1. Isotopes have same atomic number.   True   False   2. Isotopes have similar chemical properties.   True   False   3. Electrons are present in the nucleus.   True   False   4. Since an atom of the element sodium contains 11 protons and 12 neutrons, its atomic number is 23.   True   False   5. In a neutral atom, the number of neutrons and protons is equal.   True   False   6. Of a proton, neutron and an electron, the electron is the lightest.   True   False   7. Nucleus always contains a neutron.   True   False