You would add 200+203+209 and get 612. Then divide 612 by three. (612/3) to get that the average Atomic Mass is 204.
Because the isotopes do not appear in equal amounts. This is hardly surprising since many isotopes experience radioactive decay and change to other elements after decay while stable isotopes persist - thus stable isotopes will usually dominate as the most common isotopes for individual elements with those with the longest half-lifes being more common than those with shorter half-lifes. Of course when you get into the heaviest elements there don't seem to be any stable isotopes so those with longest half life dominate.
The average atomic mass is included in the periodic table due to the varying amounts of isotopes that exist on the planet for each atom. Because isotopes of atoms have a different weight than the original, the atom can be found weighing different amounts depending on how much of the isotope is present. These ratios in isotope amounts change over time. The average atomic mass of Carbon on a table from the 1960's will not be same as the mass on a table from 2000's. Although these changes will be small, in calculations they can add up to significant differences in results.
Because copper has isotopes. All Copper atoms have exactly the same number of protons, but not all of them have the same number of neutrons. The ones with different numbers of neutrons are known as isotopes. A given sample of Copper will contain various amounts of each of its isotopes. The atomic mass (weight) is an average weight, based on the percentages of the isotopes
Average atomic mass I think.
Most elements have more than one isotope stable against radioactive decay, and these isotopes, each of which individually has an integral mass number, occur naturally in amounts that do not lead to integral average gram atomic masses.
All of the isotopes in an element's atomic masses divided by the amount of isotopes there are is the weighted-average mass of the mixture of an elements isotopes.
Because the isotopes do not appear in equal amounts. This is hardly surprising since many isotopes experience radioactive decay and change to other elements after decay while stable isotopes persist - thus stable isotopes will usually dominate as the most common isotopes for individual elements with those with the longest half-lifes being more common than those with shorter half-lifes. Of course when you get into the heaviest elements there don't seem to be any stable isotopes so those with longest half life dominate.
The average atomic mass is included in the periodic table due to the varying amounts of isotopes that exist on the planet for each atom. Because isotopes of atoms have a different weight than the original, the atom can be found weighing different amounts depending on how much of the isotope is present. These ratios in isotope amounts change over time. The average atomic mass of Carbon on a table from the 1960's will not be same as the mass on a table from 2000's. Although these changes will be small, in calculations they can add up to significant differences in results.
6.941 is the average mass of lithium's isotopes. The majority of lithium (on average about 92.5%) is lithium-7 with 3 protons and 4 neutrons while about 7.5% is lithium-6 with 3 protons and 3 neutrons. A number of other isotopes exist but only in trace amounts.
Yes, weighted by how often the isotopes are found in nature.
average atomis mass
The average of all the naturally occurring isotopes of a particular element are an element's atomic Mass.
Yes, the reason that an element's average atomic mass is often a decimal number is the fact that most elements have more than one isotope stable against radioactive decay and that these isotopes, each of which individually has an integral mass number, occur naturally in amounts that do not lead to integral average gram atomic masses.
the Atomic Mass
the average mass numbers of the isotopes of an element
Average atomic mass I think.
Because copper has isotopes. All Copper atoms have exactly the same number of protons, but not all of them have the same number of neutrons. The ones with different numbers of neutrons are known as isotopes. A given sample of Copper will contain various amounts of each of its isotopes. The atomic mass (weight) is an average weight, based on the percentages of the isotopes