Average of Investigation 1, 2, and 3
Magnesium mean = (0.04 + 0.07 + 0.07)
3
= 0.06g
Oxygen mean = (0.03 + 0.04 + 0.07)
3
= 0.047 (2 s.f.)
Magnesium Ar = 24 Oxygen Ar = 16
Conclusion
Looking at the formula for the average mass of Magnesium and Oxygen, I can see that a number of moles of magnesium will react with the same number of moles of oxygen to form magnesium oxide. This means that 1 atom of magnesium will react with 1 atom of oxygen. This means that the empirical formula of magnesium oxide is MgO.
Looking at the periodic table, I can see how Magnesium and oxygen would bond during a reaction.
Atoms bond with each other to be stable, which involves gaining a full outer shell. Magnesium is a metal, and oxygen is a non-metal (a gas), so therefore the type of bonding occurring would be ionic bonding. In this process, electrons are transferred
from the metal atom (magnesium) to the non-metal atom (oxygen). The atoms “want to” get a full outer shell, and as most atoms don’t have a full outer orbital, electrons had to be transferred.
Magnesium is in the second group of the Periodic Table, meaning that it would hold two electrons in it’s outer orbital, it’s structure pattern is 2-8-2. It “wants to” give away 2 electrons to be able to have a full outer shell and to gain the structure of a noble gas. The 2 electrons that the magnesium atom “wants to” get rid of are transferred onto the oxygen atom. Oxygen is in the sixth group of the periodic table, and therefore has 6 electrons in it’s outer shell, so needs to gain 2 electrons to achieve a full outer shell, as shown in the following diagram.
So when the two of these elements react with each other, magnesium oxide is formed. In this, there are magnesium ions, which have a positive charge x 2, and negative oxide ions, (double negative charge). This shows that for each magnesium atom there is, one oxygen atom will react with it, as only one magnesium atom is needed to react with one oxygen atom for the outer shell of each to become full; two magnesium atoms are not necessary; the diagram clearly shows for each magnesium atom, one oxygen atom will react with it. The two electrons on the outer shell of the magnesium atom are transferred over to the gap of the outer shell of the oxygen atom, leaving both atoms with a full outer shell.
Therefore, the formula for Magnesium Oxide is Mg O.
Evaluation
The scientific information in the conclusion part of this experiment supports my average of the results, which say the formula for magnesium oxide is MgO.
I decided to take the overall formula from my experiment as Mg O, rather than Mg O from the first experiment, Mg O from the second experiment, or
Mg O in the final experiment. This is because for two of the experiments, there was one more oxygen atom to react with magnesium, and for one of the experiments, there was one more magnesium atom to react with oxygen, so from this, I found the average, it being that the number of atoms was equal.
When working out the number of moles, the ratio, and the formula for each test, I worked as accurately as possible, not rounding off any decimal places right up until the very end of the calculation, to achieve the most accurate results possible and to ensure that accuracy was attained throughout the calculation. The repeat readings show that for each experiment, the number of magnesium and oxygen atoms reacting was very close, with only a difference of one atom for each test. My experiment was also accurate in the sense that when the crucible was measured, a top pan balance of an accuracy of one hundredth of a gram was used.
My final result displaying the empirical formula for Magnesium Oxide (being MgO) seems to be reliable; because scientific evidence talked about in the conclusion supports my results, saying that for each magnesium atom, one atom of oxygen will react with it to form magnesium oxide.
During the experiment, when the lid had to be lifted to allow air into the crucible (for the oxygen in the air to react with the magnesium in the crucible), some magnesium oxide that had already reacted may well have been lost when the lid was lifted. To avoid this, the crucible with the magnesium oxide inside should have been reheated and then weighed again after the final weighing, until a constant mass could be found. It would be very difficult to perform this experiment accurately for tests 1, 2, and 3.
Doing the experiment again, I would try and keep this part more accurate, but it is very difficult to maintain this level of accuracy.
To further my experiment, perhaps I would experiment with different elements, e.g. use another element in group 2 of the periodic table with oxygen, to see if the formula would involve the same number of atoms, e.g. for Beryllium Oxide, I would expect the equation to be BeO, as magnesium and beryllium have a similar atom structure. I could also react magnesium with another element in group 6, such as sulphur. For this, I would expect the formula to be Mg S, because Sulphur has a similar atomic structure to oxygen, both holding 6 electrons in their outer orbital.