The metal that produces red-violet colour in the non luminous flame is:
A.Ba
B.Ag
C.Rb
D.Pb

Hint: Alkali metals are basic in nature when we talk about their metal hydroxides. They react with water and form alkalis which are strong bases. Property of strong bases is to neutralise acids. They occupy the first column of the periodic table which means they come under group 1. The elements are lithium, sodium, potassium, rubidium, caesium and francium. Francium is known to be a radioactive element and has a very low half life.

Complete step-by-step answer:Hydrogen isn’t considered to be an alkali metal as it is found as gas at normal temperature and pressure. Hydrogen can show properties or transform into an alkali metal when it is exposed to extremely high pressure. They are known to be found as compounds only. The reason behind this is that they are very reactive and electropositive metals with unit valence.
When we talk about their electronic configuration it is given by\[n{s^1}\]. It is seen that they have one electron in their valence shell. For example, the electronic configuration of lithium is given by\[1n{s^1}\;2n{s^1}\].
When we talk about their important properties, we can see that their salts give out color to the flame. The reason why this occurs is that the energy of the flame leads the outermost electron to reach a state of excitation and they return to their original position due to which energy is given out which was absorbed during excitation.
\[Rb\] gives out red-violet colour to the flame. Solution is \[\left( C \right)\]

Note: As we move down the group, their nuclear charge increases and a new addition of new orbital is done. Due to this, their atomic and ionic radii of elements increase, regularly down the column. Also, every alkali metal has the largest radii than any other element in the corresponding period. When in the process of forming a cation, they tend to lose their outer shell electron and acquire a \[ + 1\] charge. They then become of the noble gas’s configuration.