CI 2.1 &CI 2.3
- Created by: Leena
- Created on: 14-08-15 09:55
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- ATOMS
- All matter is composed of tiny particles called atoms.
- 3 Main Components
- Proton
- Equal to the number of electrons in a neutral atom.
- Number of protons - Identifies the element
- Relative Mass = 1
- Relative Charge = +1
- Electron
- Equal to the number of protons in a neutral atom,
- Relative Mass = 1/1836
- Relative Charge = -1
- Arranged in energy levels or shells.
- Each shell has a number - quantum number n
- The higher the value of n, the further the shell is from the nucleus and the higher the energy associated with the shell.
- Each shell can hold a fixed number of electrons.
- 1st shell - n=1 - 2 electrons.
- 2nd shell - n=2 - 8 electrons
- 3rd shell - n=3 - 18 electrons
- 4th shell - n=4 - 32 electrons
- Examples of rule breakers
- Potassium, 19K - 2.8.8.1
- Calcium, 20Ca - 2.8.8.2
- Scandium, 21Sc - 2.8.9.2
- Titanium, 22Ti - 2.8.10.2
- Electron configurations not as expected - resulting from overlap of energy levels within shells 3 &4.
- Electrons 19 & 20 have more stability if placed in shell 4 rather than shell 3.
- Each shell has a number - quantum number n
- Neutron
- Relative Mass = 1
- Relative Charge = 0
- Proton
- Ions
- Atoms which have gained or lost one or more electrons resulting in an overall +ve or -ve charge.
- Anion (-ve ion)
- Has gained electrons/ more electrons than protons.
- Cation (+ve ion)
- Has lost electrons/ fewer electrons than protons
- Isotopes
- Atoms of the same element with the same number of protons but different number of neutrons/mass number
- Chemically identical but have different physical properties - e.g mass, density, mp/bp.
- Relative Atomic Mass, Ar
- Average mass of an atom relative to the mass of 12C=12 - from the weighted average of the atomic masses of the naturally occurring isotopes of element.
- Calculation
- -Multiply isotopic mass by % abundance for each isotope - Add up these totals - Divide by total abundances.
- Mass Number, A
- Number of protons + neutrons in the nucleus.
- Atomic Number, Z
- Number of protons in the nucleus
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