## Chemistry: The Central Science (13th Edition)

The Lewis symbol for $Sn^{2+}$ is seen in the diagram.
RULES TO WRITE LEWIS SYMBOL - Find out the number of valence electrons in the atom. - Write the element symbol and around it present each valence electron with one dot to the top, bottom, right or left of that symbol. - Spread out the dots as much as possible (so there would be minimum electron-electron repulsions), and no spots can hold over 2 electrons. 1) $Sn$ is in group 4A, so a neutral $Sn$ atom has 4 electrons in the outermost occupied shell. However, cation $Sn^{2+}$ already loses 2 electrons compared with its neutral $Sn$ atom. So, $Sn^{2+}$ only has 2 electrons in the outermost occupied shell. That means $Sn^{2+}$ has 2 valence electrons. The Lewis symbol of $Sn^{2+}$ would have 2 dots. 2) The dots must spread out as much as possible. So each of the 2 dots would occupy a spot of its own. Eventually, there are 2 spots with 1 electron, and 2 empty spots.