4.2 Shapes of alkanes The tetrahedral carbon atoms their chains are zigzagged(锯齿形) and not at all straight chains (E 链) Unbranched chain alkanes(直链烷烃) Branched chain alkanes(支链烷烃)4.2 Shapes of alkanes The tetrahedral carbon atoms their chains are zigzagged (锯齿形） and not at all straight chains （直 链） Unbranched chain alkanes (直链烷烃） Branched chain alkanes (支链烷烃）