The family member atomic massive of sodium is no 23amu (amu = atomic mass unit), the is 23 through nounits (as is suggested by words "relative").
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The relative atom mass is the ratioof the typical mass of one atom of one element(given in amu) to 1 amu. because that atoms, theatomic mass one typically uses is essentially thesum of the masses of the protons and neutronswhich consist of the nucleus of the atom; themass of each electron (~1/2000 amu) is negligiblein comparison. Protons and neutrons havesimilar masses, approximately 1 amu each. many sodium atoms have actually 11 protons and also 12 neutrons,giving a total of ~23 amu, and also dividing through 1 amuthen gives 23 for the loved one atomic mass. Notethe use of most in the preceding sentence. Thenumber of proton determines the chemical identityof an element, but the number of neutrons canvary - this are different isotope of one element.
The standard atomic weight takes intoaccount the different relative abundances and also masses that theisotopes by weighting the fixed of isotope by thefrequency of your occurrence. This is why someelements have actually fractional standard weights(e.g. Copper in ~ 63.55).
It"s because sodium atoms each have actually 11 protons,with a fixed of 1, and 12 neutrons, through a mass of1.periodic table of aspects
Number that Protons/Electrons: 11Number of power Levels: 3Number of Neutrons: 12Atomic Mass: 22.98977 amu
Most sodium atoms save twelve neutrons.That is the most common isotope that sodium. Becauseeach spirit weighs one AMU, and because each ofsodium"s eleven protons likewise weighs one AMU,twelve to add eleven is twenty-three.
It"s fairly complex nuclear physics tounderstand why some isotopes are stable and also somearen"t, but it is a basic trend the the moreprotons girlfriend have, the much more neutrons girlfriend need,and the variety of neutrons essential goes up fasterthan the variety of protons.
Relative atom mass is calculation bydividing the atom mass that an facet by whatwe contact the "unified atomic mass unit".
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The combined atomic massive unit is defined as1/12 the the mass of a carbon atom with 6 protons,6 neutrons, and also 6 electrons. The family member atomicmass of sodium is calculate by dividing theatomic fixed of sodium by the linked atomic massunit, which is 1.66*10-27 kg. Thenumber of 23 amu method that a normal, or stable,sodium atom weighs 23 linked atomic massunits. because sodium atoms have actually 11 protons,this way that a common sodium atom has actually 23 - 11 =12 neutrons. The would also have 11 electrons, butelectrons weigh so tiny compared to proton andneutrons the the electron masses can beapproximated to 0. Note that by "stable",we average that the sodium atom will not an extremely quicklychange into another element by shedding parts that itsnucleus.