To know that different elements join together * To know that different elements join together ** To recognise different types of bonding by their properties *** To explain why they have those properties

Reminder

Close up atoms

Closer still… 24 12 Mg electron - 12 proton + neutron

How many protons, electrons and neutrons does fluorine have? 19 9 F Atomic weight Number of protons AND neutrons Atomic number Number of protons (Number of electrons too) electron - Proton + Neutron 9 9 10

How does this look? 19 9 F electron - 9 Proton + Neutron 10

Only electrons go in shells How do the shells work? Shells Only electrons go in shells

We number shells from the middle 1 This will be shell 2 This will be shell 3 This will be shell

F Shell 1 will hold 2 electrons Shell 2 will hold 8 Shell 3 will hold 19 9 F Shell 1 has electrons Shell 2 has Shell 3 has 2 7 This is fluorine. It has electrons. 9 * Once you get past element 20 things get a little more complicated!

P Shell 1 will hold 2 electrons Shell 2 will hold 8 Shell 3 will hold Shell 1 has electrons Shell 2 has Shell 3 has 2 31 15 P 8 5 This is phosphorus. It has electrons. 15 * Once you get past element 20 things get a little more complicated!

Ca Shell 1 will hold 2 electrons Shell 2 will hold 8 Shell 3 will hold Shell 1 has electrons Shell 2 has Shell 3 has Shell 4 has 2 40 20 Ca 8 8 2 This is calcium. It has electrons. 20 * Once you get past element 20 things get a little more complicated!

Chemical Bonds

Starter What needs to happen to Sodium to help it reach its most stable state?

Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons C would like to N would like to O would like to Gain 4 electrons Gain 3 electrons Gain 2 electrons

Name of chemical Sucrose Sodium chloride Ethanol Copper sulphate State at room temperature?   Melting point low or high? Does it dissolve in water Does it conduct electricity as a solid? Does it conduct electricity in aqueous solution

Types of bond

IONIC BOND bond formed between two ions by the transfer of electrons

Formation of Ions from Metals Ionic compounds result when metals react with nonmetals Metals lose electrons

Ions from Nonmetal Ions In ionic compounds, nonmetals in 5, 6, and 7 gain electrons from metals

F K In an IONIC bond, electrons are lost or gained, resulting in the formation of IONS in ionic compounds. F K

K F

K F

K F

K F

K F

K F

+ _ K F

K F _ + The compound potassium fluoride consists of potassium (K+) ions and fluoride (F-) ions

K F _ + The ionic bond is the attraction between the positive K+ ion and the negative F- ion

Properties of ionic bonds Bond formed by transfer of electrons Produce charged ions in all states. Will conduct electricity when dissolved Will conduct electricity when melted Have high melting point. Examples; NaCl, CaCl2, K2O

So what are covalent bonds?

In covalent bonding, atoms still want to achieve a full outer shell But rather than losing or gaining electrons, atoms now share electrons

Cl2 Chlorine forms a covalent bond with itself

How will two chlorine atoms react? Cl Cl

Cl Cl Each chlorine atom wants to gain one electron to achieve a full shell of 8 electrons

Cl Cl

Cl Cl

Cl Cl

Cl Cl

Cl Cl Full shell

Cl Cl Full shell

COVALENT BOND bond formed by the sharing of electrons

SHARE COMPLETE NONMETALS What is a covalent bond? Atoms ___________ one or more electrons with each other to form the bond. Each atom is left with a ________________ outer shell. A covalent bond forms between two _________________. Example 1: Hydrogen + Hydrogen Example 2: Hydrogen + Oxygen SHARE COMPLETE NONMETALS

Covalent Bond Between nonmetallic elements Formed by sharing electron pairs They are not conductors at any state They typically have low boiling and melting points Examples; O2, CO2, C2H6, H2O

Now try the covalent bonding practice sheet

  Ionic bonds Covalent bonds Melting and boiling points – high or low? Would they conduct electricity when melted (liquid)? Would you expect them to conduct electricity when dissolved in water? Do they conduct electricity as a solid What sort of chemicals would you expect to fall into this group?

Covalent or ionic compound? Using the information from your experiments decide for each chemical if it has ionic or covalent bonds (you might need to check back on the information you have already). Does this fit with the facts you know already about ionic and covalent bonds? Yes/no Explain why you would expect the chemicals you were given to have the properties they do. Covalent or ionic compound?