Astrophysics (Index)About

atomic number

(Z, proton number)
(number of protons in an atomic nucleus)

An element's atomic number (or proton number, typically symbolized as Z) is the number of protons in its nucleus, a number unique to each element. This number determines how many electrons orbit within neutral atom of the element, which, in turn, is a major determinant of the element's chemical properties.

Chemistry's periodic table of the elements lays them out by atomic number in such manner that some similarities in their chemical properties correspond to their column.

Further reading:

Referenced by pages:
alpha capture
alpha process
beta decay
calcium (Ca)
carbon (C)
electron pressure
fine structure
helium (He)
hydrogen (H)
iron (Fe)
iron peak
lithium (Li)
lanthanide (Ln)
magnesium (Mg)
neon (Ne)
neutron capture
neutron drip
nickel (Ni)
nitrogen (N)
oxygen (O)
radioactive decay
silicon (Si)
silicon burning
sodium (Na)
sulfur (S)
technetium star
trans-iron element
valley of beta stability