1. ACCESS CHEMISTRY Week 3 ionic bonding Are you ready to learn? Lab notebook out and a pen No food out, drinks away Phones on silent and in your bag Bags and coats under bench or at the back. Starter – match up the correct spdf electronic configuration to the element

2. LEARNING AIMS  Recall spdf configuration  Define how stability occurs when elements chemically combine and energy is lowered  Define the formation of ions  Predict the structure of ions  Show the bonding that occurs between ions in an ionic bond  Recall elements, compounds and mixtures  Be able to separate substance by their physical properties News!

3. BEEN...................NOW................NEXT Elements and how electrons are arranged how some elements form ions How elements chemically reform new compounds by ionic bonding We have seen how the electrons are arranged We have looked at how when elements chemically combine together they form compounds. These take on many forms sometimes giant structures, sometimes small individual clusters. These individual clusters are called MOLECULES. When we get more than one atom bonded together with another atom we often call this a molecule for example oxygen, chlorine, nitrogen.

4. THE VALENCE ELECTRONS  The outer most electrons of an atom are sometimes called the valence electrons  These are the electrons that are involved in bonding and determine the chemical behaviour of the element.  In the periodic table the main group elements are arranged in vertical groups containing elements with the same number of valence electrons. These elements have similar chemical properties.  The atoms tend to obtain a maximum number of 8 in the outer shell, so if we have nitrogen in group 5, with 5 electrons in the outer shell, it requires 3 more electrons to take it up to 8, and so on…

5. SPDF NOTATION & VALENCY: Try and fill in the table on p 10 of your workbook n= 1 n= 2 n= 3 n= 4 n= 5 n= 6 n= 7 34563456 4554555 GROUPS PERIODSPERIODS

6. IONS  When a valence electrons are drawn by electrostatic attraction of one atom to another and ions are formed.  Ions are atoms or groups of atoms with positive or negative charges.  They are formed by the addition or removal of electrons.  If an element has only 1 or 2 electrons in its furthest sub-shell (usually s) it tends to lose them easily.  If an element has an almost full furthest sub-shell (p sub-shell) it tends to gain electrons easily.

7. CATIONS AND ANIONS  Imagine the scales filled with protons on one side and electrons on the other  What would happen if we took an electron away?  What would happen if we added another electron?  Ions are atoms or groups of atoms with positive or negative charges.  They are formed by the addition or removal of electrons.  Positive ions are called CATIONS they form when an electron is.........  Negative ions are called ANIONS they form when an electron is.........  Metals are found on the left hand side of the periodic table, so they have a tendency to form............................ions  Non-metals are found on the right hand side of the periodic table, so they have a tendency to form...................................ions + -

8. Have a go at the electronic configuration of atoms and ions P11

9. BONDING  A filled outer sub-shell is stable.  Of the elements, only the noble gases have that arrangement.  The other atoms can achieve the same structure by combining together and rearranging their valence electrons.  The outcome is called a chemical bond – compounds form. It consists of a pair of electrons, usually from different atoms.  A chemical compound contains two or more different atoms joined together by chemical bonds. Why do chemicals bond together, when they are actually quite stable in their element form? – think of magnets!

10. THERE ARE TWO MAIN WAYS TO BOND!  1. transfer of electrons from one atom to another.  What are formed when this happens?  What do you think we call this type of bond?  2. Sharing of electrons between atoms  Because electrons are shared between the atoms, neither atom in the bond becomes negative or positively charged, so no ions here!  We can get grey areas between the two types of bonds.

11. IONIC BONDING  First ions form as the electrostatic attraction of one atom of an element pulls strongly at the electron of a neighbouring different element’s atom.  This leads to one atom being left overall positively charges – forming a cation  The other atom that has drawn the electron to it, is now overall negatively charged – forms an anion.

12. TABLE ON P1

13. CATIONS AND ANIONS  Positive ions formed most readily by groups 1 and 2  Na Na + + e -  Have a go at the others....  Negative ions formed most readily by groups 6 and 7  ½ Cl 2 + e - Cl - Why the ½ for chlorine? Remember to check the valency before assigning the ion charge!

14. FORMATION OF THE IONIC BOND....OPPOSITES ATTRACT!  Overall there is a transfer of electrons from the metal to the non-metal forming ions.  Oppositely charged ions attract each other.  Each positive ion attracts a negative ion.  Each negative ion attracts a positive ion.  Remember I said that sometimes we get discrete clusters of molecules, and in others we get giant structures.  An ionic crystal consists of an array of positively charged and negatively charged ions held together by electrostatic attraction.

15. DRAWING IONIC BONDING  Lewis dot structures... Named after an American chemist Gilbert Newton Lewis, developed between Bohr’s model of the atom and that of Schrodinger and Heisenberg.  Although we know the atom’s shells to have sub-levels we can’t draw them in when doing Lewis structures, so it’s simpler to stick to the Bohr model.  So we go back a step to these:  Our s and p levels are grouped

16. LET’S LOOK Copy the structure into your worksheet

17. THE GIANT CRYSTAL STRUCTURE OF SODIUM CHLORIDE  Each Na+ ion is surrounded by Cl- ions in 3 dimensions to form a giant crystal.  The bonding is ionic, ions held by electrostatic attraction, i.e positive attracting negative charges and visa versa.  These bonds are very strong and give the resulting structure high melting points. Ions represented as spheres ‘Ball and stick’ representation

18. PROPERTIES OF IONIC COMPOUNDS  When they dissolve in water or are heated until melted (molten) they conduct electricity because the ions are free to move around.  Because they are giant crystal structures they have lots of bonds, these take a lot of energy to break apart, so to go from solid to liquid requires a lot of heat. This means that their melting points are high.  They are usually soluble in water, this is because they contain ions and water can pull these apart....

19. HAVE A GO AT SOME MORE P5  Carry on and do the homework section...

20. BREAK!

21. RECALL ELEMENTS, COMPOUNDS AND MIXTURES Activity 1.Divide into 5 groups 2.Decide which of the text / pictures fits into each category. Activity 1.Divide into 5 groups 2.Decide which of the text / pictures fits into each category. ICT skills and Literacy

22. SEPARATING MIXTURES  Remember this isn’t breaking compounds – substances chemically bonded together.  Think back to iron and sulphur mix and iron sulphide...

23. SEPARATING MIXTURES  Remember this isn’t breaking compounds – substances chemically bonded together.  Think back to iron and sulphur mix and iron sulphide...  We can separate a liquid and a solid by filtration.  We can separate them too by centrifuging.  We can separate two liquids that are mixed together by distillation  We can separate two small volumes of liquids into their components by chromatograph

24. LEARNING OUTCOMES  Recall spdf configuration  Define how stability occurs when elements chemically combine and energy is lowered  Define the formation of ions  Predict the structure of ions  Show the bonding that occurs between ions in an ionic bond  Recall elements, compounds and mixtures  Be able to separate substance by their physical properties ? Rate your confidence in what you learnt today out of 10, and anything you are still unsure of...