WHAT THE HECK!?!?!?! AM I SUPPOSE TO KNOW WHATEVER LANGUAGE THAT IS?!?!
Answer is: 4) The same subscripts are on each side of the equation.
For example, balanced chemical reaction:
2Mg + O₂ → 2MgO.
1) The same number of atoms is on each side of the equation: two magnesium atoms and two oxgen atoms.
2) The formulas for all substances are correct: in magnesium oxide (MgO), magnesium has oxidation number +2 and oxygen -2, so formula is good, because compound must be neutral.
3) The same mass is represented on each side of the equation: because there is same number of atoms, the mass is the same.
4) The same subscripts are on each side of the equation: oxygen does not have same subscripts.
Any substance that contains only one type of atom is referred to as an element.Elements are the "building blocks" of everything. Each element only contains one type of atom. If substances carry more than one type of atom, then they are compounds.
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