Carbon, nitrogen, phosphrous, sulphur, calcium, etc, are considered as essential elements. What are the criteria for considering them as essential ?

What is an essential element ?

Why is nitrogen considered an essential element ? How do plants acquire nitrogen ?

What is 'critical concentration' of essential elements?

“Colostrum is considered essential for newborn babies". Give reason.

The criteria for the essentiality of a mineral element were given by

What process would you consider essential for maintaining life?

What processes would you consider essential for maintaining life ?

Consider the following statements 1. In pteridophytes, the phloem lacks companion cells. 2. The xylem lacks vessels in majority of pteridophytes. 3. Heterosporous pteridophytes have monoecious gametophytes. 4. Water is essential for fertilization in pteridophytes. Which of these statements are correct?

A compound of carbon, hydrogen, and nitrogen contains the three elements in the respective ratio of 9 : 1 : 3.5 Calculculate the empirical formula. If the molecular weight of the compound is 108, what its molecular formula?

Consider a positively charged C_2H_3 species in which the positively charged carbon is sp - hybridized, the uncharged carbon is sp^2 -hybridized and an empty p-orbital is perpendicular to the i system. What it the best description of this cation ?