Chemical Bonding You are to research the following questions and choose an appropriate format to present your answers in. Include diagrams where possible. 1. Describe metallic, ionic and covalent bonds. Metallic – A chemical bond in which electrons are shared over many nuclei and electronic conduction occurs. Ionic – A chemical bond in which one atom loses an electron to form a positive ion and the other atom gains an electron to form a negative ion. Covalent – A chemical bond that involves sharing a pair of electrons between atoms in a molecule. . Explain the structure of metals, ionic compounds, covalent molecules and covalent networks and give examples of compounds and elements that have these structures. Metals – In a piece of metal, the outer shell of electrons are not closely to their own atoms. They leave their atoms, forming positively charged ions, and tend to wander from one atom to another, being shared by all the ions. We say that the atoms are delocalised meaning not held in their own locality or place. They form a sea of electrons within the metals.
The outer shell of electrons move freely so metals are good conductors of electricity, metal ions can slide over each other without breaking which makes metals malleable and ductile. The sea of electrons reflect light with gives metals a shiny lustre. (All Metals) Ionic Compounds – Ionic compounds is a compound that contains ions held together by ionic bonds. Most ionic compounds are crystalline solids at room temperature. An ionic compound consists of a three-dimensional lattice (network) of ions held together by ionic bonds, which extend throughout the whole crystal structure.
Ionic Compounds have high melting and boiling points because of the electrostatic bonds throughout their crystal lattice. Electrons are held firmly in ions so they are bad conductors of electricity when solid. When molten, the ion vibration and causes breaks in the electrostatic bonds, which make molten ionic compounds conductors of electricity. When dissolved in water, the water comes between electrostatic bonds, which conducts electricity. (Sodium Chloride, Hydroxides)
Covalent Molecules – A molecule made up of two nonmetals that share a pair of electrons between them. Most tend to have low melting and boiling points because the links between molecules are weak while links within each molecule is strong. These weak intermolecular forces are called dispersion forces. (Carbon, silicon) Covalent Lattices – Have extremely high melting and boiling points because of their strong covalent bonds extend throughout the network. For these substances to change, a great deal of energy is need to break the covalent bonds. . Describe the following physical properties of each structure (metals, ionic compounds, covalent molecules and covalent networks): * Hardness * Melting point * Solubility in water * Electrical conductivity (as a solid, as a liquid and in aqueous solution) | Metals| Ionic Compounds| Covalent Molecules| Covalent Networks| Harness| Dense | Dense| Soft| Dense| Melting point| High | High| Various| Various| Solubility (H2O)| No | Yes| Low| Low| Conductivity| High| Low (Solid)High (Molten & dissolved)| Low| Low|