reactions of Alkaline Earth Metals
- With Water:
- With Oxygen:
- With Acids:
Applications of S-Block Elements
| Element | Application |
|---|---|
| Lithium | Batteries, psychiatry (mood stabilizers) |
| Sodium | Salt, soap, glass industry |
| Potassium | Fertilizers, fireworks |
| Magnesium | Medicine, fireworks, alloys |
| Calcium | Cement, bones, glass |
| Barium | X-ray imaging, fireworks |
Frequently Asked Questions (FAQs)
Q1: Why are alkali metals stored in kerosene?
Alkali metals react violently with air and water, so they are stored in kerosene to prevent unwanted reactions.
Q2: Which alkali metal is the most reactive?
Francium (Fr) is the most reactive, but due to its radioactive nature, Cesium (Cs) is considered the most reactive stable alkali metal.
Q3: Why is beryllium different from other Group 2 elements?
Beryllium has a small atomic size and high ionization energy, making it covalent rather than ionic. It also does not react with water.
Q4: Why do alkali metals have low melting points?
Alkali metals have weak metallic bonding due to the presence of only one valence electron, making them soft with low melting points.
Q5: How do alkaline earth metals contribute to human health?
- Calcium is crucial for bones and teeth.
- Magnesium is important for muscle and nerve function.
