structure diagram of hydrogen arsenate anion

hydrogen arsenate anion | structure diagram

Draw the Lewis structure of hydrogen arsenate anion. Start by drawing the overall structure of the molecule, ignoring potential double and triple bonds: Count the total valence electrons of the arsenic (n_As, val = 5), hydrogen (n_H, val = 1), and oxygen (n_O, val = 6) atoms, including the net charge: n_As, val + n_H, val + 4 n_O, val - n_charge = 32 Calculate the number of electrons needed to completely fill the valence shells for arsenic (n_As, full = 8), hydrogen (n_H, full = 2), and oxygen (n_O, full = 8): n_As, full + n_H, full + 4 n_O, full = 42 Subtracting these two numbers shows that 42 - 32 = 10 bonding electrons are needed. Each bond has two electrons, so we expect that the above diagram has all the necessary bonds. However, to minimize formal charge oxygen wants 2 bonds. Identify the atoms that want additional bonds and the number of electrons remaining on each atom. The net charge has been given to the most electronegative atom, oxygen, in 2 places: In order to minimize their formal charge, atoms with large electronegativities can force atoms with smaller electronegativities on period 3 or higher to expand their valence shells. The electronegativities of the atoms are 2.18 (arsenic), 2.20 (hydrogen), and 3.44 (oxygen). Because the electronegativity of arsenic is smaller than the electronegativity of oxygen, expand the valence shell of arsenic to 5 bonds (the maximum number of bonds it can accomodate). Therefore we add a total of 1 bond to the diagram, noting the formal charges of the atoms. Double bonding arsenic to the other highlighted oxygen atoms would result in an equivalent molecule: Answer: | |