 atoms that are now stable because they have gained or lost valence electrons resulting a positively or negatively charged atom

 a type of chemical bond formed between ions with opposite charges (+ and -)  therefore, it is mostly elements from the left side of the periodic table combining with those from the right side + -

 always the same elements in the same proportion  ex- NaCl (1:1)  CaCl 2 (1:2)  Al 2 O 3 (2:3)

 atoms gain or lose valence electrons in order to have a full valence shell (2 or 8)  ex) Na has one valence electron, therefore it would lose it and be +1 charged (this is referred to as its ionic charge )  ex) O has six valence electrons, therefore it would gain two and be -2 charged

++ -- e-

Na gives Cl one electron and now both atoms are stable

 it is easier to just draw Lewis-dot structures to show valence electrons instead of the drawing the whole atom

 An oxidation number indicates the charge on the atom (or ion) when electrons are lost, gained, or shared in chemical bonds  the oxidation numbers for all the atoms in a compound must add up to zero

...etc. As it turns out, atoms bond together for a very simple reason: atoms like to have full valence shells (2 or 8) /-2-1-0

 sometimes it takes more than one of each atom to make the compound “work”  Mg and Cl?  it takes two chlorines to combine with one magnesium  MgCl 2 → magnesium chloride

 Mg and N?  it takes two nitrogens to combine with three magnesiums  Mg 3 N 2  magnesium nitride

 Easiest way is to switch the charge numbers and write them as subscripts on the formula. Be +2 and N 3- Be 3 N 2 beryllium nitride

 there is only one way ions can combine, therefore there is only one name for each compound formed  keep the first element’s name the same  change the second element ending to ide  sodium and chlorine (NaCl) becomes…  sodium chloride  magnesium and fluorine (MgF 2 )….  magnesium fluoride  K and P (K 3 P)  potassium phosphide