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Chemistry Review


Table 1
The Most Common Elements on Earth and Their Distribution in the Human Body
Element
Symbol
Atomic Number
% of Human Body by Weight

Approximate % of Earth's Crust by Weight

Importance of Function
Oxygen
O
8
65.0
46.6
Necessary for cellular respiration, component of water
Carbon
C
6
18.5
0.03
Backbone of organic molecules
Hydrogen
H
1
9.5
0.14
Electron carrier, component of water and most organic molecules
Nitrogen
N
7
3.3
Trace
Component of all proteins and nucleic acids
Calcium
Ca
20
1.5
3.6
Component of bones and teeth, trigger for muscle contraction
Phosphorus
P
15
1.0
0.07
Backbone of nucleic acids, important in engergy transfer
Potassium
K
19
0.4
2.6
Principal positive ion in cells, important nerve function
Sulfur
S
16
0.3
0.03
Component of most proteins
Chlorine
Cl
17
0.2
0.01
Principal negative ion bathing cells
Sodium
Na
11
0.2
2.8
Principal positive ion bathing cells, important in nerve function
Magnesium
Mg
12
0.1
2.1
Critical component of many energy-transferring enzymes
Iron
Fe
26
Trace
5.0
Criticial component of hemoglobin in the blood
Copper
Cu
29
Trace
0.01
Key component of many enzymes
Zinc
Zn
30
Trace
Trace
Key component of some enzymes
Molybdenum
Mo
42
Trace
Trace
Key component of many enzymes
Iodine
I
53
Trace
Trace
Component of thyroid hormone
Silicon
Si
14
Trace
27.7
N/A
Aluminum
Al
13
Trace
6.5
N/A
Manganese
Mn
25
Trace
0.1
N/A
Fluorine
F
9
Trace
0.07
N/A
Vanadium
V
23
Trace
0.01
N/A
Chromium
Cr
24
Trace
0.01
N/A
Boron
B
5
Trace
Trace
N/A
Cobalt
Co
27
Trace
Trace
N/A
Selenium
Se
34
Trace
Trace
N/A
Tin
Sn
50
Trace
Trace
N/A