![]() There are some elements like Boron, Beryllium, Aluminum, Hydrogen, Helium, and Lithium that do not complete octet in their valence shell and become stable without eight electrons.Į.g.: Boron and Aluminum become stable with only six electrons on their valence shell. Hydrogen and helium are subject to the duplet rule. By gaining, losing, or sharing electrons, the atoms acquire the electronic configuration of the nearest noble gas. Hence this tendency of elements to form a chemical combinations and get stability. Similarly, hydrogen has only one electron in its outermost shell i.e one valence electron.Įlements having incomplete octets in their valence shell try to get inert gas configuration by transfer or mutual sharing of valence electrons. For example, boron has three electrons in its outermost shell which means boron has three valence electrons. They are either transferred or shared (completely or partially) for the bond formation. Valence electrons are those electrons that are present in the outermost shell of an atom and take part in chemical bonding. The central boron atom is surrounded by three hydrogen atoms to form a covalent bond. The electronegativity of the boron atom (2.04) is lower than the hydrogen atom (2.20) and it acts as a central atom. ![]() In a BH 3 molecule in which one boron atom shares valence electrons with three hydrogen atoms. A dot represents a lone pair of electrons and a straight line represents a bond pair of electrons. It provides information about the bond pair and lone pair of electrons in a molecule. It is a simple diagrammatic representation of molecule atoms bonding. The Lewis structure of the molecule is also known as the electron dot structure. Hence, in this stage BH 3 molecule is highly unstable and dimerized (B 2H 6) and gets stability. As a result, boron atom fails to complete its octet. So boron covalently combines with three hydrogens and share electrons with each other gains extra three electrons on boron fills six electrons in its outermost shell. Similarly, hydrogen has only one valence electron on its outermost shell. As we know that boron is the central atom and has only 3 electrons on outermost shell. In BH 3 molecule, Boron atom has an incomplete octet which can be understood by counting the valence electron of boron atom. Why borane is a highly unstable and reactive substance? ![]() It is widely used in the synthesis of many organic compounds.Borohydride ion is considered to be its conjugate acid.It is highly unstable in nature and therefore highly reactive.Molecular mass of BH 3 is around 13.83g/mol -1.As a result, three bonds formed in the trigonal planar shape. It is commonly known as borane.īorane gas molecule consists of a single boron atom which is surrounded by three hydrogen atoms. Trihydridoboron with molecular formula BH 3 is a highly reactive in nature and highly unstable substance.
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