They are used in the treatment of bipolar disorder, where they have a role in treating depression and mania and may reduce the chances of suicide. Lithium salts are used in the pharmacology industry as mood stabilising drugs. Lithium is the 33rd most abundant element on earth, occurring in concentrations of between 20 and 70 ppm by weight, but due to its high reactivity it is only found naturally in compounds. Lithium is one of the few elements synthesized in the Big Bang. With a density of 0.564 g⋅cm −3, lithium is the lightest metal and the least dense solid element. At standard temperature and pressure, lithium is a soft, silver-white, highly reactive metal. Lithium is the first alkali metal in the periodic table, and the first metal of any kind in the periodic table. In ionic compounds, lithium loses an electron to become positively charged, forming the cation Li +. The two make up all natural occurrence of lithium on Earth, although further isotopes have been synthesized. Lithium (Li) is an alkali metal with atomic number 3, occurring naturally in two isotopes: 6Li and 7Li. The period shares this trait with periods 1 and 3, none of which contain transition elements or inner transition elements, which often vary from the rule. Īll period 2 elements completely obey the Madelung rule in period 2, lithium and beryllium fill the 2s subshell, and boron, carbon, nitrogen, oxygen, fluorine, and neon fill the 2p subshell. The elements in period 2 often have the most extreme properties in their respective groups for example, fluorine is the most reactive halogen, neon is the most inert noble gas, and lithium is the least reactive alkali metal. It also has the most number of nonmetals, namely five, among all periods. Period 2 only has two metals (lithium and beryllium) of eight elements, less than for any subsequent period both by number and by proportion. For all elements in period 2, as the atomic number increases, the atomic radius of the elements decreases, the electronegativity increases, and the ionization energy increases. Period 2 has much more conclusive trends. Period 1, which only contains two elements ( hydrogen and helium), is too small to draw any conclusive trends from it, especially because the two elements behave nothing like other s-block elements. Period 2 is the first period in the periodic table from which periodic trends can be drawn. Period 2 elements (carbon, nitrogen, oxygen, fluorine and neon) obey the octet rule in that they need eight electrons to complete their valence shell (lithium and beryllium obey duet rule, boron is electron deficient.), where at most eight electrons can be accommodated: two in the 2s orbital and six in the 2p subshell.Ĭalculated atomic radii of period 2 elements in picometers. In a quantum mechanical description of atomic structure, this period corresponds to the filling of the second ( n = 2) shell, more specifically its 2s and 2p subshells. The second period contains the elements lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, and neon. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behavior of the elements as their atomic number increases a new row is started when chemical behavior begins to repeat, creating columns of elements with similar properties. A period 2 element is one of the chemical elements in the second row (or period) of the periodic table of the chemical elements.
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