For 63Cu, the atomic mass is less than 63, so this must be the dominant factor. A nucleus with greater binding energy has lower total energy, and therefore a lower mass according to Einstein’s mass-energy equivalence relation E = mc 2. The nuclear binding energy varies between nuclei.This increases the mass of nuclei with more neutrons than protons relative to the atomic mass unit scale based on 12C with equal numbers of protons and neutrons. The neutron is slightly heavier than the proton.There are two reasons for the difference between mass number and isotopic mass, known as the mass defect: For example, 63Cu (29 protons and 34 neutrons) has a mass number of 63, and an isotopic mass in its nuclear ground state is 62.91367 u. The isotopic mass usually differs for other isotopes and is usually within 0.1 u of the mass number. One unified atomic mass unit is approximately the mass of one nucleon (either a single proton or neutron) and is numerically equivalent to 1 g/mol.įor 12C, the atomic mass is exactly 12u since the atomic mass unit is defined from it. One atomic mass unit is equal to 1.66 x 10 -24 grams. The unit of measure for mass is the atomic mass unit (amu). Note that, each element may contain more isotopes, therefore this resulting atomic mass is calculated from naturally-occuring isotopes and their abundance. See also: Properties of Antimony Atomic Mass of Antimony Antimony compounds have been known since ancient times and were powdered for use as medicine and cosmetics, often known by the Arabic name, kohl.Īntimony – Properties Element Antimony Atomic Number 51 Symbol Sb Element Category Metalloids Phase at STP Solid Atomic Mass 121.76 Density at STP 6.697 Electron Configuration 4d10 5s2 5p3 Possible Oxidation States +3,5/-3 Electron Affinity 103.2 Electronegativity 2.05 1st Ionization Energy 8.64 Year of Discovery unknown Discoverer unknown Thermal properties Melting Point 631 Boiling Point 1950 Thermal Conductivity 24 Specific Heat 0.21 Heat of Fusion 19.87 Heat of Vaporization 77.14 The chemical symbol for Antimony is Sb.Īntimony is a lustrous gray metalloid, it is found in nature mainly as the sulfide mineral stibnite. Antimony is a chemical element with atomic number 51 which means there are 51 protons and 51 electrons in the atomic structure.
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