C1.7 - Ions, Atoms, Isotopes

• a particle which has either lost/gained electrons to gain an overall charge • protons are fixed in the nucleus so their number stays the same • if an atom gains an electron = negative charge • if an atom loses an electron = positive charge

• depends on number of electrons in the outer most shell • outer shell electrons are the most easily lost • Noble Gases do not react as they have a complete outer shell

-Group 1 /2/3 Elements always make a positive ion as the electron in the outer most shell is always lost as it is the minority -all metals form positive ions -all non-metals form negative ions -

Number of electrons in the outer most shell of the atom -excludes transition metals

• atoms of the same element always have the same number of protons but different number of neutrons • they are virtually identical in their reactions as the number of electrons remain unchanged

• melting points change • density changes • atomic mass

(% of isotope 1 x mass of isotope 1) + (% of isotope 2 x mass of isotope 2)