What is the electronic configuration of an atom for a chemical element whose formula is R2O7?

Answer: ns ^ 2 np ^ 5, where n is the number of the period in which the required element is located.
Explanation of the solution to the problem: chemical elements, the formula of the higher oxide of which R2O7 is halogens, that is, elements that are in group VII of the periodic table of elements of D.I.Mendeleev, which means that at the external level these elements have 7 electrons. Accordingly, their electronic configuration of the outer layer is as follows: ns ^ 2 np ^ 5. For example:
for F: the atom has only 9 electrons (the charge of the atom is 9), therefore – 1s ^ 2 2s ^ 2 2p ^ 5 (the power indicates the number of electrons on this sublevel, and their total number should be equal to the total number of electrons in the atom).
for Cl: 17 electrons in total – 1s ^ 2 2s ^ 2 2p ^ 6 3s ^ 2 3p ^ 5.