Chemistry · Chemical Bonding · NEET
| Electrons | Transferred (given/taken) | Shared between atoms |
| Atoms involved | Metal + non-metal | Non-metal + non-metal |
| Particles formed | Charged ions (Na+, Cl-) | Neutral molecules (Cl2) |
| Example | NaCl, MgO, CaF2 | Cl2, H2O, CH4 |
| Melting point | High (strong lattice) | Usually low (simple molecules) |
| Electrical conduction | Yes, when molten/dissolved | Mostly no (graphite is exception) |
| Electronegativity difference | Large (about 1.7+) | Small or zero |
Look at the two atoms. If it is a metal joined to a non-metal (like Na and Cl), electrons are transferred, so the bond is ionic. If it is two non-metals joined (like C and O, or H and Cl), electrons are shared, so the bond is covalent. A quick shortcut for NEET: large electronegativity difference (about 1.7 or more) means mostly ionic; small difference means covalent.
NaCl is ionic. Sodium (Na) is a metal that easily loses one electron to become Na+, and chlorine (Cl) is a non-metal that gains that electron to become Cl-. The two opposite charges attract each other. This is important for NEET because ionic solids like NaCl have high melting points and conduct electricity when melted or dissolved in water.
Metals have low ionisation energy, so they lose electrons easily and form positive ions. Non-metals have high electron affinity, so they grab electrons and form negative ions. When a metal meets a non-metal, transfer happens, giving an ionic bond. But two non-metals both want electrons, so neither gives up fully; they share instead, giving a covalent bond.
There is no single answer, and NEET can trap you here. Within a single molecule a covalent bond can be very strong. But an ionic compound is a giant 3D lattice held by strong electrostatic forces (lattice enthalpy), so ionic solids usually have much higher melting and boiling points than simple covalent molecules. Compare the whole lattice, not one bond, when a question asks about melting point.
Yes. Real bonds are rarely 100 percent one type. A bond has partial ionic and partial covalent character depending on the electronegativity difference. For example, HCl is covalent but polar (partly ionic). NEET often tests this idea of 'percentage ionic character' and Fajans' rules, which describe covalent character inside ionic compounds.
Choose the correct statement:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Ionic bonds transfer electrons from one atom to another to make charged ions that attract. Covalent bonds share electrons between two atoms. Transfer versus sharing is the core difference.
Ionic: NaCl (sodium chloride) and MgO (magnesium oxide). Covalent: Cl2 (chlorine gas) and H2O (water). Ionic pairs a metal with a non-metal; covalent joins non-metals.
Ionic solids are giant lattices held by strong electrostatic attraction between many positive and negative ions (high lattice enthalpy). Breaking the whole lattice needs a lot of energy, so melting points are high.
Ionic compounds conduct when molten or dissolved in water because the ions become free to move. Most simple covalent compounds do not conduct, since they have no free ions. (Graphite is a special covalent exception due to delocalised electrons.)
It predicts bond type. A large difference (roughly 1.7 or more) means the bond is mostly ionic; a small difference means covalent; zero difference (same atom) means pure non-polar covalent.
