# Atomic number

The atomic number and atomic number , atom number or proton number , symbols generally  Z , is the position of a chemical element in the periodic table of elements on. It is equal to the number of protons that are in the nucleus of each atom of this element.

In an electrically neutral atom, the atomic number is also equal to the number of electrons .

## Key figure of the elements

The atomic number is equivalent to the name of the chemical element, i.e. That is, all atoms with the same atomic number belong to the same element. The ordinal number determines the classification of the respective element in the periodic table and is usually given at the bottom left next to the element symbol .

${\ displaystyle {} _ {Z} ^ {A} {\ text {Symbol}}}$

So z. B. the carbon atom has six protons:

${\ displaystyle {} _ {\ 6} ^ {12} \ mathrm {C}}$

## Relationship with neutron and mass number

The neutron number of an atomic nucleus can be calculated with knowledge of the number of protons and the mass number . ${\ displaystyle N}$${\ displaystyle Z}$ ${\ displaystyle A}$

${\ displaystyle N = AZ}$

or resolved according to the mass number

${\ displaystyle A = N + Z.}$

## Highest atomic number

Oganesson has the highest proven ordinal number to date with 118 (as of May 2020).