Which block element from the following are known as transition elements?

An ion which has $18$ electrons in the outermost shell is

The element with atomic number $23$ is placed in the periodic table in:

The correct order of $E^{\circ}_{M^{2+}/M}$ values for the four successive elements $Cr$,$Mn$,$Fe$,and $Co$ is:

Pairs of elements with the same number of electrons in their respective $4f$ orbital are [Atomic number: $Eu-63, Gd-64, Dy-66, Ho-67, Tm-69, Yb-70, Lu-71, Hf-72$]. Choose the correct answer from the options given below:

If the colours of salts of transition elements are due to the presence of unpaired electrons in the transition metal ions,which of the following ions will be colourless in aqueous solution? (The atomic numbers of $Ti$ and $Fe$ are $22$ and $26$ respectively.)