Ionic Bonding

Electron Arrangement & Reactivity Noble gases are very un-reactive and have filled outer electron shells. Elements will seek to have a filled outer electron shell (like noble gases) by losing or gaining electrons. When an element loses or gains an electron it becomes known as an ION. Elements which lose electrons become positive Ions. Elements which gain electrons become negative Ions.

Ionic Bonding Example : Sodium and Chlorine Sodium will lose an electron to achieve a filled outer electron shell. Chlorine will gain an electron to achieve a filled outer electron shell The compound formed is Sodium Chloride, with a Chemical formula of Na 2,8,1 ==== Na+ 2,8 Cl 2,8,7 ==== Cl- 2,8,8 Therefore, Sodium Chloride is Na+Cl- {Now complete examples for : } Magnesium & Chlorine Sodium & Oxygen

A Quicker way to Write Ionic Formula From the position of an element in the periodic table we can tell at a glance the number of electrons in the outer shell, hence the Ion charge. Sodium (Na) = group 1 = 1e- in outer shell = 1+ charge Sulphur (S) = group 6 = 6e- in outer shell = 2- charge Eg {Now write the formula for Aluminium Fluoride and Sodium Oxide}

Transition Metal Compounds :Ionic Bonding It is difficult to predict the charge that is present on a Transition metal ion. To overcome this transition metal compounds always have the charge of the metal ion written into the name. Eg Iron (II) Oxide = Fe2+O2- Gold (III) Chloride = Au3+(Cl-)3

Compounds with more than two elements These compounds are known as COMPLEX IONS. The formula for these Ions is found on page 4 of your data book. Eg Magnesium Nitrate = Mg2+(NO3-)2 Sodium Sulphate = (Na+)2SO42- Ammonium Phosphate = (NH4+)3PO43-

Evidence for the Existence of ions. We tested a solution of Copper Chloride to Investigate the ions present. Observations Bubbles of Chlorine gas appear at the positive electrode (ANODE) Brown Copper metal is deposited at the negative electrode (CATHODE) Conclusions Chlorine must have a negative charge as it is attracted to the anode Copper must have a positive charge as it is attracted to the cathode.

Summary of Ions & Ionic Bonding Atoms wish to have the electron arrangement of Noble Gases. When an atom loses or gains an electron they become IONS. Metal atoms form positively charged ions : Mg2+ Na+ Non- metal atoms form negatively charged ions : O2- Cl- When a metal ion and non-metal ion come together they form ionic bonds, through the transfer of electrons.

Coloured Ionic Solutions. Ionic solutions can have a distinct colour. The colour of the solution is determined by the TRANSITION METAL ION present.