1. Identify the Elements
* Silicon (Si) is in Group 14 (IVA) of the periodic table.
* Oxygen (O) is in Group 16 (VIA) of the periodic table.
2. Determine the Number of Valence Electrons
* Silicon has 4 valence electrons (it's in Group 14).
* Oxygen has 6 valence electrons (it's in Group 16).
3. Determine the Desired Number of Bonds
* Silicon needs to form 4 bonds to achieve a stable octet (8 electrons in its outer shell).
* Oxygen needs to form 2 bonds to achieve a stable octet.
4. Find the Simplest Ratio
* To satisfy the bonding requirements, one silicon atom can bond with two oxygen atoms. This is represented by the formula SiO₂.
5. Write the Formula
* The formula of the covalent compound is written with the element that is less electronegative (in this case, silicon) first, followed by the element that is more electronegative (oxygen). The subscripts indicate the number of atoms of each element in the molecule.
Key Points:
* Covalent Compounds: Atoms share electrons to achieve stability.
* Electronegativity: A measure of an atom's ability to attract electrons. The more electronegative atom is typically written last in the formula.
* Octet Rule: Most atoms strive to have eight electrons in their outermost shell (except for hydrogen, which seeks two).
Let's look at another example:
Carbon Dioxide (CO₂)
* Carbon (Group 14) has 4 valence electrons.
* Oxygen (Group 16) has 6 valence electrons.
* One carbon atom can form double bonds with two oxygen atoms, satisfying the octet rule for all atoms.
Therefore, the formula for carbon dioxide is CO₂.
