Chapter 3 IONS and The Periodic Table

EXITIons Atoms acquire a charge by gaining or losing electrons – not protons!! Ion Charge = # protons – # electrons ions with a + charge are called cations – more protons than electrons – form by losing electrons ions with a – charge are called anions – more electrons than protons – form by gaining electrons 2

EXIT Atomic Structures of Ions Metals form cations For each positive charge the ion has 1 less electron than the neutral atom – Na atom = 11 p + and 11 e -, Na + ion = 11 p + and 10 e - – Ca atom = 20 p + and 20 e -, Ca 2+ ion = 20 p + and 18 e - Cations are named the same as the metal sodiumNa  Na + + 1e - sodium ion calciumCa  Ca e - calcium ion The charge on a cation can be determined from the Group number on the Periodic Table – Group 1A  +1, Group 2A  +2, (Al, Ga, In)  +3 3

EXIT Atomic Structures of Ions Nonmetals form anions For each negative charge the ion has 1 more electron than the neutral atom – F = 9 e -, F - = 10 e - – P = 15 e -, P 3- = 18 e - Anions are named by changing the ending of the name to -ide fluorineF + 1e -  F - fluoride ion oxygenO + 2e -  O 2- oxide ion The charge on an anion can be determined from the Group number on the Periodic Table – Group 7A  -1, Group 6A  -2 4

EXIT 5 Li +1 Na +1 K +1 Rb +1 Cs +1 Be +2 Mg +2 Ca +2 Sr +2 Ba +2 Al +3 Ga +3 In +3 O -2 S -2 Se -2 Te -2 F -1 Cl -1 Br -1 I -1 N -3 P -3 As Zn +2 Cd +2 Ag Common Ions