Ncert Solutions Chemistry Class 11th

3.58. Elements gallium and germanium were unknown at the time Mendeleev published his Periodic Table. He left the gap under aluminium and a gap under silicon, and called these elements Eka-Aluminium and Eka-Silicon. Mendeleev predicted not only the existence of gallium and germanium but also de

3.57. Ionisation enthalpy depends on the following factors:

1. Atomic size: The ionization enthalpy decreases with an increase in atomic size because with the increase in the atomic size, the number of electron shells increases. Therefore, the force that binds the electrons to the nucleus decrea

3.56. The elements of the s-block and p-block are collectively called as representative or main group elements. These include elements of group I (alkali metals), group 2 (alkaline earth metals).

3.55. The energy which is released by an atom in gaining an electron from outside the atom or ion to form a negative ion (or an anion) is called electron gain enthalpy.

The unit of electron gain enthalpy is kJ/ mol. In some cases, like in noble gases, atoms do not have any attraction to gain an

3.54. The elements of group 1 (alkali metals), group 2 (alkaline earth metals) and group 13 to 17 constitute the representative elements. They are elements of the s-block and the p-block.

1 ppm or 1 mg dm^-3.

Toxic substance that is used to kill insects are called insecticides. For example: DDT, BHC.

Carbon monoxide (CO), sulphur dioxide (SO₂) and oxides of nitrogen (NO₂).

Mixing of soil or rock particles in water is called siltation.