IONIC BONDING

HOW DOES IT WORK? Ionic bonding takes place between metals and non-metals Metal atoms try to attain noble gas strucure (full outer shells) by losing electrons to form positive ions Non-metal atoms try to attain noble gas strucure (full outer shells) by gaining electrons to form negative ions The positive and negative ions formed attract each other to give an ionic bond.

Sodium Chloride

Sodium has atomic number 11 It therefore has 11 protons in its nucleus + + + + + + + + + + + It also has 11 electrons 2 in the inner shell 8 in the next shell 1 in the outer shell Sodium has 11 protons = 11 + charges Sodium has 11 electrons = 11 - charges Total = 0. It is a neutral atom

CHLORINE Chlorine has atomic number 17 The number of protons in its nucleus is 17 + + + + + + + + + + + + + + + + + The number of electrons is 17 In the inner shell 2 In the next shell 8 In the outer shell 7 Chlorine has 17 protons = 17 + charges It also has 17 electrons = 17 - charges TOTAL = 0. It is a neutral atom

- + Both Atoms want complete outer shells of electrons Sodium Atom Sodium Ion Chloride Ion Chorine Atom - + Sodium loses one electron to gain noble gas structure (complete outer shell) Chlorine gains the electron and also gets a complete outer shell of 8 electrons Now the sodium has 11protons (still) = 11+ charges The chlorine has 17protons (still) = 17+ charges But only 10 electrons = 10- charges But only 18 electrons = 18- charges Total = +1 which is the charge on the SODIUM ION Total = -1 which is the charge on the CHLORIDE ION

Magnesium Oxide

Magnesium has atomic Number 12 Oxygen has atomic Number 8 It therefore has 12 protons in the nucleus It therefore has 8 protons in the nucleus And 12 electrons arranged 2.8.2 And 8 electrons arranged 2.6 2+ 2- 8p 12p Magnesium needs to lose 2 electrons to get a complete outer shell Oxygen needs to gain 2 electrons to get a complete outer shell Magnesium still has 12 protons = 12+ But only 10 electrons = 10 – So overall charge = 2+ The ion is written Mg2+ Oxygen still has 8 protons = 8+ But now 10 electrons = 10 – So overall charge = 2- The ion is written O2-

Magnesium Fluoride

This gives us the Mg2+ ion And two F- ions MAGNESIUM FLUORINE Magnesium has atomic Number 12 Fluorine has atomic Number 9 It therefore has 12 protons in the nucleus It therefore has 9 protons in the nucleus And 12 electrons arranged 2.8.2 And 8 electrons arranged 2.7 8p 8p 12p Magnesium needs to lose 2 electrons to get a complete outer shell But Fluorine needs to gain only 1 electrons to get a complete outer shell Therefore another fluorine is needed This gives us the Mg2+ ion And two F- ions The formula is MgF2

IONIC STRUCTURES

Now opposite charges attract! POSITIVE ION NEGATIVE ION Now opposite charges attract! Positive ions and negative ions form a lattice . Every positive ion is surrounded by negative ions and every negative ion is surrounded by positive ions.

PROPERTIES OF IONIC COMPOUNDS They are crystalline solids They have high melting points Many dissolve in water If melted or dissolved in water, they conduct electricity. Salt Crystals (sodium chloride) Copper Sulphate crystals