What is the atom count of 3(nh4)2cl

Which statement is true about the model of the electromagnetic spectrum a: it change the frequencies of light. b: it compare wavelengths of light. c: the color of light waves can be changed using the model. d: the intensities of light waves can be decreased using the model.

Which method would be best to separate a mixture of sand and gravel

How many moles are in 1.26*10^24 particles in significant figures