CBSE Class 10 Science 2019 · Paper 31/2/1 · Question 3

Molecular formula of ethene: ${\text{C}}_2{\text{H}}_4$. Electron dot structure: the two carbon atoms share two pairs of electrons (a carbon-carbon double bond), and each carbon shares one pair with each of its two hydrogen atoms, so each carbon has an octet and each hydrogen a duplet (dots are carbon electrons, crosses hydrogen electrons): $$\begin{array}{ccc}\text{H}& & \text{H}\\ \bullet \times & & \bullet \times \\ \text{C}& \begin{array}{c}\bullet \bullet \\ \bullet \bullet \end{array}& \text{C}\\ \bullet \times & & \bullet \times \\ \text{H}& & \text{H}\end{array}$$ Structural formula: ${\text{H}}_2{\text{C=CH}}_2$.