Currently unavailable: for new students
Degree: MChem (Masters) - Oxford, St Catherine's College University
|Chemistry||A Level||£20 /hr|
|Before 12pm||12pm - 5pm||After 5pm|
Please get in touch for more detailed availability
There are 2 types of bonding in chemicals; ionic bonding and covalent bonding. Both of these aim to fill the outer shells of the atoms. You can also have bonds between molecules called intramolecular bonds.
Ionic bonding is where the electrons involved in the bond are fully transferred from one species to another in order to fill the outer shell of all the atoms involved. This creates some ions which are positively charged, and some which are negatively charged, and their is an electrostatic attraction between the opposite charges.
For example, in table salt, NaCl, the sodium fully transfers one if it's electrons to the chlorine to make Na+ and Cl- which attract each other to form NaCl.
Covalent bonds are when the species involved share some of their electrons with each other so that both species fill their outer shells.
For example, in hydrogen, each hydrogen atom on it's own only has 1 electron in it's outer shell. To fill it, they need 2, so they each share their single electron with the other, so that both hydrogen atoms have access to both electrons, therefore having full outer shells and making H2.see more
Isotopes are different forms of the same element by mass. While an atom is classified as a particular element based on the number of protons in the nucleus, the specific isotope of that element is determined by the number of neutrons in the nucleus.
Chlorine is reported as having a relative atomic mass of 35.5. This is because chlorine actually has 2 isotopes, Cl35 and Cl37. The figure of 35.5 is an average of these two, weighted by natural abundance.
Both of these isotopes have 17 protons, which defines them as chlorine atoms, but the Cl35 has 22 neutrons, whereas the Cl37 has 24.see more
Enthalpy (given the symbol H) is a measure of how much heat energy can be released by a chemical. ΔH is defined as the amount of heat energy released or taken in when two chemicals react. If ΔH is negative it means that the reaction is exothermic and will give out heat as it progresses and will feel hot.
If ΔH is positive then the reaction is endothermic and will therefore absorb heat as it progresses, and will feel cold.see more