Covalent Bonding Flashcards
How is a covalent bond formed?
By sharing a pair of electrons to make a full outer shell of electrons
How are covalent substances bonded?
Atoms within a molecule are held together by very strong covalent bonds, but forces of attraction between molecules are weak. Due to these weak intermolecular forces, melting and boiling points are very low, because there is little energy needed to overcome these bonds
Why does the boiling point of simple molecular substances increase as Mr increases?
There are more points along the large molecules for intermolecular forces to act between them, so more energy is needed to break the forces.
Why do giant covalent structures have high melting points?
All atoms are bonded together by strong covalent bonds. A lot of energy is needed to overcome these strong covalent bonds, hence high melting and boiling points.
What are the properties of giant covalent structures?
They don’t conduct electricity even when molten and are often insoluble in water.
What is the structure of diamond?
Tetrahedral structure, where each carbon atom is joined to four others all with strong covalent bonds. This means a lot of energy is needed to overcome these bonds, so diamond has high melting and boiling points. These bonds also hold diamond in a very rigid structure, making it very hard. It doesn’t conduct electricity because it has no free electrons or ions.
What is the structure of graphite?
Each carbon atoms forms 3 bonds, creating hexagonal layers of carbon atoms. The layers are held together by weak intermolecular forces and can Slide Over each other, making graphite soft and slippery. High melting point - covalent bonds need lots of energy to break. Only 3 electrons used in bonds, so graphite has a sea of delocalised electrons between layers so can conduct electricity.
What is the structure of buckminsterfullerene?
Made up of 60 carbon atoms. Isn’t a giant covalent structure, just made up of large covalent molecules. Only held together by IM forces so can Slide Over each other. Each carbon has one delocalised electron, but electrons can move between molecules, so poor conductor of electricity.
