Covalent Structures When ions come together into a larger structure it is called a ionic lattice. In covalent bonding, when the atoms (remember they have no charge so aren’t ions) come together they can either form a giant covalent substance or a simple molecular substance. Giant Covalent Substances Giant covalent substances have billions of atoms all joined up together by covalent bonds. Two examples are diamond (left) and silicon dioxide (right): Because covalent bonds are so strong, these substances are hard. Because a lot of energy is required to break the bonds, they also have high melting and boiling points. There are no free electrons or charged particles in these structures. Therefore they never conduct electricity. Silicon dioxide has a giant covalent structure. What would you expect its properties to be? Silicon dioxide is used to make moulds for pouring liquid metal into. Explain why silicon dioxide is used for this. Silicon carbide is a giant covalent substance. Explain why it has a high melting and boiling point. Aluminium iodide has a giant structure. Will it have a giant ionic or covalent structure? Explain your answer. State the conditions under which an ionic compound will conduct electricity. How many electrons does silicon have in its outer shell? How many neutrons does silicon have? What is the mass and charge on an electron? How did scientists prove that the plum pudding model of the atom must be incorrect? A student has a sample of two substances. One has a giant ionic lattice and the other is giant covalent. Why can the student not use their melting points to work out which is which? How could the student work out which one is which? What other differences are there between giant ionic and covalent structures. Graphite: the exception Graphite is a giant covalent structure made entirely of carbon atoms like diamond. However, its atoms are arranged differently meaning it has different properties. In what ways are graphite and diamond similar? State two differences between diamond and graphite Explain why graphite can conduct electricity What is the difference between an element and a compound?
Covalent Structures When ions come together into a larger structure it is called a ionic lattice. In covalent bonding, when the atoms (remember they have no charge so aren’t ions) come together they can either form a giant covalent substance or a simple molecular substance. Giant Covalent Substances Giant covalent substances have billions of atoms all joined up together by covalent bonds. Two examples are diamond (left) and silicon dioxide (right): Because covalent bonds are so strong, these substances are hard. Because a lot of energy is required to break the bonds, they also have high melting and boiling points. There are no free electrons or charged particles in these structures. Therefore they never conduct electricity. Silicon dioxide has a giant covalent structure. What would you expect its properties to be? Silicon dioxide is used to make moulds for pouring liquid metal into. Explain why silicon dioxide is used for this. Silicon carbide is a giant covalent substance. Explain why it has a high melting and boiling point. Aluminium iodide has a giant structure. Will it have a giant ionic or covalent structure? Explain your answer. State the conditions under which an ionic compound will conduct electricity. How many electrons does silicon have in its outer shell? How many neutrons does silicon have? What is the mass and charge on an electron? How did scientists prove that the plum pudding model of the atom must be incorrect? A student has a sample of two substances. One has a giant ionic lattice and the other is giant covalent. Why can the student not use their melting points to work out which is which? How could the student work out which one is which? What other differences are there between giant ionic and covalent structures. Graphite: the exception Graphite is a giant covalent structure made entirely of carbon atoms like diamond. However, its atoms are arranged differently meaning it has different properties. In what ways are graphite and diamond similar? State two differences between diamond and graphite Explain why graphite can conduct electricity What is the difference between an element and a compound?