ABSTRACT
Even though an atom is the smallest chemically distinct particle of an element, it does consist of smaller units, the subatomic particles. There are three types of subatomic particles found in atoms: protons, neutrons, and electrons. The number and arrangement of these particles in the atom determine which element it is and how it will react in biological or chemical processes. Each proton carries the same positive electrical charge, and the neutron is electrically neutral. These two particles have almost the same mass and are joined tightly together in the tiny central part of the atom, the nucleus. Each electron carries a negative electrical charge that exactly balances the positive charge on the proton. Electrons have a very small mass compared with protons and neutrons. They are
Element Name Symbol Role in Living Organisms Source Used by Man
Carbon C Constituent of protein, carbohydrate, fat Meat, fruit, vegetables
Hydrogen H Body uid, essential for protein, carbohydrate, fat Water
Oxygen O Essential for respiration, body uid, protein, carbohydrate, fat
Air and water
Nitrogen N Constituent of proteins, nucleic acids, chlorophyll
Meat and sh
Phosphorus P Essential for ATP, phospholipids, nucleic acids Meat and milk
Sulphur S Component of proteins, coenzyme A Meat, sh, eggs
Chlorine Cl Ion balance across membranes, stomach acid Table salt, salted foods
Sodium Na Ion balance across membranes Table salt, salted foods
Potassium K Anion-cation balance across membranes, nerve impulses
Meat, green vegetables
Calcium Ca Component of bones, teeth, invertebrate shells, plant cell walls, essential for blood clotting
Hard water, milk
distributed around the nucleus in discrete energy levels or orbitals. The three subatomic particles are compared in Table 1.3. The same three subatomic particles are present in the atoms of every element but occur in different numbers and proportions in different elements.
