1. An element is a substance made up of different kinds of atoms.   True   False   2. The nucleus consists of protons and neutrons and is negatively-charged.   True   False   3. Isotopes have same atomic weight.   True   False   4. The number of electrons in a neutral atom is equal to its atomic number.   True   False   5. Isotopes have similar chemical properties.   True   False   6. Hydrogen and oxygen are combined chemically in a fixed proportion of 2:1 in the compound water.   True   False   7. Nucleus always contains a neutron.   True   False