in a triple beam balance how do you know when you have to move a weight back to the previous notches or grooves

Why do sodium and neon have vastly different chemical and physical properties despite having similar atomic masses?

1. combine iron and copper (ii) sulfate solution. (hint: iron will form the iron (iii) ion) fe + cuso4 → 2. combine lead (ii) nitrate and potassium iodide solutions. pb(no3)2+ kl → 3. combine magnesium metal and hydrochloric acid solution. mg + hcl → 4. electrolysis (splitting) of water. h2o → 5. burning magnesium. mg + o2 →

What is the number of moles of chemical units represented by 9.03x10^24? and how do i show work? (dumb it down )