Is the mass of a nucleus \nrepresents the number of \nneutrons present in the nucleus?
450990
The mass of a nucleus indicates the number of protons and neutrons present in the nucleus. An element can have more than one isotope eg Carbon 12 and Carbon 14. The former has 6 protons and 6 neutrons, The latter 6 protons and 8 neutrons. \n\nThe atomic weight of an isotope refers to the numbers of protons AND neutrons present. The atomic number of an element refers to the number of protons in all its isotopes.\n\nHydrogen, though normally just a solo proton in its nucleus, does have two isotopes, deuterium, with 1 neutron, and tritium with two neutrons.\n\nA recent question asked about silver, how many of each in its nucleus. Its atomic number is 47, so clearly 47 protons. Naturally-occurring silver is given as having  an atomic weight of 108, so answerers answered 61 neutrons.\n\nHowever there is a subtlety they missed..\n\nNaturally-occurring silver is a mixture of Ag 107 (60 neutrons) and Ag 109 (62 neutrons). (Slightly more than 50% of the former.).\n\nSo the average atomic weight of the two isotopes is 108. But there is no Ag 108 isotope present. The wrong inference was drawn.\n\nSeveral people above are confusing atomic weight and atomic number, and what they each mean. So if you don't understand several of the answers it is because they are jumbled versions of the true picture.
474775
You would expect the sum of the rest masses of the quarks to be less than the mass of the proton or neutron.  A proton/neutron is a bound state of quarks made up of quarks and gluons.  With the gluons in there, you get more mass.  It has also been shown that the mass of a nucleus is greater than the mass of its constituent protons and neutrons.  This is because the "binding energy"  that is, the energy it takes to stick the nucleus together also adds to the mass of the nucleus.  \n\nSo, the quarks+gluons+binding energy=mass of proton/neutron\nYou can't really find out a velocity from that...
107880
The atomic mass is equal (approximately) to the number of protons plus the number of neutrons.  The atomic number indicates the number of protons.  So atomic mass is atomic number plus the number of neutrons in the atom.
775515
Number of Protons/Electrons: 13 \nNumber of Neutrons: 14
982917
If there are no neutrons in the nucleus, there can be only one proton. If there were two or more protons, they would not stay together to form a nucleus without any neutrons.\n\nAnd of course an atom with only one proton in its nucleus is hydrogen.
951654
proton (positive) in the nucleus\nneutron (no charge) in the nucleus\nelectron (negative) orbits nucleus at a great distance
651393
atomic number increase by one, atomic mass stays the same.  A nutron splits into a + and a -
862578
well.. the atomic number for the nucleus is the number of protons inside of it.
798055
First the answer 129p and 130n is incorrect.  There is no element 129 and if there were it would certainly have more than 130 neutrons.  I think you are missing a piece of information, that being the atomic number or identity of the element. There are a number of elements that have an isotope that has a mass number of 259.  The 259 is the number of neutrons plus protons.  If you know the identity of the element, then you know number of protons (atomic number) and you can calculate the number of neutrons.  For example, if the isotope is No-259 then Nobelium has 102 protons and isotope would have 259-102 = 157 neutrons.  The number of electrons in an atom is equal to the number of protons.
292932
As others have said, it's relationship between energy and mass.  However, there are a few additional points about it which are interesting.  The mass here is the rest mass, the mass of an object when it is at rest relative to the person doing the measurement.  Some things, like photons, have no rest mass.  Their energy is give by E=(h-bar)(nu) where h-bar is Planck's constant divided by two pi, and nu is the frequency, in rad/sec, not Hertz. Additionally, E=MC^2 isn't the total energy for a particle, it can also have kinetic energy if it is moving with respect to the observer.  So, it's really E=MC^2+KE, where KE is the kinetic energy of the particle.    \n\nYou can also switch it around and consider that the mass, M is equal to the total energy divided by the speed of light squared.  In this case, you can calculate the mass for things which can vary based on the energy the object has, and not just the rest mass energy equivalence, but also the kinetic energy.  This is where much of the mass consumed in a nuclear reaction comes from.  Reorganization of nulcei to lower energy states gives them a lower mass, since the total energy is lower, and this change in mass is released as energetic radiation.  So, the core of a nuclear bomb contains ~ 10 kilos of highly enriched uranium, but only a tiny fraction of that is consumed in the explosion.  If all ten kilos were fully converted to energy, it would be enough energy to destroy the earth.  Instead, a tiny fraction of a gram is consumed when the nuclei undergo an out of control chain reaction, reogranizing and spitting out radiation, which destabilizes and causes the reorganization of neighboring nuclei, and so the reaction proceeds until most of the nuclei in the bomb core (called the "pit") have reorganized.  By this time, it's exploded and it would be very difficult to reassemble and weigh all the atoms left over from the reaction, but, if you could, you'd find the total would be less mass than the 10 kilos you started with.  \n\nChanges in mass when energy is absorbed or emitted is actually true for things other than nuclear reactions.  If you're running past me at 5 kilometers per hour, you actually weigh more than if you're standing stationary next to me.  However, given that the conversion ratio between mass and energy is the speed of light squared, which is a very large number, the amount of mass you gain by running at such a low speed is so small as to be unmeasurable.  Only if very large amounts of kinetic energy are involved does it become important.  If you were to fly past me at nine tenths the speed of light in a spaceship, and I could measure your mass as you passed, by, say, deflecting your path by bouncing something off you to see how much acceleration you gain for a given amount of force and using F=MA to calculate your mass, I'd find that you had a significantly higher mass.    \n\nSo, the simplest form of the statement, the one which calculates just the rest mass/energy relationship, is only part of the importance of this equation.
609337
The atomic mass of a chemical element is the mass of an atom at rest, most often expressed in unified atomic mass units. The atomic mass is often synonymous with relative atomic mass, average atomic mass and atomic weight; however, it is subtly different in that it can either be the abundance-weighted average of isotope masses of an element or the mass of a single isotope.\n\nThe relative atomic mass (also known as atomic weight and average atomic mass) is the average of the atomic masses of all the chemical element's isotopes as found in a particular environment, weighted by isotopic abundance. Periodic tables usually list these with reference to the local environment of Earth's crust and atmosphere. An uncertainty in parenthesis is often included. For artificial elements the nucleon count of the most stable isotope is listed in brackets as the atomic mass
210049
None of these particles. The mass of the proton and neutron are approximately 1 AMU, and the mass of an electron is approximately 1/1840 of that. So the electron mass is approximately 0.00054 AMU, not 0.000006 AMU .
832813
atomic mass is, well the mass. also the number of protons + neutrons. Atomic number is the number of protons, which is also the number of electrons
288934
Yes it does. In fission, the bigger nuclei breaks into smaller nuclei. If you add up the masses of the smaller nucleii, you will find it short of the bigger nuclei. This is called mass defect. This mass is converted to energy by the relation E=mc^2 . In fusin, two smaller nucleii fuse to form a bigger nuclei, which has less mass than the masses of the two smaller nucleii added. This mass defect is converted to energy here by the equation e=mc^2.
867714
Indeed, it looks as if everyone is correct. You do round to the nearest whole number. \n\nThis gives you the most commonly occurring isotope for that element. In this case O-16, which gives you the total number of neutrons + protons. To get Neutrons subtract the Atomic No. from the AMU.\n\nOxygen has other isotopes (same element with different numbers of neutrons), thus different weights. Ex: O-15, O-14, O-17, etc.\n\nGet an "A".
677530
.The neutrons and protons are arranged in a nucleus by stong nuclear forces that are revealed in fission reactions..
247154
Three reasons.\n\nProtons and neutrons do not weight exactly one atomic mass unit.  A proton has a mass of 1.007276 amu and a neutron 1.008665.\n\nNot all atoms of the same elment have the same number of neutrons.  Most carbon atoms have 6 neutrons, but a few have 7, and a very few have 8.  Atomic weight is an weighted average of naturally occuring isotopes.\n\nWhen bound together, neutrons and protons have a lower potential energy that when free.  By Einsteins formula, E=mc^2, this means atoms have a slightly lower mass than the sum of their particles.