Depiction of Greek philosopher Empedocles' 450BC "standard model" of physics, in which the universe consisting of four elements (earth, air, water, and fire), depicted above, and two forces (attraction and repulsion).
In chemistry, element is an atom or pure chemical substance characterized by an atomic number Z, the number of protons its nucleus, numbering from 1 to 118, of which 92 are naturally occurring elements, at earth-bound conditions. [1]

The big five elements that comprise 98 percent of the structural mass of a human are: oxygen O (61%), the central component of blood, carbon C (23%) and hydrogen H (10%), the central components of the brain, nitrogen N (2.6%), the central component of protein, and calcium Ca (1.4%), the central component of bone.

Earth
Vernadsky was one of the first to note that the elements of the periodic table do not distribute themselves uniformly, stating for instance that elements with even atomic numbers predominate in the earth’s crust. [4]

Human mass composition tables
Mass composition tables for biological entities are difficult to come by. In 1899, English physiologist John Thornton stated that there were 72 elements known in chemistry and that 14 of these enter into the composition of the human body: oxygen, carbon, hydrogen, nitrogen, sulphur, phosphorus, chlorine, sodium, potassium, calcium, magnesium, iron, fluorine, and silicon; and noted that other elements, such as manganese and lead (anti-element: poison), have sometimes been found in small quantities. [7]

In 1968, American biochemist Harold Morowitz, in his Energy Flow in Biology, is said to have given a table that compares the element contents of twenty-three elements, namely C, H, N, O, P, S, Ca, Na, K, Mg, Cl, Fe, Si, Zn, Rb, Cu, Br, Sn, Mn, I, Al, and Pb, of man, alfalfa, copepod, and bacteria. [5]

One of the best books to given element counts in humans is English chemist John Emsley's 2001 Nature's Building Blocks: an A-Z Guide to the Elements, a book which functioned as one of the principle sources in the calculation of the formula for one human molecule by American chemical engineer Libb Thims, between 2002 and 2007. [6]

The following is a 2009 depiction of the "essential" elements in the human body, according to the University of Waikato: [3]

which lists 25 elements.

Human molecule
The following table lists the 26 functional elements that comprise one human molecule, according to the 2002 calculation of American chemical engineer Libb Thims. The less-accurate 22-element and 12-element empirical human molecular formulas for one human molecule by American limnologists James Elser and Robert Sterner (2000) and New Scientist (2005), respectively, are shown below for comparison. [2]

 $H_{375,000,000} O_{132,000,000} C_{85,700,000} N_{6,430,000} Ca_{1,500,000} P_{1,020,000} S_{206,000} Na_{183,000} \,$$K_{177,000} C_{l127,000} Mg_{40,000} Si_{38,600} Fe_{2,680} Zn_{2,110} Cu_{76} I_{14} Mn_{13} F_{13} Cr_7 Se_4 Mo_3 Co_1 \,$ (Sterner and Elser, 2000) $H_{2.5E9} O_{9.7E8} C_{4.9E8} N_{4.7E7} P_{9.0E6} Ca_{8.9E6} K_{2.0E6} Na_{1.9E6} S_{1.6E6} Cl_{1.3E6} Mg_{3.0E5} \, \,$$Fe_{5.5E4} F_{5.4E4} Zn_{1.2E4} Si_{9.1E3} Cu_{1.2E3} B_{7.1E2} Cr_{98} Mn_{93} Ni_{87} Se_{65} Sn_{64} I_{60} Mo_{19} Co_{17} V \,$ (Thims, 2002) $H_{15,750} N_{310} O_{6,500} C_{2,250} Ca_{63} P_{48} K_{15} S_{15} Na_{10} Cl_{6} Mg_{3} Fe_{1} \,$ (New Scientist, 2005)

The four functional elements missing from Sterner and Elser's formula, i.e. Tin (Sn), Selenium (Se), Nickel (Ni), and Vanadium (V), as determined by Thims, are shown in bold below, listed adjacent to their known function:

 # Name Symbol CPK(jmol) %Mass Picture Z Function 1 Oxygen O 61 8 Roughly 60% of the body is H2O, which is essential for almost all chemical reactions within the body. 2 Carbon C 23 6 Is a major elemental component of carbohydrates and fats. 3 Hydrogen H 10 1 Is a major elemental component of proteins, carbohydrates, and fats. 4 Nitrogen N 2.6 7 Is a major elemental component of proteins (comprised of N, H, C, and O). 5 Calcium Ca 1.4 20 Used in the development and maintenance of bone structure and development. Functions in the clotting process, nerve transmission, muscle stimulation, parathyroid hormone function, and metabolism of vitamin D, etc. 6 Phosphorus P 1.1 15 Plays a part in almost every chemical reaction within the body because it is present in every cell. Forms calcium phosphate with calcium in the bones and teeth in a 2-1 ratio. Is important in the utilization of carbohydrates, fats, and proteins for growth, maintenance, and repair, etc. 7 Potassium K 0.3 19 Functions mainly in the intercellular fluid as the primary ion force. Potassium together with sodium helps regulate the water balance within the body. Potassium regulates the transfer of nutrients to the cell, transmits electrochemical impulses, and is necessary for normal growth enzymatic reactions, etc. 8 Sulfur S 0.2 16 Keeps hair glossy and smooth and keeps the complexion clear and youthful. Sulfur is an important elemental constituent of thiamin, biotin, methionine, cystine, and cysteine. It disinfects the blood, resists bacteria, and stimulates bile production in the liver, etc. 9 Chlorine Cl 0.18 17 Helps regulate acid alkali balance, stimulates production of hydrochloric acid, stimulates the liver to function as a filter for wastes, aids in keeping joints and tendons in youthful shape, and helps distribute hormones, etc. 10 Sodium Na 0.17 11 Is found in every cell in the body. Sodium functions with potassium to equalize the acid-alkali factor in the blood. Along with potassium, it helps regulate water balance within the body. Sodium keeps blood minerals soluble, so they will not build up as deposits in the bloodstream, etc. 11 Magnesium Mg 0.029 12 70% of the bodies magnesium supply is located in the bones together with calcium and phosphorus, while 30% is found in cellular fluids and some soft tissue. Is involved with energy production of glucose, protein and nucleic acid synthesis, the formation of urea, vascular tone, muscle impulse transmission, electrical stability of the cells, and neurotransmission, etc. 12 Iron Fe 0.012 26 The major function of iron is to combine with protein and copper in making hemoglobin. Iron builds up the quality of the blood and increases resistance to stress, the immune system, energy production, growth in children, and resistance to disease. 13 Fluorine F 0.004 9 Research indicates that fluorine increases the deposition of calcium, thereby strengthening the bones. Helps reduce the formation of acid in the mouth caused by carbohydrates, thereby reducing the likelihood of tooth decay. 14 Zinc Zn 0.003 30 Helps fight disease, protect the immune system, involved in the Krebs cycle, has been found to increase the male sex drive, is a constituent of more that 2,000 enzymes involved in digestion and metabolism, etc. 15 Silicon Si 0.001 14 Is needed for the connective tissues of the body such as the tendons, cartilage, blood vessels, nails, skin, and hair, and is essential for their integrity. Silicon works with calcium to make strong bones, proper levels are essential during growth periods, and it is helpful in the prevention of cardiovascular disease, etc. 16 Copper Cu 0.0003 29 Involved in the synthesis of hemoglobin, collagen, and the neurotransmitter noradrenalin. Is an important blood antioxidant, prevents the rancidity of polyunsaturated fatty acids, and helps cell membranes remain healthy. 17 Iodine I 0.00003 53 Aids in the development and functioning of the thyroid gland, and is an integral part of thyroxine. Iodine plays an important role in regulating cellular oxidation, promotes growth and development, and stimulates the basal metabolic rate—helping the body burn excess fat. 18 Tin Sn 0.00003 50 Deficiency results in poor growth and diminished hemoglobin synthesis. 19 Boron B 0.00003 5 A trace mineral essential for healthy bones. 20 Selenium Se 0.00002 34 Is a natural antioxidant that protects against free radicals and appears to preserve elasticity of tissue that become less elastic with aging. Is necessary for the production of prostaglandins, and pancreatic function depends upon selenium, etc. 21 Chromium Cr 0.00002 24 Stimulates the activity of enzymes involved in the metabolism of glucose for energy and the synthesis of fatty acids and cholesterol. It appears to increase the effectiveness of insulin and its ability to handle glucose, preventing hypoglycemia or diabetes. The mineral may also be involved in the synthesis of protein through its binding action with RNA molecules. 22 Manganese Mn 0.0002 25 Functions as an important antioxidant in the prevention of toxic oxygen forms. It plays a role in activating numerous enzymes that are necessary for utilization of choline, biotin, thiamine, and ascorbic acid. Is a catalyst in the synthesis of fatty acids, cholesterol, and mucopolysaccharides, etc. 23 Nickel Ni 0.0002 28 May be a factor in hormone, lipid, and membrane metabolism and cell integrity. Significant amounts are found in DNA and RNA. May be involved in glucose metabolism, etc. 24 Molybdenum Mo 0.000007 42 Is an essential part of two enzymes: xanthine oxidase—which aids in the mobilization of iron from the liver reserves and helps change iron from ferrous to ferric, and aldehyde oxidase—which is necessary for the oxidation of fats. It is also a factor in copper metabolism, nitrogen metabolism, and the final stages of urine production, ect. 25 Cobalt Co 0.000004 27 Necessary for the normal functioning and maintenance of red blood cells as well as all other body cells; and is a constituent of vitamin B12. 26 Vanadium V 0.0000002 23 Has been shown to reverse diabetes. Inhibits cholesterol synthesis. Bones, cartilage, and teeth require it for proper development. It has been shown to have a function in cellular metabolism, iron metabolism, and red blood cell growth, etc.

Quotes
The following are related quotes:

“By the term ‘elements’, we mean to express those simple and indivisible atoms of which matter is composed, it is extremely probable we know nothing at all. about them; but, if we apply the term elements or principles of bodies, to express our idea of the last point which analysis is capable of reaching, we must admit, as elements, all the substances into which we are able to reduce bodies by decomposition.”
— Antoine Lavoisier (1789), Elements of Chemistry (pg. xxiv)

“When you look at the ingredients of the universe (Ѻ), the number one ingredient is hydrogen. Next is helium. Next is oxygen. Then nitrogen. Then, when you look at earth, because we like to think of ourselves as ‘special’, the number one element in the human body (Ѻ): hydrogen [No: #3], matches the universe. Number two is oxygen [No: #1]. Matches the universe. Number three: carbon [No” #2]. Matches the universe. Number four: nitrogen [Correct]. Matches the universe. And for each of us, the fifth element – “other” [No] – is the same in both places.”
Neil Tyson (c.2014), “Dialogue on Origin of Life” (1:14-2:35) (Ѻ)
 A 2012 “human chemistry” artwork: a pie chart style human element composition overlaid on a skull, by designer Mathieu Michaux. [9]

Human element
Human chemical element
Chocolate (element) diagram
Lavoisier’s list of the elements (1789)

References
1. Daintith, John. (2005). Oxford Dictionary of Chemistry. Oxford University Press.
2. (a) Thims, Libb. (2008). The Human Molecule (issuu) (preview) (Google Books) (docstoc) (pgs. 52-55). LuLu.
(b) Sterner, Robert W. and Elser, James J. (2002). Ecological Stoichiometry: the Biology of Elements from Molecules to the Biosphere, (chapter one), (pgs. 2-3, 47, 135). Princeton: Princeton University Press.
(c) Author. (2005). “That’s Life”, New Scientist, Dec 03.
3. Essential Elements (University of Waikato) – ScienceLearn.org.nz.