The atomic mass of an element is the average mass of the atoms of an element measured in atomic mass unit (amu, also known as daltons, D). The atomic mass is a weighted average of all of the isotopes of that element, in which the mass of each isotope is multiplied by the abundance of that particular isotope. (Atomic mass is also referred to as atomic weight, but the term 'mass' is more accurate.)
You may already know that the chemical element with atomic number 35 is Bromine. But there's a lot of cool stuff about Bromine that most people don't know. Atomic number 35 - a nonmetallic heavy volatile corrosive dark brown liquid element belonging to the halogens; found in sea water Br, bromine chemical element, element - any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in combination constitute all matter. For anyone needing to memorize the symbol for 1-35 and the atomic number. Learn with flashcards, games, and more — for free. Atomic number 35: 1 n a nonmetallic heavy volatile corrosive dark brown liquid element belonging to the halogens; found in sea water Synonyms: Br, bromine Type of: chemical element, element any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in.
For instance, it can be determined experimentally that neon consists of three isotopes: neon-20 (with 10 protons and 10 neutrons in its nucleus) with a mass of 19.992 amu and an abundance of 90.48%, neon-21 (with 10 protons and 11 neutrons) with a mass of 20.994 amu and an abundance of 0.27%, and neon-22 (with 10 protons and 12 neutrons) with a mass of 21.991 amu and an abundance of 9.25%. The average atomic mass of neon is thus:
0.9048 | × | 19.992 amu | = | 18.09 amu |
0.0027 | × | 20.994 amu | = | 0.057 amu |
0.0925 | × | 21.991 amu | = | 2.03 amu |
20.18 amu |
The atomic mass is useful in chemistry when it is paired with the mole concept: the atomic mass of an element, measured in amu, is the same as the mass in grams of one mole of an element. Thus, since the atomic mass of iron is 55.847 amu, one mole of iron atoms would weigh 55.847 grams. The same concept can be extended to ionic compounds and molecules. One formula unit of sodium chloride (NaCl) would weigh 58.44 amu (22.98977 amu for Na + 35.453 amu for Cl), so a mole of sodium chloride would weigh 58.44 grams. One molecule of water (H2O) would weigh 18.02 amu (2×1.00797 amu for H + 15.9994 amu for O), and a mole of water molecules would weigh 18.02 grams.
The original periodic table of the elements published by Dimitri Mendeleev in 1869 arranged the elements that were known at the time in order of increasing atomic weight, since this was prior to the discovery of the nucleus and the interior structure of the atom. The modern periodic table is arranged in order of increasing atomic number instead.
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Element Atomic Number 35
Noun | 1. | atomic number 35 - a nonmetallic heavy volatile corrosive dark brown liquid element belonging to the halogens; found in sea water Br, bromine chemical element, element - any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in combination constitute all matter halogen - any of five related nonmetallic elements (fluorine or chlorine or bromine or iodine or astatine) that are all monovalent and readily form negative ions brine, saltwater, seawater - water containing salts; 'the water in the ocean is all saltwater' |
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