What is the primary component of window glass?

Window glass is primarily composed of silicates, particularly silica (SiO2), which is derived from sand. Silica makes up the bulk of the glass structure because it provides the necessary glass-forming framework. When combined with small amounts of other materials, such as sodium carbonate (to lower the melting point) and lime (calcium oxide, to improve durability), silicates create a versatile and transparent material useful in making windows.

The other components listed do have specific roles in various types of glass, but they are not the primary constituent of standard window glass. For example, zinc oxide is used in certain optical glasses and ceramics and helps with properties like UV absorption, but it doesn't form the main structure of window glass. Borosilicate glass is designed to withstand high thermal stress and is typically used in laboratory glassware and cooktops. Calcium carbonate can be a component during the manufacturing process to provide lime, but it is not the primary ingredient in the final product. Therefore, silicates are indeed the most accurate answer regarding the primary component of window glass.