Ionic Bonding What are the charges on the following ions? Na Ca Cl Al L.O. To be able to describe ionic bonding. To be able to explain the properties of ionic compounds. What are the charges on the following ions? Na Ca Cl Al Sr F As O Rb Kr

Very strong electrostatic attraction Ionic Bonding This is the net electrostatic attractions between oppositely charged ions. - + Cation Anion Very strong electrostatic attraction

How are ions formed? By atoms losing or gaining electrons More electronegative non-metal atoms GAIN electrons FROM metal atoms CATIONS (+) are formed when atoms (USUALLY METALS) lose electrons to non-metal ANIONS (-) are formed when atoms (USUALLY NON-METALS) gain electrons from metal Example Example Na - 1s22s22p63s1 F - 1s22s22p5 Na+ - 1s22s22p63s0 F- - 1s22s22p6 Ions are isoelectronic with nearest noble gas

Ionic Bonding Group 1-3 METALS :  1+ , 2+ and 3+ ions respectively  loss of ALL outer e- to non-metal, leaving noble gas structure ( - s2 p6 ) Group 5 - 7 NON-METALS :  3- , 2- and 1- ions respectively  by gain of e- from metal to form noble gas structure ( - s2 p6 ) Group 4 : No 4+ ions  too much energy to remove 4 e- No 4- ions  too much repulsion between 4 added e- Some 2+ ions  lower in group eg Sn2+ and Pb2+

Sodium chloride Na+Cl-(s) X 2 , 8 , 1 Cl X 2 , 8 , 7 Na+ 2 , 8 Cl- X 2 , 8 , 8 3D giant lattice with 1:1 ratio of ions to give electrical neutrality Na+Cl-(s)

Magnesium oxide Mg2+O2-(s) X 2 , 8 , 2 O X 2 , 6 O2- X 2 , 8 3D giant lattice with 1:1 ratio of ions to give electrical neutrality Mg2+ 2 , 8 Mg2+O2-(s)

Calcium fluoride  Ca2+ F-2(s) X F X 2 , 7 Ca 2 , 8, 8 , 2 F X 2 , 7 2 , 8 , 8  Ca2+ F-2(s)

Aluminium oxide (Al3+)2(O2-)3 2 , 8 , 3 O X 2 , 6 2 aluminium atoms transfer outer electrons (6 in total), 2 to each of 3 oxygen atoms O2- X 2 , 8 3D giant lattice with 2:3 ratio of ions to give electrical neutrality Al3+ 2 , 8 (Al3+)2(O2-)3

General Ionic Structure ions arrange in a giant lattice structure cations and anions arranged alternately 3-dimensional array lattice is very strong due to many ionic bonds

The Sodium Chloride Lattice = Na+ = Cl- Each sodium ion is surrounded by six chloride ions Each chloride ion is surrounded by six sodium ions  6:6 coordination  Na1Cl1 formula

Properties of ionic compounds How does the giant ionic lattice structure explain the characteristic properties of ionic compounds? - very strong inter-ionic forces to break very high melting point solid does not conduct electricity - ions cannot move conduct electricity when molten or in solution - ions free to move

Evidence for ions Teacher notes This virtual experiment illustrates how copper can be purified using electrolysis. It could be used as a precursor to running the practical in the lab or as a revision exercise.

Atomic vs Ionic radii The figure shows an electron density map for aluminium. The metallic radius for aluminium is 0.1nm. [1nm. = 10-9 m] The ionic radius for Al3+ is 0.045 nm. (4.5 x 10-11 m). Why is this so much smaller than the metallic radius?

Ionic radii The table below shows some values for ionic radii of atoms. Ion Radius (nm) Li+ 0.068 F- 0.133 Na+ 0.098 Cl- 0.181 K+ Br- 0.196 Rb+ 0.148 I- 0.219 The ionic radius of the cation (+ve ion) is less than that of the parent atom. Na = 0.157 nm Na+ = 0.098 nm The ionic radius of an anion (-ve ion) is greater than that of the parent atom. Br = 0.114 nm Br- = 0.196 nm   Ionic radii increase down a group Ionic radii decrease across a Period Na+ = 0.098 nm Mg2+ = 0.065 nm Al3+ = 0.045 nm N3- = 0.171 nm O2- = 0.146 nm F- = 0.133 nm