Oxygen is the third most abundant element in the universe. It is made in stars which are 5 or more times heavier than the Sun, when they burn helium and carbon in nuclear fusion. Just five elements make up over 90 percent of the weight in the Earth’s crust. Almost half of the weight of the crust comes from oxygen. (Silicon, aluminum, iron and calcium are the other four main elements in the crust.) It is also a simple covalent molecule, formed by 2 oxygen atoms bonding covalently.

GCSE scientists – you need to be able to explain the properties of covalent compounds. Our new guide “How to work with Covalent Bonding: Part 2” will help you. It describes the properties of both simple covalent molecules, and giant covalent structures like diamond and graphite. Explanations of the reasons for the properties is included. It also includes questions, and answers for you to check your understanding.

Click on the picture below to see the guide.

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