The mass number of an atom is basically the total number of protons and neutrons.
26.7% is the percent composition by mass of sulfur in a compound named magnesium sulfate. Explanation: Molar mass of compound = 120 g/mol.
The ability to do work or cause change is
Energy
I believe in what USA was and is able to achieve, and trust the nation in many but every ways. What really made it a developed nation is the things that happened in the last 3 Centuries, some of which are;
#1 CULTURAL TOLERANCE & IMMERSION
#2 TECHNOLOGICAL INVENTIONS & ADVANCEMENT IN THE FIELD OF SCIENCE
#3 FAST FOOD CULTURE
#4 HOLLYWOOD
#5 INTEGRITY & PATRIOTISM
#6 MASS CONSUMERISM