Elements of Groups 1, 2 and 13 to 18
Easy Overview
Not all elements in the periodic table are equally popular. This chapter is about the s-block (groups 1 and 2) and p-block (groups 13 to 18) elements. These are the elements that make up most of the Earth's crust, your body, and the air you breathe. From the explosive reactivity of alkali metals to the laziness of noble gases — it's all here.
Alkali Metals (Group 1) — The Drama Queens
Lithium, sodium, potassium, and friends all have one electron in their outer shell that they desperately want to get rid of. They're the most reactive metals. Drop sodium in water and it fizzes and zips around. Drop potassium and it catches fire. They react with water to form alkalis (hence the name) and hydrogen gas. Store them under oil or they'll react with air moisture.
Alkaline Earth Metals (Group 2)
These have two electrons to lose, so they're less reactive than Group 1 but still pretty reactive. Magnesium burns with a blinding white light (flashbulbs use this). Calcium is essential for bones. Beryllium is surprisingly unreactive — the odd one out. Their compounds are often found in rocks and minerals.
Boron Family (Group 13)
Boron is a metalloid (kinda metal, kinda not). Aluminum is everywhere — foil, cans, airplanes. Gallium melts in your hand. Thallium is toxic. The trend: as you go down, metallic character increases. Boron is non-metallic, aluminum is metallic, and by the time you reach thallium, it's fully metallic.
Carbon Family (Group 14)
Carbon is the king of life — it forms more compounds than all other elements combined. Silicon is the basis of computer chips. Germanium is used in electronics. Tin makes bronze. Lead was used in pipes (bad idea). The key pattern: carbon forms strong double/triple bonds; silicon and below prefer single bonds.
Nitrogen and Oxygen Families (Groups 15 and 16)
Nitrogen makes up 78% of air but N≡N is so stable it's hard to break. Phosphorus catches fire in air. Oxygen keeps us alive. Sulfur smells like rotten eggs. The reactivity and properties change dramatically as you go down these groups.
Halogens and Noble Gases (Groups 17 and 18)
Halogens are one electron short of a full shell — they desperately want one more. Fluorine is the most reactive element known. Chlorine is used to disinfect water. Iodine is needed for your thyroid. Noble gases already have a full shell — they don't want anything. They're the introverts of the periodic table.
Key Points
- •Alkali metals (Group 1): ns¹, highly reactive, form +1 ions, stored under oil
- •Alkaline earth metals (Group 2): ns², less reactive than Group 1, form +2 ions
- •Halogens (Group 17): ns²np⁵, highly reactive non-metals, form -1 ions
- •Noble gases (Group 18): ns²np⁶, inert due to full valence shell
- •Metallic character increases down a group in p-block
- •Carbon can form catenated compounds (long chains) — unique in Group 14
- •Reactivity of halogens decreases down the group: F₂ > Cl₂ > Br₂ > I₂
- •Noble gases were once called 'inert gases' but some compounds like XeF₂ exist
Practice Questions
- Why are alkali metals stored under kerosene? What happens when sodium reacts with water?
- Explain the trend in reactivity of halogens down the group.
- What are the anomalous properties of lithium compared to other alkali metals?
- Why is carbon able to form such a huge number of compounds?
- Describe the preparation and uses of bleaching powder (CaOCl₂).