Give the chemical symbol for one element with an electron configuration that ends with np^2, where n is any principal quantum number.

the electronic configuration  is the arrangement of electrons in an atom in different shells and sub-shells. after the discovery of the shells and sub-shells, various physical and chemical properties of the elements were linked to the  electronic configuration. as a result, attempts were made to arrange elements by their electronic configuration, so that their properties would obviously fall in a trend. subsequently, the modern arrangement is evolved wherein elements are organized by atomic number. this is known as the  modern periodic table.

the modern periodic table has elements arranged according to their electronic configurations. from left to right, i.e., in a period, the arrangement is such that each subsequent electron is added to the same shell.  there are certain steps for writing the electronic configuration.step-1 

find out the atomic number of the element from the periodic table. since, in an atom, the number of protons which is the atomic number is equal to the number of electrons, the atomic number will give you the information about the number of electrons in that atom. let's take the example of calcium. the atomic number of calcium is 20.step-2

now, fill electrons by following the arrows of the electron configuration chart. remember that the s-orbital can accommodate a maximum of two electrons while the p-orbital sets can hold six electrons in three orbitals. in the same way, d-orbital set contains ten and f-orbital sets contain fourteen electrons in five and seven orbitals respectively.step-3

after filling given electrons in the energy levels, write the  electronic  [x] [y]  [z]

where x represents the energy level, y is for the sub-shell which is named as  s, p, d, and f. the number of sub-shells increases with the energy level. the number z is the number of electrons present in a sub-shell.

we can represent electron configuration chart by using principle quantum number notifications also.configuration  in the given manner.