1. Nucleus always contains a neutron.   True   False   2. Atoms are electrically neutral.   True   False   3. The nucleus of an atom has almost the entire weight of the atom and it consists of protons and neutrons.   True   False   4. Neutrons are negatively-charged.   True   False   5. Hydrogen and oxygen are combined chemically in a fixed proportion of 2:1 in the compound water.   True   False   6. Atomic number of an element is the number of neutrons present in the nucleus of the atom.   True   False   7. Since an atom of the element sodium contains 11 protons and 12 neutrons, its atomic number is 23.   True   False