The exosphere is the thinnest layer of earths atmosphere. This also the layer of earth's atmosphere that is closest to space.
<span>Na is the chemical symbol for sodium. Na+ is formed when sodium loses an electron from its outer shell (the number of electrons and protons is now unbalanced, giving an overall positive charge) and becomes a sodium ion. Losing an electron happens when a metal reacts with a non metal.</span>
Auxin, The substance responsible for cell elongation is auxin. This phytohormone is formed in cells at the tip of the shoot and is then passed from cell to cell.
