The diameter of a chlorine atom is 200. pm. how many chlorine atoms are required to line up end to end to stretch a distance of 1.0 mm? use 'e' for scientific notation.

The number of chlorine atoms needed would simply be the ratio of distance and diameter. But first convert 200 pm to mm:

200 pm = 2 E-7 mm             

So the number of chlorine atoms needed is:

1.0 mm / (2 E-7 mm) = 5,000,000 Chlorine atoms = 5 E6 atoms

these nuts

if you mean hydrogen and oxygen then water is the product