If two protons and two neutrons are removed from the
nucleus of an oxygen-16 atom, a nucleus of which element
Oxygen is element number 8 on the Periodic Table of the Elements. This means it has 8 protons in its nucleus. Oxygen-16 has 8 protons and 8 neutrons. Neutrons is an issue of weight only. It has nothing to do with the classification. After this atom has lost two protons, it is Carbon. Furthermore...
(16 amu)-[(2 protons)+(2 neutrons)=12
amu is Atomis Mass Units.
It is Carbon-12.