How to Determine How Many Dots Are on an Element's Lewis Dot Structure

Determine how many electrons to place on a Lewis Dot structure.
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Lewis dot structures simplify the method of indicating how bonding occurs in covalent molecules. Chemists use these diagrams to visualize the association of valence electrons between bonded atoms. To draw a Lewis dot structure for an atom, you must know how many valence electrons an atom possesses. The periodic table organizes the elements based on the similarity of their chemical properties. One of the properties associated with an element is the number of other atoms it forms molecules with and how many different bonds in which it can participate. The first two columns and the last six columns of the periodic table indicate the s and p orbitals that hold the valence electrons and participate in the formation of covalent bonds.

    Find the element on the periodic table. Lewis dot structures are simplified representations of the valence electrons for elements. The location on the periodic table will indicate how many valence electrons the element possesses.

    Draw the symbol for the element of interest. The valence shells for most elements have room for eight electrons except hydrogen and helium that can accommodate two electrons. Transition metals have room for 18 electrons but do not obey the octet rule obeyed by other elements. They form coordination complexes with other atoms.

    Identify the position for the valence shells on the element symbol. Place the electron orbitals on either side, above and below the element’s symbol for atoms that are involved in single bonds only. For molecules that have double bonds the orbitals are spaced 120 degrees apart with one of the three orbitals holding two electrons for the double bond. In the case of molecules that have triple bonds the molecule is linear and the side of the atom that is involved in the triple bond has three electrons. Each of the orbitals is capable of holding two electrons.

    Count the number of positions from the leftmost column of the periodic table to the position of the element. The first two columns and the last six columns of the table indicate the elements that possess valence electrons. The elements in the transition metal region of the table have valence electrons also but their bonding is more complicated than the other elements.

    Place the number of electrons that you determined into the orbitals around the element’s symbol. Place a single electron in each orbital before placing a second electron in another orbital. In molecules that posses double or triple bonds, the two or three electrons involved on both atoms involved in the double or triple bond are situated between the two atoms.

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