Theory :
Theory Atoms gain / lose electrons to obtain FULL shells
Noble gas electronic structure is more stable
e.g 2 or 2,8 or 2,8,8
EASY to lose / gain 3 electrons or LESS !
Key Points :
Key Points Square brackets for EACH ion in the formula
Charge outside the bracket
Only the outer electrons shown
Example : NaCl :
Example : NaCl Two ions are present, therefore two atoms to start with : ATOMS: 2 , 8 , 1 2 , 8 , 7 IONS : 2 , 8 2 , 8 , 8
Exercise :
Exercise Draw the DOT and CROSS diagrams for :
MgO
Li2O
AlCl3
Al2O3 Hint :
Li = Group 1
Mg = Group 2
Al = Group 3
O = Group 6
Cl = Group 7