The family member atomic fixed of sodium is no 23amu (amu = atomic mass unit), the is 23 through nounits (as is argued by the word "relative").
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The relative atom mass is the ratioof the average mass of one atom of an element(given in amu) to 1 amu. because that atoms, theatomic fixed one typically uses is basically thesum that the masses of the protons and neutronswhich make up the cell core of the atom; themass of each electron (~1/2000 amu) is negligiblein comparison. Protons and neutrons havesimilar masses, approximately 1 amu each. most sodium atoms have 11 protons and also 12 neutrons,giving a full of ~23 amu, and dividing through 1 amuthen offers 23 because that the loved one atomic mass. Notethe usage of many in the coming before sentence. Thenumber of proton determines the chemical identityof one element, yet the number of neutrons canvary - these are different isotope of one element.
The standard atomic weight take away intoaccount the various relative abundances and masses the theisotopes through weighting the massive of isotopes by thefrequency of their occurrence. This is why someelements have fractional conventional weights(e.g. Copper at 63.55).
It"s due to the fact that sodium atom each have actually 11 protons,with a massive of 1, and 12 neutrons, through a mass of1.routine table of facets
Number that Protons/Electrons: 11Number of energy Levels: 3Number of Neutrons: 12Atomic Mass: 22.98977 amu
Most sodium atoms save on computer twelve neutrons.That is the most common isotope the sodium. Becauseeach neutron weighs one AMU, and also because every ofsodium"s eleven protons additionally weighs one AMU,twelve add to eleven is twenty-three.
It"s fairly complex nuclear physics tounderstand why part isotopes room stable and also somearen"t, but it is a general trend that the moreprotons friend have, the more neutrons you need,and the number of neutrons essential goes increase fasterthan the number of protons.
Relative atomic mass is calculate bydividing the atom mass of an element by whatwe speak to the "unified atom mass unit".
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The merged atomic fixed unit is characterized as1/12 that the massive of a carbon atom through 6 protons,6 neutrons, and 6 electrons. The relative atomicmass of sodium is calculate by splitting theatomic fixed of sodium by the linked atomic massunit, which is 1.66*10-27 kg. Thenumber that 23 amu method that a normal, or stable,sodium atom weighs 23 unified atomic massunits. because sodium atoms have actually 11 protons,this means that a common sodium atom has actually 23 - 11 =12 neutrons. It would likewise have 11 electrons, butelectrons sweet so little compared to proton andneutrons the the electron masses deserve to beapproximated come 0. Keep in mind that through "stable",we mean that the salt atom will not very quicklychange into an additional element by shedding parts that itsnucleus.