Borek said:Nope. Number of protons is defined by the Pb symbol. 208 is sum of number of protons and neutrons (number of nucleons), and doesn't tell anything about how many of each there is.
It is also not uncommon to have several isotopes of different elements all having the same total number of nucleons, these are called isobars.
Borek said:It is not a chemistry question - I will move the thread to nuclear physics. 206 is definitely not enough, but perhaps there are nucleus models that allow predicting decay modes from known Z and A.
Am I misreading something here?Borek said:Nope. Number of protons is defined by the Pb symbol. 208 is sum of number of protons and neutrons (number of nucleons), and doesn't tell anything about how many of each there is.
DaveC426913 said:Am I misreading something here?
If you have a mass composed of Pb208, as the OP specified, then all the atoms contain 82 protons and 126 neutrons.
If they didn't, they would either not be the 208 isotope, or they would not be lead at all..
DaveC426913 said:Am I misreading something here?
That's what I thought you were saying, yes. Given only 208, you do not know which element it is, and thus the ratio of protons/neutrons.Borek said:Definitely there is some misunderstanding, could be my English failed.
As far as I understand the original question asked "is it possible to deduce number of protons from a single 208 number" - and then the answer is "no". At the same time when you are given entire "208Pb" information number of protons is given by the identity of the element, given by its symbol (and I believe that's what I wrote).
You have to look up the masses of possible decay products to see if the decays are possible. It is possible to estimate them theoretically but to do that precisely is way beyond the scope of homework problems. Alternatively, look up directly if the nucleus is stable.rwooduk said:One more thing if you have a free minute, for Pb 206, he said that there are no energetically favourable decay modes, can this be deduced from the 206 value? or would more information be required? or it is common knowledge and something to memorise?
No, the number of protons in an atom cannot be determined solely from the mass. Other factors, such as the number of neutrons and electrons, also contribute to the mass of an atom.
The number of protons in an atom is directly related to its mass. Each proton has a mass of approximately 1 atomic mass unit (amu), so the number of protons in an atom will contribute to the overall mass of the atom.
Yes, the mass of an atom can be used to determine the number of protons in an element. This is because each element has a unique atomic mass, which is determined by the number of protons and neutrons in the atom.
Yes, there are a few exceptions to the relationship between mass and number of protons. Isotopes, which are atoms of the same element with different numbers of neutrons, will have different masses but the same number of protons.
Knowing the number of protons in an atom is important because it determines the element that the atom belongs to. Each element has a unique number of protons, so this information helps in identifying and categorizing different elements.