Summary & Quick Quiz അലോഹങ്ങൾ
The whole chapter on one page: the five non-metals in seven pictures, a facts & rules card for each – how it is made, how it is tested, its properties and its uses – the gas tests at a glance, calorific values with a fuel calculator, the allotropes of carbon, every key reaction with an atom counter, fertilisers, the mistakes to avoid, flashcards, a scored quiz and your study checklist.
1. The chapter in seven pictures
🗺️ From the periodic table to bleaching powder
2. Facts & rules card – one per non-metal
H, C, N and O are in periods 1 and 2; chlorine (2, 8, 7) is a halogen in group 17. Non-metals are dull (except graphite and iodine), brittle when solid, and poor conductors of heat and electricity (except graphite). Many of them exist as diatomic molecules (ദ്വയാറ്റോമിക തന്മാത്ര): H2, N2, O2, Cl2.
H Hydrogen ഹൈഡ്രജൻ
- Facts
- Z = 1; 1 electron, 1 proton, 0 neutrons (protium). Isotopes (ഐസോടോപ്പുകൾ): protium, deuterium, tritium. Most abundant element in the universe; very little free in air. Discovered by Henry Cavendish in 1766 – “inflammable air” (കത്തുന്ന വായു).
- Lab
- Zn + 2HCl → ZnCl2 + H2 (zinc + dilute HCl, Fig 7.1)
- Industry
- 2H2O electrolysis 2H2 + O2
- Test
- a burning splinter at the mouth – the gas burns with a “pop” (പോപ്പ് ശബ്ദം)
- Properties
- colourless, odourless, does not dissolve in water, less dense than air, diatomic, burns explosively
- Reactions
- 2H2 + O2 → 2H2O + heat; H2 + Cl2 sunlight 2HCl – both combination reactions
- Uses
- making ammonia and methanol (CH3OH); fuel; saturated oils such as vanaspati (പൂരിത എണ്ണകൾ); reducing agent (നിരോക്സീകാരി) to get metals from oxides
C Carbon കാർബൺ
- Facts
- Z = 6; 2, 4; group 14, period 2; valency 4.
- Allotropes
- Crystalline (ക്രിസ്റ്റലീയ): diamond, graphite, graphene, fullerene. Amorphous (അമോർഫസ്): charcoal, coke, lamp black, coal – see the table below.
- Burning
- C + O2 → CO2 (enough oxygen); 2C + O2 → 2CO (excess carbon / too little oxygen)
CO₂ Carbon dioxide & carbon monoxide
- Lab
- CaCO3 + 2HCl → CaCl2 + H2O + CO2 (marble chips + dilute HCl, thistle funnel തിസിൽ ഫണൽ, Fig 7.8)
- Test
- clear lime water (ചുണ്ണാമ്പുവെള്ളം) turns milky
- Properties
- colourless, odourless, denser than air, does not support combustion, its solution in water is acidic (carbonic acid കാർബോണിക് ആസിഡ്, H2CO3)
- Uses
- fire extinguishers (അഗ്നിശമനികൾ); soda water and soft drinks; washing soda Na2CO3·10H2O and baking soda NaHCO3; urea; carbogen (O2 95 % + CO2 5 %); dry ice (ഡ്രൈ ഐസ്) for stage “smoke”
- CO
- poisonous: with haemoglobin it forms carboxyhaemoglobin (കാർബോക്സീഹീമോഗ്ലോബിൻ) and blood carries less oxygen. Uses: gaseous fuel, water gas (CO + H2), producer gas (CO + N2), reducing agent.
- Carbonate test
- salt solution + BaCl2 → white precipitate; + dilute HCl → it dissolves with effervescence (CO2) → a carbonate
N Nitrogen നൈട്രജൻ
- Facts
- 78 % of air – the largest share; in all living things; essential for plant growth. Inert (നിഷ്ക്രിയം) because of the strong triple bond N≡N. It dilutes oxygen and so helps control combustion.
- Lightning
- N2 + O2 lightning 2NO; then 2NO + O2 → 2NO2; then 4NO2 + 2H2O + O2 → 4HNO3 → nitrates in the soil
- Fixation
- Rhizobium bacteria in the root nodules of pulse plants (payar) – nitrogen fixation (നൈട്രജൻ സ്ഥിരീകരണം)
- Properties
- colourless, odourless, very slightly soluble in water, hard to liquefy
- Uses
- ammonia (N2 + 3H2 → 2NH3) and nitrogenous fertilisers; liquid nitrogen as a coolant (ശീതീകാരി); filling tyres; food packets (keeps out oxygen)
O Oxygen & ozone പ്രാണവായു
- Facts
- Most abundant element in the Earth’s crust; the “life gas”. Discovered by Joseph Priestley in 1774; named by Lavoisier (“acid-producer”).
- Lab
- 2KMnO4 heat K2MnO4 + MnO2 + O2 (Fig 7.9, teacher only)
- Test
- a glowing splinter bursts into flame – a supporter of combustion (ജ്വലനസഹായി)
- Properties
- colourless, odourless, slightly soluble in water (enough for fish), does not burn but helps burning; forms oxides with metals and non-metals – C + O2 → CO2, 2H2 + O2 → 2H2O; metals slowly lose their shine
- Uses
- supports combustion; oxidiser in rocket fuels; artificial respiration; oxy-acetylene welding
- Ozone
- O3, mostly in the stratosphere: O2 UV 2O, O2 + O → O3; overall 3O2 UV⇌ 2O3. It absorbs harmful UV (അൾട്രാവയലറ്റ് വികിരണങ്ങൾ); it is also a greenhouse gas (ഗ്രീൻ ഹൗസ് വാതകം). CFCs (ക്ലോറോഫ്ലൂറോകാർബണുകൾ) release chlorine that destroys it – ozone layer depletion. Substitutes: HFCs, liquid hydrocarbons, ammonia, solid CO2. Ozone Day: 16 September.
Cl Chlorine ക്ലോറിൻ
- Facts
- Table 7.6: Z = 17; 2, 8, 7; mass number 35; 17 electrons, 18 neutrons; valency 1; a halogen. Very reactive – never found free.
- Lab
- 2KMnO4 + 16HCl → 2KCl + 2MnCl2 + 8H2O + 5Cl2 (KMnO4 + concentrated HCl, Fig 7.10 – teacher only, fume cupboard). Water removes HCl vapour; concentrated H2SO4 removes water vapour; collected by upward displacement of air.
- Properties
- greenish-yellow, pungent smell, denser than air, poisonous
- Bleaching
- dry cloth – no change; moist cloth – colour fades: H2O + Cl2 → HCl + HOCl, HOCl → HCl + [O]. Nascent oxygen (നവജാത ഓക്സിജൻ) oxidises coloured substances to colourless ones.
- Bleaching powder
- 2Ca(OH)2 + 2Cl2 → Ca(OCl)2 + CaCl2 + 2H2O (ബ്ലീച്ചിങ് പൗഡർ)
- Chloride test
- NaCl + AgNO3 → AgCl + NaNO3 – curdy white AgCl; it dissolves in NH4OH → chloride
- Uses
- bleaching; antiseptics and pesticides (കീടനാശിനി); disinfectant (അണുനാശിനി) for drinking water and wells
Organic manure or chemical fertiliser? (Table 7.4) ജൈവവളം · രാസവളം
| Organic manure | Chemical fertiliser |
|---|---|
| eco-friendly | gives more yield |
| keeps the natural character of the soil | easily available |
| gives nutrients slowly | gives the three nutrients (N, P, K) quickly |
| does not harm micro-organisms | changes the living make-up of the soil |
| needed in larger amounts | increases the acidity of the soil |
| less chance of pollution | causes pollution |
The textbook’s conclusion: use fertilisers in a scientific, sensible way.
3. The tests at a glance
| Substance | Test | What you see |
|---|---|---|
| hydrogen | burning splinter at the mouth of the tube | the gas burns with a “pop” |
| oxygen | glowing splinter put in | it bursts into flame |
| carbon dioxide | pass the gas through clear lime water | lime water turns milky |
| chlorine | moist coloured cloth (smell only from a distance!) | the colour fades; greenish-yellow gas, pungent smell |
| carbonate | BaCl2 solution, then dilute HCl to the precipitate | white precipitate that dissolves with effervescence |
| chloride | AgNO3 solution, then NH4OH | curdy white precipitate that dissolves |
4. Calorific value ഇന്ധനം · കലോറിക മൂല്യം
The calorific value of a fuel is the heat energy released when unit mass (1 g) of it burns completely – in kJ/g. So heat = mass × calorific value. Hydrogen is the best by far, and burning it gives only water – but it burns explosively and is hard to store and transport.
🔥 Fuel calculator (Fig 7.2 values)
5. Allotropes of carbon രൂപാന്തരങ്ങൾ · രൂപാന്തരത്വം
🔑 Key box (p. 137)
Different forms of the same element with different physical properties are allotropes; the phenomenon is allotropy.
Crystallinediamond · graphite · graphene · fullerene
Amorphouscharcoal · coke · lamp black (വിളക്കുകരി) · coal
| Diamond വജ്രം | Graphite ഗ്രാഫൈറ്റ് | Graphene ഗ്രഫീൻ | Fullerene ഫുള്ളറീൻ | |
|---|---|---|---|---|
| Structure | 3-D network | layers of hexagons held by weak forces | one layer of graphite | hollow spheres (buckyballs) or tubes (buckytubes) of pentagons and hexagons |
| Each C bonded to | 4 carbon atoms | 3 carbon atoms | 3 carbon atoms | 3 carbon atoms |
| Free electrons | none | one per carbon atom | yes | not studied in Class 9 |
| Electricity | does not conduct | conducts | conducts very well | not studied in Class 9 |
| Key properties | hardest natural substance; high thermal conductivity (താപചാലകത); high refractive index (അപവർത്തനാങ്കം) – it sparkles | soft, slippery – the layers slide | extremely thin and light; high electrical and thermal conductivity | buckyballs (ബക്കിബോൾസ്), buckytubes (ബക്കിട്യൂബ്സ്) |
| Uses | jewellery, cutting glass | dry-cell electrodes, pencil “lead”, lubricant (സ്നേഹകം) | nanotechnology (നാനോടെക്നോളജി) | nanotechnology |
6. Key reactions and an atom counter
Every equation of the chapter, balanced. To balance, change only the numbers in front of the formulas, never the small numbers inside them, until each element has the same number of atoms on both sides.
| Equation | What it shows | Learn it on |
|---|---|---|
| Zn + 2HCl → ZnCl2 + H2 | laboratory preparation of hydrogen (Fig 7.1) | page 3 |
| 2H2O electrolysis 2H2 + O2 | industrial preparation of hydrogen and oxygen | page 3 |
| 2H2 + O2 → 2H2O | hydrogen burns – combination (gives heat; only water forms) | page 3 |
| H2 + Cl2 sunlight 2HCl | combination | page 3 |
| C + O2 → CO2 | carbon burns in enough oxygen | page 6 |
| 2C + O2 → 2CO | excess carbon or too little oxygen – poisonous CO | page 6 |
| CaCO3 + 2HCl → CaCl2 + H2O + CO2 | laboratory preparation of carbon dioxide (Fig 7.8) | page 6 |
| N2 + O2 lightning 2NO | lightning – step 1 | page 7 |
| 2NO + O2 → 2NO2 | lightning – step 2 | page 7 |
| 4NO2 + 2H2O + O2 → 4HNO3 | nitric acid reaches the soil as nitrates | page 7 |
| N2 + 3H2 → 2NH3 | ammonia for fertilisers (FACT) | page 7 |
| 2KMnO4 heat K2MnO4 + MnO2 + O2 | laboratory preparation of oxygen (Fig 7.9) | page 8 |
| O2 UV 2O | ozone cycle – UV splits oxygen | page 8 |
| O2 + O → O3 | ozone cycle – ozone forms | page 8 |
| 3O2 UV⇌ 2O3 | the overall ozone–oxygen cycle | page 8 |
| 2KMnO4 + 16HCl → 2KCl + 2MnCl2 + 8H2O + 5Cl2 | laboratory preparation of chlorine (Fig 7.10) – teacher only | page 9 |
| H2O + Cl2 → HCl + HOCl | chlorine in water – hypochlorous acid | page 9 |
| HOCl → HCl + [O] | nascent oxygen – it bleaches | page 9 |
| 2Ca(OH)2 + 2Cl2 → Ca(OCl)2 + CaCl2 + 2H2O | manufacture of bleaching powder | page 9 |
| NaCl + AgNO3 → AgCl + NaNO3 | test for a chloride – curdy white AgCl | page 9 |
⚖️ Atom counter
⚠️ Common mistakes
- Testing hydrogen with a glowing splinter. That is the oxygen test. Hydrogen burns with a “pop” at a burning splinter.
- Saying carbon dioxide supports burning. It puts fires out – that is why it is in fire extinguishers.
- Saying diamond conducts electricity because it is carbon, or that graphite does not. Diamond has no free electrons; graphite has one free electron per atom and conducts.
- Mixing up washing soda (Na2CO3·10H2O) and baking soda (NaHCO3), or water gas (CO + H2) and producer gas (CO + N2).
- Saying nitrogen is inert because it is “light”. It is inert because of the strong triple bond N≡N.
- Thinking dry chlorine bleaches. Moisture is needed: chlorine + water → HOCl → nascent oxygen, which bleaches.
- Writing O3 as an allotrope of carbon, or charcoal as crystalline. Ozone is an allotrope of oxygen; charcoal is amorphous carbon.
- Thinking all ozone is harmful. Ozone in the stratosphere protects us by absorbing UV; the CFCs are the problem.
- Balancing by changing a formula (writing H2O2 to “balance” oxygen). Only change the numbers in front.
7. Flashcards
Click a card to flip it.
8. Scored quiz
Answer all sixteen, then press Check my answers. Each wrong answer shows the page to revise. For number answers type only the number.
Your score appears below.
9. Your study checklist
Ticks come from “Mark this page as completed” at the bottom of each page.
🧭 Ready?
Next: the model test paper ▶ – attempt it on paper with a timer first, then check with the solved paper.