If you know only the number of neutrons can you determine what the element is?
It is not possible to accurately identify an element given only the number of neutrons. All atoms are made of three particles: electrons, protons and neutrons. The number of electrons is equal to the number of protons if the atom is uncharged. The atomic mass of an element is the sum of the mass of all the particles. As electrons have a very small mass as compared to the other constituent particles, the mass of an atom can be taken to be the sum of the mass of protons and neutrons. The atomic number of an atom is the number of neutrons it has. This is unique and most chemical properties of an element are determined by its atomic number.
The number of neutrons in the atoms of many elements is the same. For example, boron and carbon have 6 neutrons each, fluorine and neon have 10 neutrons each, etc.
Different isotopes of an elements have the same number of protons but differ in the number of neutrons in the atom. This makes it virtually impossible to uniquely identify an element if only the number of neutrons in the atom is given.
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