In which cycle do we rely on bacteria

nitrogen cycle

Explanation:

Nitrogen enters the living world by way of bacteria and other single-celled prokaryotes, which convert atmospheric nitrogen— N 2 \text N_2 N2start text, N, end text, start subscript, 2, end subscript—into biologically usable forms in a process called nitrogen fixation.

Valence electrons are basically electrons in the outermost shell of an element.