About 25 of the 92 natural elements are known to be essential to life,
but four of these-carbon (C), oxygen (O), hydrogen (H), and nitrogen (N)-make up
90% of living matter. Phosphorus (P), sulfur (S), calcium (Ca), potassium (K) and
a few other elements account for most of the remaining 4% of an organism’s weight.
Trace elements are those required by organisms in minute quantities. However,
because they are mandatory for good health, trace elements are not nutrient of
marginal importance to the organisms.