atomic number: number of protons in its nucleus
mass number : number of protons and neutrons in the nucleus
isotopes : atoms of the same elements with same atomic number but different mass number
relative atomic mass : weighted average mass of an atom of an element relative to 1/12 the mass of a C-12 atom
relative isotopic mass : mass of an atom of an isotope relative to 1/12 the mass of an C-12 atom
relative molecular mass : sum of the atomic masses of all the atoms in its molecular formula
the mass spectrometer
- the sample is injected into the mass spectrometer and first vaporised.
- the vapour is bombarded with high-energy electrons, which knock electron off atoms in the sample, forming positive ions.
- the ions are accelerated by an electric field.
- they pass through velocity selector, that make sure they are all travelling with same velocity.
- ions enter a uniform magnetic field. ion that is heavier, and with smaller positive charge will deflect less. ion that is lighter, and with bigger positive charge will deflect more.
ionization energy: energy needed to remove one electron from each atom in one mole of gaseous atoms to form one mole of singly positively charged gaseous ions.
factors affecting the i.e :
atomic radius (smaller, higher)
nuclear charge (higher, higher)
electron shielding (by inner electron)
second ionization energy: the energy required to remove 1 mole of electron from 1 mole of singly 1+ charged gaseous ions to form 1 mole of 2+ charged gaseous ions.
evidence of existence of the shell : difference in energy level ( in graph of i.e against number of electron removed) : big jump
*first ionization energy is the lowest because the electron is the furthest from the nucleus
*ionization energy generally increase across the period (but slightly decreased between Beryllium-Boron, Nitrogen-Oxygen, Magnesium-Aluminium, Phosphorus-Sulfur)