How many electrons would weigh 1 kg?

Two persons could fit new windows in a house in 3 days. How many persons would be needed to fit the windows in one days?

How many valence electrons do the elements of group 17 containn?

How many electron must be remove from a piece of metal to give it a +ve charge of 1xx10^7C .

How many moles of electron will be required for the reduction of 1 mole of Cr_2O_7^(2-) ions to Cr^(3+)

How many ergs make one joule?

Atomic number of Mg is 12 and its mass number is 24. How many protons and electrons does a Mg^2+ ion have?