<span>A Helium nucleus is likely to be unstable if it has no neutrons because the remaining protons will repel electromagnetically and basically cause the atom to fall apart. The neutrons could have helped in holding everything together, and not make the protons repel.</span>
You must use the Periodic Table. Metals, on the right side, will be positive. Non-metals, left, are negative. You need to know the specific ionic charge elements.