What is Atomic number?
The '''atomic number''' (symbol: '''Z''') of an [[atom]] is the number of [[proton]]s in the [[atomic nucleus|nucleus]] of the atom.<ref name=daintith>{{cite book|editor=Daintith, John|title=A Dictionary of Chemistry|url=https://archive.org/details/dictionarychemis00dain|publisher=Oxford University Press|page=[https://archive.org/details/dictionarychemis00dain/page/48 48]|date=2008|edition=Sixth|isbn=978-0-19-920463-2}}</ref><ref name=moore>{{cite book|first=John T.|last=Moore|title=Chemistry Essentials For Dummies|url=https://archive.org/details/chemistryessenti00moor|publisher=Wiley|date=2010|isbn=978-0-470-61836-3|page=[https://archive.org/details/chemistryessenti00moor/page/n49 36]}}</ref> The atomic number of an atom identifies which [[chemical element|element]] it is. In a [[Neutral particle|neutral]] atom, the atomic number is equal to the number of [[electron]]s orbiting the nucleus.<ref name=daintith /> The elements of the [[periodic table]] are listed in order of increasing atomic number.<ref name=moore /> Atomic number is not the same as: * '''[[atomic mass]]''' (symbol: ''m''<sub>a</sub>), which is the mass of a single atom, commonly expressed in [[atomic mass unit|unified atomic mass units]] * '''[[mass number]]''' (symbol: '''A'''), which is the sum of the number of protons and number of neutrons in the nucleus of an atom * '''[[relative atomic mass]]''' (also called '''atomic weight''';''' '''symbol: ''A''<sub>r</sub>), which is the ratio of the average mass per atom of an element from a given sample to 1/12 the mass of a carbon-12 atom. The atomic number of the periodic table directly corresponds to the number of protons which is in the atom. Once another proton is added, it is no longer the same element. The same cannot be applied to when another neutron or another electron is added. Adding more electrons will give the atom a negative charge and removing electrons will give the atom a positive charge. Metals tend to lose electrons, which creates a positive charge. Non-metals tend to gain