Chemical Bonding
NCERT Class 10 • Science • Chapter "Metals and Non metals" | NCERT Class 9 • Science • Chapter "Structure of the Atom"
Chemical Bonding
Atoms combine because a filled outermost shell is a stable arrangement. The noble gases already have it and are therefore unreactive. Every other atom gains, loses or shares electrons to reach the same arrangement, and the force that then holds atoms together is a chemical bond.
Ionic and Covalent Bonds
- The octet rule says atoms tend to achieve eight electrons in the outermost shell; hydrogen, lithium and beryllium aim for two.
- An ionic bond forms when one atom transfers electrons to another, producing oppositely charged ions held by electrostatic attraction.
- Ionic bonding usually occurs between a metal and a non metal, as in sodium chloride and magnesium oxide.
- A covalent bond forms when two atoms share electrons, which usually happens between two non metals.
- Sharing one pair gives a single bond, two pairs a double bond and three pairs a triple bond.
- Hydrogen, chlorine and water have single bonds, oxygen has a double bond and nitrogen has a triple bond.
- A metallic bond holds metal atoms together through a common pool of mobile electrons.
Properties of the Compounds
- Ionic compounds are hard crystalline solids with high melting and boiling points because the electrostatic force is strong.
- They conduct electricity in molten or aqueous form, where ions are free to move, but not in the solid state.
- They are usually soluble in water and insoluble in organic solvents such as kerosene.
- Covalent compounds have low melting and boiling points because the force between molecules is weak.
- They are generally poor conductors because they contain no free ions or electrons.
- They are usually insoluble in water but soluble in organic solvents.
| Property | Ionic Compound | Covalent Compound |
|---|---|---|
| Bond formed by | Transfer of electrons | Sharing of electrons |
| Melting point | High | Low |
| Conduction | In molten or solution state | Generally none |
| Solubility | Soluble in water | Soluble in organic solvent |
Octet rule — the tendency of atoms to gain, lose or share electrons so as to have eight electrons in the outermost shell.
Exam me kaise aata hai
- A bond formed by transfer of electrons is — ionic bond
- A bond formed by sharing of electrons is — covalent bond
- Ionic compounds conduct electricity in which state — molten or aqueous
- Nitrogen molecule has which kind of bond — triple bond
UPSC/State PSC ke liye
- Ionic solids do not conduct in the solid state because the ions are locked in the lattice, not because they are absent.
- Covalent compounds have low melting points because heating has to overcome only the weak force between molecules, not the strong bond inside them.
Yahan confuse hote hain
✗ Ionic compounds conduct electricity as solids | They conduct only when molten or dissolved | ✓
✗ A covalent bond involves transfer of electrons | Covalent bonding involves sharing | ✓
✗ All compounds dissolve in water | Covalent compounds are usually insoluble in water | ✓
Ek nazar me
- Atoms bond to reach the stable noble gas arrangement.
- Ionic bond transfers electrons; covalent bond shares them.
- Ionic compounds are hard, high melting and conduct when molten or dissolved.
- Covalent compounds melt at low temperature and conduct poorly.
Ab practice karein
Atomic structure aur periodic table se har exam me questions aate hain. ExamAtlas ke mock test se abhi practice karein.