Covalent Compounds: Hydrogen Chloride, Hydrogen Fluoride and Water സഹസംയോജക സംയുക്തങ്ങൾ
Sharing is not only for two identical atoms. When hydrogen meets chlorine, fluorine or oxygen, they share electron pairs too – and the result is a compound. On this page you read Fig 3.10 and 3.11, draw hydrogen fluoride yourself, build water one bond at a time, and then compare the properties of covalent compounds (wax, kerosene, sugar, water) with those of ionic compounds like common salt.
- A covalent bond സഹസംയോജകബന്ധനം is formed by sharing electron pairs; each shared pair counts for both atoms (page 6).
- One shared pair = single bond (–), two pairs = double bond (=), three pairs = triple bond (≡).
- Hydrogen is stable with 2 electrons (the duplet of helium); most other atoms want 8 (octet).
- The properties of ionic compounds അയോണിക സംയുക്തങ്ങൾ (page 5) – you will compare them with covalent compounds in section 6.
1. Hydrogen chloride (Fig 3.10)
H₂, N₂, O₂, F₂ എന്നീ മൂലക തന്മാത്രകളിലെ സഹസംയോജകബന്ധനം മനസ്സിലാക്കിയല്ലോ. ചില സംയുക്ത തന്മാത്രകളിലെ രാസബന്ധനം കൂടി നോക്കാം. You have understood the covalent bond in the element molecules H₂, N₂, O₂ and F₂. Let us now look at the bonds in some compound molecules സംയുക്തം · തന്മാത്ര.
ഹൈഡ്രജൻ ക്ലോറൈഡ് തന്മാത്രയിലെ (ചിത്രം 3.10) രാസബന്ധനം ചിത്രീകരിച്ചിരിക്കുന്നത് ശ്രദ്ധിക്കുക. Look at how the bond in the hydrogen chloride molecule is drawn (Fig 3.10). Hydrogen (1) has 1 electron; chlorine (2, 8, 7) has 7 outer electrons.
Fig 3.10 (redrawn). Inside the H circle: 2 electrons (duplet ✓). Inside the Cl circle: 6 + 2 = 8 (octet ✓).
ഇവിടെ ഹൈഡ്രജനും ക്ലോറിനും ഇടയിൽ ഒരു ജോഡി ഇലക്ട്രോണുകൾ പങ്കുവച്ചിരിക്കുന്നതായി മനസ്സിലാക്കാം. അതുകൊണ്ട് ഹൈഡ്രജൻ ക്ലോറൈഡിൽ ഏകബന്ധനമാണുള്ളത്. Here one pair of electrons is shared between hydrogen and chlorine. So hydrogen chloride has a single bond ഏകബന്ധനം.
Q (page 54). ഹൈഡ്രജൻ ക്ലോറൈഡ് തന്മാത്രയിലെ സഹസംയോജകബന്ധനം പ്രതീകങ്ങൾ ഉപയോഗിച്ച് സൂചിപ്പിക്കൂ. Show the covalent bond in the hydrogen chloride molecule using symbols.
2. Your turn: hydrogen fluoride
Q (page 54). ചിത്രം 3.10-ൽ നൽകിയിരിക്കുന്ന മാതൃകയിൽ ഹൈഡ്രജൻ ഫ്ലൂറൈഡിലെ രാസബന്ധനം ചിത്രീകരിക്കൂ. Draw the bond in hydrogen fluoride in the same way as Fig 3.10. Fluorine is 2, 7 – just like chlorine it has 7 outer electrons. Try the drawing board below before you look at the answer.
The board starts with a wrong drawing on purpose. Change the numbers until every atom is happy: 2 round each H, 8 round the other atom – and use exactly the electrons each atom really has.
3. The water molecule (Fig 3.11)
ജലതന്മാത്രയിലെ രാസബന്ധനം ചിത്രീകരിച്ചിരിക്കുന്നത് (ചിത്രം 3.11) നോക്കൂ. Look at the picture of the bonds in the water molecule (Fig 3.11). Oxygen (2, 6) needs 2 more electrons; each hydrogen needs 1.
Fig 3.11 (redrawn) – H· + ·O· + ·H → H(··)O(··)H.
Q (page 55). ഇവിടെ എത്ര സഹസംയോജകബന്ധനങ്ങളാണ് രൂപപ്പെട്ടിരിക്കുന്നത്? How many covalent bonds are formed here?
4. Covalent compounds
Compounds formed by covalent bonds are called covalent compounds സഹസംയോജക സംയുക്തങ്ങൾ. When non-metal elements അലോഹ മൂലകങ്ങൾ combine with each other, a covalent compound is usually formed.
Water (H₂O) from the well, sugar (C₁₂H₂₂O₁₁) in your tea, carbon dioxide (CO₂) in soda, methane (CH₄) in a biogas plant, kerosene മണ്ണെണ്ണ in the lamp, the wax of a candle, coconut oil, the camphor (കർപ്പൂരം) lit at the temple – all are made of non-metal atoms (C, H, O) joined by shared pairs. Compare with common salt from the salt pans: sodium (a metal) and chlorine – an ionic compound.
5. Covalent overlap builder – compounds
Bring the hydrogen atoms in and watch each one form a shared pair with the central atom. Use "count around" to check 2 for every H and 8 for the other atom. NH₃ (ammonia) and CH₄ (methane) are extra examples for you to explore.
Like the textbook, the diagrams are drawn flat. Real H₂O, NH₃ and CH₄ molecules are not flat – their shapes come up on page 8.
6. Properties of covalent compounds
സഹസംയോജക സംയുക്തങ്ങളുടെ പൊതുസവിശേഷതകൾ – the general properties of covalent compounds (textbook page 55):
- സഹസംയോജക സംയുക്തങ്ങൾ ഖരം, ദ്രാവകം, വാതകം എന്നീ മൂന്ന് അവസ്ഥകളിലും കാണപ്പെടുന്നു.
Covalent compounds are found in all three states – solid, liquid and gas (sugar and wax · water and kerosene · carbon dioxide and methane). - ഇവ പൊതുവേ ജലത്തിൽ ലയിക്കുന്നില്ല.
They are generally insoluble in water – coconut oil and kerosene float on water and do not mix. (A few, like sugar, do dissolve; page 8 explains why.) - മണ്ണെണ്ണ, കാർബൺടെട്രാക്ലോറൈഡ്, ബെൻസീൻ മുതലായ ഓർഗാനിക് ലായകങ്ങളിൽ ഇവ ലയിക്കാറുണ്ട്.
They dissolve in organic solvents ഓർഗാനിക് ലായകങ്ങൾ such as kerosene, carbon tetrachloride and benzene – that is why kerosene removes a grease stain that water cannot. - ഇവയുടെ ഉരുകൽനിലയും (Melting point) തിളനിലയും (Boiling point) പൊതുവേ കുറവാണ്.
Their melting point ഉരുകൽനില and boiling point തിളനില are generally low – candle wax melts in the flame, ice melts at 0 °C, while common salt melts only at about 801 °C. - സാധാരണയായി ഇവ വൈദ്യുത ചാലകങ്ങളല്ല.
They are usually not electrical conductors വൈദ്യുത ചാലകം – they have no ions that can move. Sugar solution does not conduct; salt solution does (page 12 has the conductivity lab).
Kerosene catches fire easily – keep it away from flames. Carbon tetrachloride and benzene are poisonous; they are named in the book as examples only. Never try to dissolve things in them at home.
Sort the cards: ionic or covalent?
Ionic compounds vs covalent compounds
| Feature | Ionic compounds അയോണിക സംയുക്തങ്ങൾ | Covalent compounds സഹസംയോജക സംയുക്തങ്ങൾ |
|---|---|---|
| How the bond forms | transfer of electrons → oppositely charged ions held by electrostatic attraction | sharing of electron pairs between atoms |
| Elements that combine | usually a metal + a non-metal (Na + Cl) | usually non-metals (H + Cl, C + O) |
| Particles | ions – cations കാറ്റയോൺ and anions ആനയോൺ | molecules തന്മാത്ര |
| Physical state | solids; found as crystals ക്രിസ്റ്റലുകൾ | solid, liquid or gas |
| Volatility, hardness | non-volatile and hard ബാഷ്പീകരണസ്വഭാവം · കാഠിന്യം | many are soft or easily vaporised (camphor, kerosene) – go further |
| Melting and boiling points | very high | generally low |
| Solubility | generally soluble in polar solvents പോളാർ ലായകങ്ങൾ like water | generally insoluble in water; soluble in organic solvents (kerosene, carbon tetrachloride, benzene) |
| Electrical conductivity | do not conduct as solids; conduct when molten or dissolved in water | generally do not conduct |
| Electronegativity difference (page 8) | 1.7 or more | less than 1.7 |
| Examples | NaCl, MgO, CaF₂, KCl | H₂O, HCl, CH₄, CO₂, sugar |
- 📄 Covalent bond Wikipedia
Sharing electron pairs: single, double and triple bonds. - 📄 Lewis structure Wikipedia
How to draw electron dot diagrams of molecules. - 📄 Gilbert N. Lewis Wikipedia
The chemist who introduced electron dot diagrams and the shared electron pair. - 🧪 Build a Molecule (PhET simulation) PhET, University of Colorado Boulder
Join atoms to build H₂, O₂, H₂O, CO₂, NH₃ and more.
7. Check yourself
- HCl and HF: hydrogen and the halogen share one pair → single bond, H–Cl, H–F. The halogen keeps 3 lone pairs (8 in all); H has 2.
- Water: oxygen shares one pair with each hydrogen → 2 single bonds, H–O–H. Oxygen keeps 2 lone pairs.
- Compounds formed by covalent bonds are covalent compounds; non-metals combining usually give covalent compounds.
- Covalent compounds: solid, liquid or gas; generally insoluble in water but soluble in organic solvents; generally low melting and boiling points; generally do not conduct electricity.