Definition of element
i. A substance that cannot be decomposed chemically into other substances.
Ref: AGI
ii. A substance all of whose atoms have the same atomic number.
The first definition was accepted until the discovery of radioactivity (1896), and is still useful in a qualitative sense. It is no longer strictly correct, because (1) the natural radioactive decay involves the decomposition of one element into others, (2) one element may be converted into another by bombardment with high-speed particles, and (3) an element can be separated into its isotopes. The second definition is accurate, but has the disadvantage that it has little relevance to ordinary chemical reactions or to geologic processes.
Ref: AGI
iii. In crystallography, any point, line, or plane about which crystal structure, crystal faces, or crystal symmetry, including translation, is symmetrically arrayed.
Compare with: operation
Ref: AGI
ii. A substance all of whose atoms have the same atomic number.
The first definition was accepted until the discovery of radioactivity (1896), and is still useful in a qualitative sense. It is no longer strictly correct, because (1) the natural radioactive decay involves the decomposition of one element into others, (2) one element may be converted into another by bombardment with high-speed particles, and (3) an element can be separated into its isotopes. The second definition is accurate, but has the disadvantage that it has little relevance to ordinary chemical reactions or to geologic processes.
Ref: AGI
iii. In crystallography, any point, line, or plane about which crystal structure, crystal faces, or crystal symmetry, including translation, is symmetrically arrayed.
Compare with: operation
