# What does the sum of the core electrons and valence electrons equals?

If the atom is neutral, the sum of the core and valence electrons is the same as the number of protons, which is the atomic number of the element. So if the sum of the core and valence electrons in a neutral atom equals $25$, that is the number of protons in the atomic nucleus, and the atomic number of the element. We can look this up on the periodic table, and find that this element is manganese.