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 Boron Atomic Mass of Boron ![]() Most of (n,alpha) reactions of thermal neutrons are 10B(n,alpha)7Li reactions accompanied by 0.48 MeV gamma emission.īoron – Properties Element Boron Atomic Number 5 Symbol B Element Category Metalloids Phase at STP Solid Atomic Mass 10.811 Density at STP 2.46 Electron Configuration 2s2 2p1 Possible Oxidation States +3 Electron Affinity 26.7 Electronegativity 2.04 1st Ionization Energy 8.298 Year of Discovery 1808 Discoverer Davy, Sir Humphry & Thénard, Louis-Jaques & Gay-Lussac, Louis-Joseph Thermal properties Melting Point 2079 Boiling Point 2550 Thermal Conductivity 27 Specific Heat 1.02 Heat of Fusion 50.2 Heat of Vaporization 489.7 Isotope 11B has absorption cross-section for thermal neutrons about 0.005 barns (for 0.025 eV neutron). Its (n,alpha) reaction cross-section for thermal neutrons is about 3840 barns (for 0.025 eV neutron). In nuclear industry boron is commonly used as a neutron absorber due to the high neutron cross-section of isotope 10B. ![]() Natural boron consists primarily of two stable isotopes, 11B (80.1%) and 10B (19.9%). There are over 100 different borate minerals, but the most common are: borax, kernite, ulexite etc. Significant concentrations of boron occur on the Earth in compounds known as the borate minerals. Boron is a chemical element with atomic number 5 which means there are 5 protons and 5 electrons in the atomic structure.
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