Although electrons have mass, they are not considered in determining the mass number of an atom. why?

In an investigation that uses the scientific method, which step immediately follows making a hypothesis? o summarizing the results o asking a question o making observations designing an experiment mark this and retum save and exit next submit

An atom of which element reacts with an atom of hydrogen to form a bond with the greatest degree of polarity ?

What is the compound name for the formula [ru(en)2cl2]2+ and [co(en)cl2br]-