Chemistry · Chemical Bonding · NEET
In an ionic solid, positive and negative ions are held by strong electrostatic (coulombic) force in every direction, forming a giant lattice. To melt or boil it, you must break a very large number of these strong ion-ion attractions. That needs a lot of heat, so the melting and boiling points are high. Stronger attraction (smaller, higher-charge ions) means higher lattice enthalpy and higher melting point. This is why NaCl melts at about 801 degrees C.
Electric current needs charged particles that can MOVE. In a solid ionic crystal the ions are locked tightly in fixed positions in the lattice, so they cannot move and cannot carry current. When you melt the solid or dissolve it in water, the lattice breaks and the ions become free to move. These free ions then carry the current. So: solid = no conduction, molten or aqueous = conducts.
They are both hard and brittle. Hard means they resist scratching, because the strong ion attractions hold the lattice firmly. Brittle means they crack easily when you hit them. When a layer of the crystal is pushed, like-charged ions (for example + next to +) come to face each other, they repel, and the crystal splits along that plane. So a small blow can shatter an ionic crystal even though it is hard.
Water is a polar solvent. Its partially negative oxygen pulls on the positive ions and its partially positive hydrogens pull on the negative ions. This pulling (hydration) supplies energy to break the lattice, so the compound dissolves. Non-polar solvents like petrol or benzene cannot pull on ions this way, so ionic compounds do not dissolve in them. Rule of thumb: ionic and polar dissolve in polar water.
There is no single small NaCl molecule. Instead each Na+ is surrounded by six Cl- and each Cl- by six Na+ in a repeating 3D lattice. NaCl is just the simplest whole-number ratio of ions, called a formula unit. So the ionic bond is non-directional (equal in all directions) and the whole crystal is one giant structure, not separate molecules.
Yes. Because ions pack in a fixed orderly repeating pattern, ionic solids are crystalline with sharp melting points and definite geometric shapes. The ionic bond itself is non-directional: the electrostatic pull acts equally in all directions, unlike a covalent bond which points along a fixed direction. This is why ionic solids form regular crystal shapes such as cubes.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The molten (liquid) state and the aqueous (dissolved in water) state. In both, the lattice is broken and ions can move freely to carry current. The solid state does not conduct.
High. Strong electrostatic force between the ions must be overcome to melt them, which needs a lot of heat. NaCl melts near 801 degrees C.
Most are, because polar water molecules pull the ions out of the lattice (hydration). They are generally insoluble in non-polar solvents like benzene or petrol.
When a layer is shifted, like charges line up and repel each other, so the crystal splits along that plane. A small force can shatter it even though it is hard.
It is the simplest whole-number ratio of ions in an ionic compound, such as NaCl. Ionic compounds do not have separate molecules; they form one giant repeating lattice.
