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The periodic table 2 (Principles (Aufbau- When building up the electron…
The periodic table 2
Principles
- Aufbau- When building up the electron configuration of an atom in its ground state the electrons occupy the lowest available energy levels
- Hunds rule- When 2 or more orbitals of equal energy are available the electrons occupy them singly before filling them in pairs
- Pauli exclusion- no more than 2 electrons may occupy an orbital & they must have opposite spin
Francis Aston
- Used a mass spectrometer to measure the masses of atoms
- Atoms of the same element that have the same atomic number but different mass numbers
Mendeleev v Moseleys
- only 60 elements
- contains gaps
- over 100 elements
- no gaps present
Modern periodic table
- arrangement of elements in order of increasing atomic number
Modern periodic law
- When elements are arranged in order of increasing atomic number the properties of the elements recur periodically
Mass number
- The number of protons and neutrons in the nucleus of that atom
Relative atomic mass
- Average of the mass numbers of the isotopes of the element,
- as they occur naturally.
- Taking their abundances into account and
- expressed on a scale in which the atoms of the carbon 12 isotope have a mass of exactly 12 units
The mass spectrometer
5 main processes(VIASD)
- Vaporisation
- Ionisation
- Acceleration
- Separation
- Detection
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