Answer:
D
Explanation:
Because the number of protons is the same as the atomic number, we know what the number of protons has to be 26. The mass number, 55, is the same as the number of protons plus neutrons. Lastly, because there is no charge on this atom, the number of electrons would have to be the same as the number of protons, which is 26.

An atom of this isotope contains 5 protons and 10-5=5 neutrons.

The answer is A. 1.67 × 10⁻²⁶ kg.
Noble gases:) they are very non-reactive
Voltage difference is the push that causes charges to flow from high to low areas.