C₄H₁₀ is an alkane called butane. Knowing that it's an alkane, all the bonds involved here are single bonds. Each bond consist of 2 shared electrons. To obey the Octet Rule, each carbon atom must have 8 surrounding electrons. No need for the electron dots because the hydrogen bonds completed the octet rule. The first structure is the straight-chained butane. The second structure is the y-chained isobutane.
