TSR Wiki > Study Help > Subjects and Revision > Revision Notes > Chemistry > General Equations and Definitions
- Atomic Masses = the number of protons and neutrons
- Atomic Number = number of protons and therefore also the number electrons
- Electron Shielding = This is where electrons in the inner shells of a atom stop the full charge of the nucleus effect electrons outside that shell, e.g. if a shell has 6 electrons it will reduce the effective nuclear charge by 6+.
- Enthalpy = This is the energy change of a substance per mole.
| Particles in the atom
| Charge in Coulombs
| Mass in Kg
| Relative Charge
| Relative mass
|
| P proton
| 1.602 x 10–9
| 1.672 x 10-27
| +1
| 1
|
| N neutron
| 0
| 1.675 x 10-27
| 0
| 1
|
| E electron
| 1.602 x 10–9
| 9.109 x 10-31
| -1
| 1/1836
|
- Energy Transfer = Mass ´ Specific heat capacity ´Temperature change
- Energy Transferred = M x C x DT
- For enthalpy divide by the number of moles.
- Concentration = moles / volume
- Working out formula by percentage using RAM, divide the percentage by the RAM, E.g. for 22.02% of Carbon(12), 4.59% of hydrogen(1), 73.39% of Bromide(80): we get:
- 22.02 / 12 = ~ 2; 4.59 / 1= ~ 5; 73.39 / 80 = ~ 1 \ C2 H5 Br
- At 20°C; 1 mole of gas will occupy 24 dm3, this is the R.T.P.
- At 0°C; 1 mole of gas will occupy 22.414 dm3, this is the S.T.P.
Radioactive Decay
| Radio Active Decay
| Basically what happens
| Example
|
 (alpha ) decay
| The release of a helium nucleus
(2 P and 2N) from the nucleus
| 
|
 (beta) decay
| A neutron decomposes to create a
electron and proton, the electron is
then expelled from the nucleus
| 
|
 Gamma Decay
| The nucleus has too much energy,
which makes it unstable, so a pulse
of energy is expelled from the nucleus
| -
|
| Fission
| Where a large atom decomposes into
two smaller atoms and sometimes some
other neutrons are released
| 
|
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