The Bricks of Life: Exploring the Idea of Alien Chemistry

This article attempts to answer whether alien life is/was carbon based. The article then goes on about why carbon based life is what it is today on earth. For instance, that the carbon atom has four atoms on its outer shell, allowing it to bind with four other atoms or molecules. Looking at methane, a carbon atom is attached to four hydrogen atoms making its octet half full and half empty. Hence, this allows carbon to bind to other molecules instead of hydrogens. The article continues by emphasizing how well carbon is at making complex molecules and how these molecules are essential for starting and developing biological life.
http://www.space.com/searchforlife/seti_carbon_040415.html