The structural formula of s-allylcysteine is shown in the picture (top figure). To create its Lewis structure, draw all its bonds between elements. Each single bond contains two electrons. There is an octet rule that must be obeyed by most elements. Each element should be surrounded with 8 electrons. The hydrogen is exempted of this rule. So, there are 4 lone pairs for the S atom, 1 lone pair for the N atom, and 2 lone pairs each for the 2 O atoms.
