Hello there!

Greetings!

Alkali metals are group 1 metals and they have only 1 electron in the outermost shell, so they have high ionisation enthalpy and have the largest radius in their respective periods and because of all these factors, alkali metals have very high tendency of  forming a compound  by losing an electron so that they can attain the stable electronic configuration of noble gases , and thus, they are not found in free state.

Thankyou

Dear Himanshu, alkali metals are not found in free state because they have just 1 electron in their valence shell so they are ready to loose this one electron in order to achieve stable Noble gas configuration. Also, they have the largest atomic radii and highest ionisation enthalpies which favours the loss of electron.

All the best

Hope this helps