1.204 x 10^23 atoms of He. please consider letting me know how to do this so I can do the other questions myself

What happens to the atomic radius when an elctron is lost

For each of the following compounds, write the formula then predict whether it would be a strong, weak, or non-electrolyte when placed in di water. for the ionic compounds only, put (s) or (aq) after the forrmula formula strong, weak or non electrolyte? a calcium hydroxide b. silver carbonate c. lead(ii) sulfate d. phosphorus trifluoride e. sodium phosphide f barium sulfate g. strontium acetate h. zinc nitrate

What is the empirical formula for c4h8o2