🧪 Classification of Elements into s-Block Elements
🌟 s-Block Elements: An Overview
The elements of the periodic table in which the last electron enters the s-orbital are known as s-block elements. The s-orbital can accommodate a maximum of two electrons.
👉 General Electronic Configuration: ns1−2, where n = 1 to 7.
🔷 Group 1 Elements – Alkali Metals
🧪 What Are Group 1 Elements?
Group 1 elements of the periodic table are called Alkali Metals. They are highly reactive metals and are found in the s-block because their outermost electron enters the s-orbital.
👉 General Electronic Configuration: ns1 (where n = 2 to 7)
🌟 List of Group 1 Elements
| Element | Symbol | Atomic Number | Physical State | Appearance |
|---|---|---|---|---|
| Lithium | Li | 3 | Solid | Silvery-white |
| Sodium | Na | 11 | Solid | Silvery-white |
| Potassium | K | 19 | Solid | Silvery-grey |
| Rubidium | Rb | 37 | Solid | Silvery-grey |
| Cesium | Cs | 55 | Liquid (near room temperature) | Golden |
| Francium | Fr | 87 | Liquid (radioactive) | Unknown (highly unstable) |
⚙️ Important Properties of Group 1 Elements
- 💥 Highly reactive, especially with water.
- 🌡️ Low melting and boiling points (compared to other metals).
- ⚖️ Soft metals – can be cut with a knife.
- 📈 Reactivity increases down the group.
- 💧 React with water to form alkalies (strong bases) and hydrogen gas.
- 🧪 Form colorless ionic compounds.
🔬 Reaction with Water
$$\text{2Na + 2H}_2\text{O} \rightarrow 2NaOH + H_2 \uparrow$$
This reaction produces:
- Alkali (NaOH) – a strong base
- Hydrogen gas – burns with a ‘pop’ sound
📌 Trends in Group 1 Elements
| Property | Trend Down the Group |
|---|---|
| Atomic Radius | Increases |
| Ionization Energy | Decreases |
| Metallic Character | Increases |
| Density | Increases (except K < Na) |
| Melting and Boiling Points | Decrease |
💡 Quick Facts
- 🟡 Cesium is a liquid near room temperature and has a golden glow.
- ☢️ Francium is radioactive and extremely rare.
- 🧪 All alkali metals form +1 ions (M⁺+) in reactions.
- 🚫 Must be stored under kerosene/oil to prevent oxidation.
🧠 Do You Know?
- 🔋 Lithium is used in rechargeable batteries.
- 🍽️ Sodium compounds like NaCl (common salt) are essential in our diet.
- 🚀 Potassium nitrate (KNO3) is a component in gunpowder.
- ⚡ Cesium clocks are used in atomic timekeeping.
🔷 Group 2 Elements – Alkaline Earth Metals
🧪 What Are Group 2 Elements?
Group 2 elements of the periodic table are called Alkaline Earth Metals. These elements belong to the s-block as their outermost electron enters the s-orbital, specifically with the configuration ns².
👉 General Electronic Configuration: ns2 (where n = 2 to 7)
🌟 List of Group 2 Elements
| Element | Symbol | Atomic Number | Physical State | Appearance |
|---|---|---|---|---|
| Beryllium | Be | 4 | Solid | Steel-grey |
| Magnesium | Mg | 12 | Solid | Silvery-white |
| Calcium | Ca | 20 | Solid | Silvery-white |
| Strontium | Sr | 38 | Solid | Silvery-grey |
| Barium | Ba | 56 | Solid | Silvery-white |
| Radium | Ra | 88 | Solid | Silvery-white (Radioactive) |
⚙️ Key Properties of Group 2 Elements
- ⚗️ Less reactive than Group 1 but still reactive, especially with water and acids.
- 🔥 Burn in air to form oxides.
- 💧 Oxides are basic and sparingly soluble in water — hence the name alkaline.
- 🧱 Commonly found in earth’s crust as minerals and ores.
- ⚖️ Form divalent ions (M2+) in compounds.
🧪 Reactions of Group 2 Elements
With Water (except Be): $$\text{Ca + 2H}_2\text{O} \rightarrow \text{Ca(OH)}_2 + \text{H}_2 \uparrow$$
- Forms alkaline hydroxides.
- Beryllium does not react with water due to formation of a passive oxide layer.
With Oxygen: $$2Mg + O_2 \rightarrow 2MgO$$
- Forms white metal oxides that are basic in nature.
📊 Trends in Group 2 Elements
| Property | Trend Down the Group |
|---|---|
| Atomic Radius | Increases |
| Ionization Energy | Decreases |
| Reactivity | Increases |
| Melting and Boiling Points | Decrease |
| Solubility of Hydroxides | Increases |
💡 Quick Facts
- ⚠️ Radium (Ra) is radioactive and was once used in luminous paints.
- 💊 Magnesium hydroxide is used as an antacid (milk of magnesia).
- 🏗️ Calcium compounds like CaCO₃ are found in chalk, marble, and limestone.
- 🚫 Beryllium is toxic and has covalent character in its compounds.
🧠 Do You Know?
- 🧪 Magnesium burns with a bright white flame, used in fireworks and flares.
- 🦴 Calcium is essential for bones and teeth in the human body.
- 💡 Barium sulfate is used in X-ray imaging of the digestive tract.
- 🪦 Radium was discovered by Marie Curie and is a source of radiation.
🔹 Group 1 and Group 2 Elements
- ✅ Group 1 Elements are known as Alkali Metals.
💧 They react with water to form alkalies (basic solutions). - ✅ Group 2 Elements are known as Alkaline Earth Metals.
🌱 Their oxides also form alkalies with water and are commonly found in the earth’s crust.
📊 Key Characteristics of s-Block Elements
| Property | Description |
|---|---|
| 🧬 Electron Configuration | Ends in ns1 or ns2 |
| 📦 Total Number | 14 s-block elements in total |
| ☢️ Radioactive Elements | Francium (Fr-87) and Radium (Ra-88) |
| 🌬️ Gaseous Elements | Hydrogen (H) and Helium (He) |
| 💧 Liquid Elements | Cesium (Cs) and Francium (Fr) are liquid at or near room temperature |
💡 Quick Facts to Remember
- 🌍 Alkaline earth metals are called so because they are found in earth’s crust and their oxides form alkalies.
- 🌊 Alkali metals react vigorously with water.
- 🔬 Francium and Radium are radioactive.
- 🧊 Hydrogen and Helium are gaseous at room temperature.
- 🧪 Cesium and Francium are liquid s-block elements.
🧠 Do You Know?
- Francium is the most electropositive element in the periodic table.
- Helium, though placed in group 18 due to its inert nature, electronically belongs to the s-block.
- Cesium has a melting point of just 28.5°C, which is why it’s liquid in hot climates.
📘 Conclusion
s-Block elements are essential to understanding the periodic classification. From the lightest gas hydrogen to the radioactive Francium, they showcase a wide range of chemical and physical properties that play a vital role in modern chemistry.
✅ Tags: s-block elements, periodic table, alkali metals, alkaline earth metals, chemistry class 11, NEET, JEE
📚 Category: Class 11 Chemistry, Periodic Classification
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