# Ionic Compounds Recall Ions: -“+” on the left (metals) because they lose electrons (become less negative) - “-” on the right (non-metals) because they.

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Ionic Compounds Recall Ions: -“+” on the left (metals) because they lose electrons (become less negative) - “-” on the right (non-metals) because they gain electrons (become more negative) -What is the total charge if you have X +1 and Y -1 -______________________________________

Ionic Compounds Metal and a non-metal combine to form "Ionic Compounds". The metal atoms loses electrons to form positive ions. The non-metal gains the electrons to form negative ions. The two ions join together ______________________________________

Ionic Compounds Ionic compounds are formed when a metal gives one or more of its electrons to a non metal. When all of the electrons are gone, the metal’s inner orbit of electrons is full. So, the metal is stable. ______ Ca Ca +2

Ionic Compounds The non-metal receives one or more electrons to fill its outer shell and become stable. If we draw the Lewis Structure for a non metal we include the full valence orbit, brackets and a charge Having gained two electrons, the Oxygen is now negative. ____ O O -2

Ionic Compounds Putting the compound together, we can see that the overall molecule has a neutral charge. This particular example is simple because the Calcium and Oxygen want to exchange the same number of electrons. What would happen if they wanted to exchange different numbers of electrons? O -2 Ca +2 +2 – 2 = 0 Try it!

Using Lewis Structures: Ionic bonding between Lithium and Oxygen 1.First draw the Lewis structures of the atoms on their own. 2.Now use an arrow to show the electron transferring from the Lithium atom to the Oxygen atom 3.You can see that the Oxygen atom still does not have a complete outer shell. Clearly another Lithium atom is required to complete the compound. Li O

Lithium Oxide continued ______________________ The final Lewis structure is illustrated here. ______________________ Li + O -2

Illustrate the bonding between Aluminum and Oxygen. (Note the ratio here is a little harder to find.) Draw the Lewis Structures of the individual atoms. Use arrows to show the transfer of electrons. Aluminum has one electron left, we need another oxygen atom. The oxygen atom now needs more electrons so we need another aluminum atom. The extra electrons on the Aluminum mean we need another Oxygen. Since, we have been able to make both atoms stable, we have hit the correct ratio. Al OOO

Aluminum Oxide Continued Having _______3 electrons, the aluminum has a charge of __. Having ________2 electrons, the oxygen has a charge of ___. Now draw the final Lewis Structure. This structure is designed to illustrate the transfer of electrons while bonding. O -2 O O Al +3

Naming Ionic Compounds Naming these compounds is straight forward. 1.______________________ 2.______________________ Examples – Sodium Chloride, Calcium Oxide

Writing the formulas for Ionic Compounds The trick to finding the ratio of atoms in the molecule. The easiest way is to find the number of BONDS the ion will make is to again refer to your period table

Writing the formulas for Ionic Compounds 1.Number the groups 1-3 going from left to right (skip the Tansition Metals) 2.Number the groups 1-3 going from right to left (skip the Nobel Gases) 1 2 3 321

Writing the formulas for Ionic Compounds ______________________ +1 +3-3-2 +2

Then … Write out the atoms with their stable charge Al +3 O -2 Cross over the numbers to the opposite atom (Criss- Cross Rule!) Al 2 O 3 ____

Example: Aluminum Chloride Step 1: AluminumChloride Step 2: Al +3 Cl -1 Step 3: Al Cl 13 Step 4: AlCl 3 Criss-Cross Rule write out name with space write symbols & valence number criss-cross valence number as subscripts combine as formula unit (“1” is never shown) - Reduce if possible

Example: Magnesium Oxide Step 1: Magnesium Oxide Step 2: Mg +2 O -2 Step 3: Mg O 22 Step 4: Mg 2 O 2 Step 5: MgO Criss-Cross Rule

Multivalent Compounds _____ When atoms get larger, their atomic structure can become more complex. This means that some atoms can have different numbers of valence electrons in different situations. For example if we look at the Lewis structure of Copper. It can have one valence electron or two valence electrons. Clearly, this atom can form more than one type of molecule. Cu Cu +1 O -2 Cu +2 O -2

Multivalent Compounds In terms of naming these compounds, we need a method of distinguishing, CuOand Cu 2 O ______________________ The roman numeral is only included if the metal is one of the atoms that can exhibit more than one charge. This information will be provided! e.g. Write the name for the following compounds, CuF Copper (I) Fluoride PbI 2 ______________________ CaF 2 ______________________

How do we know which roman numeral is being used? CuF -______________________ Cu 1 F 1 Cu +1 F -1 Copper (I) Flouride PbI 2 Pb 1 I 2 Pb +2 I -1 Lead (II) Iodide

________ Be careful when you are asked to determine the roman numeral given the formula (e.g. CuS) This would lead you to answer: Copper (I) Sulfide However we ALWAYS NEED TO CHECK THAT THE CHARGE ON THE ANION IS CORRECT In this case it would be -1 however, if we look at the periodic table we know that S is -2 Therefore we need to multiply both charges by 2 Copper (II) Sulfide __________

Ionic Compounds Many ionic compounds are soluble in water. When they dissolve, they separate into ions. Water molecules surround each ion preventing it them from rejoining

Ionic Compounds Properties ______________________ Many are also electrolytes which means they conduct electricity when dissolved in water Pure water is a poor conductor of electricity, dissolved ions improve this property considerably

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