Question

Aqueous solution of Ti4+ is colourless but aqueous solution of Ti3+ is violet in colour.Why?

Answer 1

because in ti+3 there is a odd electron because of this reason ti+3 is coloured

Answer 2

Answer: Because of difference in unpaired electrons.

Explanation: Titanium (Ti) is an element with atomic number of 22 and thus contains 22 electrons.

$Ti:[Ar]3d^24s^2$

Titanium on losing three electrons acquire a charge of 3+.

$Ti^{3+}:[Ar]3d^1$

Titanium on losing four electrons acquire a charge of 4+.

$Ti^{4+}:[Ar]$

Thus as $Ti^{4+}$ do not contain any unpaired electron, it is colorless. $Ti^{3+}$ is colored as it has unpaired electron which can undergo d-d transitions and when the electrons get back to their ground state , they lose energy and appears colored.