››More information on molar mass and molecular weight. In chemistry, the formula weight is a quantity computed by multiplying the atomic weight (in atomic mass units) of each element in a chemical formula by the number of atoms of that element present in the formula, then adding all of these products together. Yttrium (Y) is a silvery metal that has the atomic number 39 in the periodic table. It is a Transition metal and located in Group 3 of the periodic table. It has the symbol Y.
![Symbol Symbol](/uploads/1/3/4/0/134036206/508996480.png)
Noun | 1. | atomic number 39 - a silvery metallic element that is common in rare-earth minerals; used in magnesium and aluminum alloys Y, yttrium metal, metallic element - any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc. fergusonite - a dark mineral consisting of oxides of yttrium and erbium and tantalum and other minerals gadolinite, ytterbite - a mineral that is a source of rare earths; consists of silicates of iron and beryllium and cerium and yttrium and erbium xenotime - a brown-to-yellow mineral that is a phosphate of yttrium in crystalline form |
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In the modern periodic table, the elements are listed in order of increasing atomic number. The atomic number is the number of protons in the nucleus of an atom. The number of protons define the identity of an element (i.e., an element with 6 protons is a carbon atom, no matter how many neutrons may be present). The number of protons determines how many electrons surround the nucleus, and it is the arrangement of these electrons that determines most of the chemical behavior of an element.
Atomic Number 12
In a periodic table arranged in order of increasing atomic number, elements having similar chemical properties naturally line up in the same column (group). For instance, all of the elements in Group 1A are relatively soft metals, react violently with water, and form 1+ charges; all of the elements in Group 8A are unreactive, monatomic gases at room temperature, etc. In other words, there is a periodic repetition of the properties of the chemical elements with increasing mass.
Atomic Number 39 Element
In the original periodic table published by Dimitri Mendeleev in 1869, the elements were arranged according to increasing atomic mass— at that time, the nucleus had not yet been discovered, and there was no understanding at all of the interior structure of the atom, so atomic mass was the only guide to use. Once the structure of the nucleus was understood, it became clear that it was the atomic number that governed the properties of the elements.