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.
Your answer is (4) 4, because the alpha particle is a helium nucleus (either an ion or an ejected particle from alpha decay), and it has a mass number of 4, being consisted of four nucleons, (2 protons and 2 neutrons).
Answer:

Explanation:
Hello!
In this case, as we know the mass of the total sample, we can first compute the mass of oxygen:

Next, we compute the moles of each element:

Now, we divide the moles by 0.184 moles, the fewest ones, to obtain:

Therefore, the empirical formula is:

Regards!
Protons have a mass of 1
Neutrons have a mass of 1
So 13*1 + 14*1 = Mass number 27
The balloon will shrink in the freezer. This a good way to demonstrate that a gas's volume and/or pressure will decrease when the temperature of the gas decreases.