04/01/12EdExcel Additional Science Chemical Structures W Richards The Weald School
Compounds 04/01/12Compounds are formedwhen two or moreelements arechemically combined.Some examples: Methane Sodium chloride (salt) Glucose
Some simple compounds… 04/01/12 CarbonMethane, CH4 Water, H2O dioxide, CO2 Key Hydrogen OxygenEthyne, C2H2 Sulphuric Carbon acid, H2SO4 Sulphur
Bonding Revision 04/01/12Cl Hi. My name’s Johnny Chlorine. I’m in Group 7, so I have 7 electrons in my outer shell Cl I’d quite like to have a full outer shell. To do this I need to GAIN an electron. Who can help me?
Ionic Bonding Revision 04/01/12Cl Here comes my friend again, Sophie Sodium Na Hey Johnny. I’m in Group 1 so I have one electron in my outer shell. Unlike Harry, this electron is far away from the nucleus so I’m quite happy to get Okay rid of it. Do you want it? - + Cl Na Now we’ve both got full outer shells and we’ve both gained a charge. We’ve formed an IONIC bond.
Covalent Bonding 04/01/12Cl Here comes another one of my friends, Harry Hydrogen Hey Johnny. I’ve only got one electron but it’s really close to H my nucleus so I don’t want to lose it. Fancy sharing? Cl H Now we’re both really stable. We’ve formed a covalent bond.
Covalent bonding 04/01/12Consider an atom of hydrogen: Notice that hydrogen has just __ electron in its outer shell. A full (inner) shell would have __ electrons, so two hydrogen atoms get together and “_____” their electrons: Now they both have a ____ outer shell and are more _____. The formula for this molecule is H2.When two or more atoms bond by sharing electrons wecall it ____________ BONDING. This type of bondingnormally occurs between _______ atoms. It causes theatoms in a molecule to be held together very stronglybut there are ____ forces between individual molecules.This is why covalently-bonded molecules have low meltingand boiling points (i.e. they are usually ____ or ______). Words – gas, covalent, non-metal, 1, 2, liquid, share, full, weak, stable
Dot and Cross Diagrams 04/01/12 Water, H2O: HH O
The Halogens - Chlorine 04/01/12 Each molecule has a strong force holding the atoms together, but the forces between molecules are very weak so chlorine is a gas at room temperature
The Halogens - Bromine 04/01/12 The forces between molecules are slightly stronger so bromine is a liquid at room temperature.
The Halogens - Iodine 04/01/12Iodine is a solid at room temperature but with gentleheating it will melt. The atoms will remain in pairs.
Forms of Carbon 04/01/12 1) Diamond – very hard, doesn’t conduct electricity, very high melting point2) Graphite – soft, does conductelectricity, very high melting point 3) Buckminsterfullerene – 60 carbon atoms arranged in a sphere
Metals 04/01/12 + + +Metals are defined as elements that readilylose electrons to form positive ions. There + + +are a number of ways of drawing them: + + + - - + + + + + + - - + + + + - - + + + - + + + - Delocalised electrons
Nanoscience 04/01/12 Nanoscience is a new branch of science that refers to structures built from a few hundred atoms and are 1-100nm big. They show different properties to the same materials in bulk. They also have a large surface area to volume ratio and their properties could lead to new developments in computers, building materials etc.Task: research nanoscienceand find two current and/orfuture applications of thisscience.
04/01/12Different ways of modelling atoms H N H H N H H H
Chemical-based Therapy 04/01/12Chemical-based therapy is the use of chemicals to alleviate anillness. Here are two examples:Chemotherapy – drugs that are used to kill cancer cellsAntibiotics – drugs that are used to kill bacteria that causeillnesses such as tuberculosis and cholera
Homeopathy 04/01/12Homeopathic medicines are drugs that contain compoundsthat, if strong enough, would cause an illness. These drugsinduce symptoms so that the body is “kick-started” intostarting the natural healing process.