Some carbon was reacted with 4.2 grams of hydrogen to make 16.8 grams of methane. What mass of carbon was used?

What are the first two quantum numbers for the electrons located in subshell 4d? what are the first three quantum numbers for the electrons located in subshell 2s? how many electrons can be held in a sublevel l = 3? how many electrons can be held in the energy level n = 4? how many electrons in an atom can share the quantum numbers n = 4 and l = 3?

How many grams of magnesium metal will react completely with 8.3 liters of 5.5m hcl? show all work

What does a numerical subscript following an element in a chemical formula mean?