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A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [ 1 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...
For example, from Fe 2+ + 2 e − ⇌ Fe(s) (–0.44 V), the energy to form one neutral atom of Fe(s) from one Fe 2+ ion and two electrons is 2 × 0.44 eV = 0.88 eV, or 84 907 J/(mol e −). That value is also the standard formation energy (∆ G f °) for an Fe 2+ ion, since e − and Fe( s ) both have zero formation energy.
An element's placement on the periodic table indicates whether its chemical charge is negative or positive. Looking at the table, one can see that the positive charges are on the left side of the table and the negative charges are on the right side of the table. Charges that are positive are called cations. Charges that are negative are called ...
Each chemical element has a unique atomic number (Z— for "Zahl", German for "number") representing the number of protons in its nucleus. [4] Each distinct atomic number therefore corresponds to a class of atom: these classes are called the chemical elements. [5] The chemical elements are what the periodic table classifies and organizes.
The first molar ionization energy applies to the neutral atoms. The second, third, etc., molar ionization energy applies to the further removal of an electron from a singly, doubly, etc., charged ion. For ionization energies measured in the unit eV, see Ionization energies of the elements (data page). All data from rutherfordium onwards is ...
The first of these quantities is used in atomic physics, the second in chemistry, but both refer to the same basic property of the element. To convert from "value of ionization energy" to the corresponding "value of molar ionization energy", the conversion is: 1 eV = 96.48534 kJ/mol 1 kJ/mol = 0.0103642688 eV [12]
In 1869, Dmitri Mendeleev predicted its existence and some of its properties from its position on his periodic table, and called the element ekasilicon. On February 6, 1886, Clemens Winkler at Freiberg University found the new element, along with silver and sulfur, in the mineral argyrodite. Winkler named the element after Germany, his country ...
Gallium does not exist as a free element in the Earth's crust, and the few high-content minerals, such as gallite (CuGaS 2), are too rare to serve as a primary source. [55] The abundance in the Earth's crust is approximately 16.9 ppm. It is the 34th most abundant element in the crust. [56]