what a number!)Įlectron - almost one two thousandth of a proton or neutron (in other words, really small!) If I got anything wrong, feel free to comment below (I would appreciate it)!Ītomic mass unit (or "amu") - also known as "u", or "unified atomic mass unit". Hi! Here are some brief notes that I took in the video. Also, scientists needed a pure isotope to base the system on. Scientists used carbon-12 because no other atom has exact whole-number masses in the amu scale. This is why the mass of carbon-12 is 12 amu, not 12.09. Some of the mass of the atom gets converted into binding energy, so the mass of the entire nucleus would actually be less than the mass of each individual proton and neutron added together. Because of energy-mass equivalence (E = mc^2), we know that energy and mass are interchangeable. Binding energy is the energy that holds the nucleus together. Since the nucleus is full of protons, which has positive charge, they would repel and the nucleus would fly apart. The missing mass is called mass defect, and it represents the binding energy. Following this logic, the carbon-12 atom's atomic mass should actually be 12.09 amu however, the mass is exactly 12 amu. So the mass of a proton is around 1.008 amu, not 1. The relative abundance of Deutrium (1 proton, 1 neutron) is so small that it is barely accounted for when calculating the average atomic mass. Protium is by far the must abundant isotope of hydrogen, and it only contains 1 proton, and no neutrons. The average atomic mass for hydrogen is actually around 1.008 amu. But after isotopes were discovered (oxygen-17, oxygen-18, etc), everything got really confusing, so scientists agreed to use carbon-12. You can also use our molar mass calculator.Good question that requires a kind of long explanation!Ī long time ago, the standard for measuring average atomic mass was actually based on oxygen, and scientists thought all oxygen was oxygen-16 (8 protons, 8 neutrons). Basically, you should know how to find the molar masses of any chemical compound now. Of nitrogen) + (six atoms x 16 grams/mole of oxygen) = 189 grams/mole ofįor all other compounds, the general idea is the same. Will be equal to (1 atom x 65 grams/mole of zinc) + (two atoms x 14 grams/mole The brackets multiplied by the subscript two). Multiplied by the subscript two) and six atoms of oxygen (three atoms in Have one atom of zinc, two atoms of nitrogen (one atom inside the brackets (1 atom x 56 grams/mole Fe) + (2 atoms x 35.5 grams/mole of chlorine) = 127 grams/mole of iron (II) chloride For example, in iron (II) chloride, or FeCl 2, you have one atom of iron and two atoms of chlorine. If you have a subscript in a chemical formula, then you multiply the number of atoms of anything next to that subscript by the number of the subscript.įor most compounds, this is easy. (1 atom x 23 grams/mole Na) + (1 atom x 35.5 grams/mole Cl) = 58.5 grams/mole NaClĢ. If we write this as a calculation, it looks like this: If we have a chemical compound like NaCl, the molar mass will be equal to the molar mass of one atom of sodium plus the molar mass of one atom of chlorine. Molar masses of chemical compounds are equal to the sums of the molar masses of all the atoms in one molecule of that compound. To do this, we need to remember a few rules.ġ. How can I find the molar mass of a chemical compound?įor any chemical compound that's not an element, we need to find the molar mass from the chemical formula. Still, aside from the exceptions above, all elements have the same molar mass as the atomic masses on the periodic table. phosphorus is normally found in clumps of four atoms, P 4, and sulfur is found in clumps of eight atoms, or S 8. That each molecule of the element has two atoms of that element stuck together.Īs a result, the formula of hydrogen is H 2, nitrogen is N 2, etc. In the case of hydrogen, nitrogen, oxygen,įluorine, chlorine, bromine, and iodine, the element is diatomic, meaning In some cases, the element is usually found in a differentįorm than just one unbonded atom. So, in our example, carbon has a molar mass of 12.01 grams per mole. For example, if you want to find the molar mass of carbon, you would find the atomic mass of carbon on the periodic table, and this is equal to the molar mass in grams per mole. The molar mass of elements is found by looking at the atomic mass of the element on the periodic table. How can I find the molar mass of an element? It is also sometimes called: Molecular Mass, Molecular Weight, Formula Mass, or Formula Weight. One atomic mass unit (u) is equal to 1/12 the mass of one atom of carbon-12. Molar mass is the mass (in atomic mass units) of one mole of a of a substance.
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