1.2 Ions Understanding how electrons move inside an atom-how atoms react together-how has this helped develop artificial bones and wonder drugs?

Atoms and Ions Remember atoms are neutral? Why same no. of electrons and protons If we take an electron away or added…..they become charged as no longer equal We called a charged atom …AN ION Obviously if we remove an electron- POSITIVE CHARGE = cation If we add an electron = NEGATIVE CHARGE - anion

CATIONS Formed when an atom loses electrons usually from the outer shell- if it is empty more likely to form a cation Most often an atom loses all its outer electrons so only full shells remain

Cations cont: Cations usually come from metal atoms Metal atoms generally have few electrons in outermost shells so lose them easily as only weakly bound to the atom.

Non-metallic cations Or Mg2+ LOSES 2 ELECTRONS Hydrogen can form cations whenever acids are dissolved in bases- acids and bases are our next topic and this will make more sense! Cation symbols are made from the atomic symbol and the charge ie Na+ etc. Or Mg2+ LOSES 2 ELECTRONS

ANIONS Produced when atoms gain electrons Again occurs in outermost shell if it is almost full- it gains electrons until it is full DRAW FROM PG 14 OF PEARSONS TEXT All anions come from non-metallic atoms Gain electrons in outer shell Symbols used similar to cations-chemical symbol and charge Cl-

Ionic Compounds When anions and cations come together they join in large compounds of crystal lattices I.e Table salt NaCl Naming ionic compounds is easy- its just the name of the cation followed by the anion E.g, Sodium chloride Chemical formula can be slightly more difficult-there must be an equal number of positive and negative charges so the total is neutral or Zero.

Chemical Formulas In NaCl the charges are not shown as it is 1 positive and 1 negative so already is zero Magnesium Chloride is more difficult Magnesium has 2 positive charges and Chloride 1 Negative Mg2+ and Cl – To balance we need two Chloride ions so it is written as: MgCl2

Ionic Bonding Cations and anions are attracted to one another……awwww Due to the opposite charges When the charged ions come together they “stick” to each other forming an ionic bond These bonds hold together the crystal lattices: Therefore they are: Hard-need force to break Brittle-bonds hold the lattice in fixed positions so will shatter before it bends Have high melting points-it needs lots of heat/high temp to break the bonds and let the ions flow free Ionic compounds are often bright colours

Ionic compounds

Ions in Solution Some compounds dissolve in water Some do not How well the dissolve =their solubility When ionic compounds dissolve they “charge” the water around them as they produce cations and anions-the lattice breaks apart, the ions can not re-join and they spread evenly in the solution If the solution is heated to evaporation point they can re-join as the water is removed-re- crystallisation When ions are in solution it can conduct electricity

Epsom salt crystal

practical Pg 19 MAKING IONIC COMPOUNDS- PRAC IN FOLDER