Access to Science: Chemistry Starter: recall ionic bonding News! Reflective Learner

Learning aims:  Recall ionic bonding  Describe covalent bonding  Write the formulae of simple covalent compounds  Recall elements, compounds and mixtures  Be able to separate substance by their physical properties Literacy and Numeracy

This hold true until we start to fill up d block elements

 Exist as solids  Due to the size of the structures that they form they tend to have high melting and boiling points, as it takes lots of energy to break up the large crystals formed.  When they dissolve in water the ions are free so they will conduct electricity  They will also break apart from the giant structure when melted (molten) and exist as ions, these too will conduct electricity. Properties of ionic compounds

 Where are the non-metals on the periodic table?  When we look at group 4 these form a different sort of bond with other elements from other groups.  Likewise elements in groups 5,6 and 7 when forming bonds with themselves form a different sort of bond. Non-metal – non-metal bonds.

N 2, Cl 2, H 2 O The Octet rule of 8 outer electrons still applies here!

8 outer electrons in each atom! F F

 This is an attractive force between 2 or more non- metals  The atoms achieve filled outer shells by sharing outer electrons. Covalent worksheet!

 Attractive force between 2 nuclei  A shared pair of electrons The bond is held together by electrostatic attraction between the 2 nuclei and the bonding electron pair.

 Covalent bonding results in the formation of molecules. Larger structures do form but we will look at these later.  Unlike ionic bonding that forms giant structures of ions.  A molecule is defined as two or more atoms joined together by covalent bonds

1 shared pair of electrons forms a single bond Seen written as: Cl-Cl

2 shared pairs of electrons forms a double bond Seen written as: O=O

3 shared pairs of electrons forms a triple bond Seen written as: N=N

Break time!

Hydrogen – the first shell can only have 2 electrons remember HH 2 Hydrogen atoms through the formation of a covalent bond form a molecule of hydrogen sharing 1 pair of electrons Can be written as H-H or H 2 XX HH x

Try some out! Stretch & challenge Reflective Learner

 Sometimes an atom will donate two electrons (a pair) to another atom to form the covalent bond.  This is seen in a number of molecules a few examples are shown here: Dative covalent bonding coordinate bonds Both electrons come from sulphur There is a link on my site to give you further info

 Covalent bonds form from shared pairs of electrons  Atoms achieve a full outer shell  Shared electrons exist as a covalent bond  Covalent bonding is found between non-metals  Covalent bonds are strong within the molecules.  They don’t conduct electricity in any form because there are no charged ions.  They exist as solids, liquids or gases.  Simple covalent molecules have low melting and boiling temperatures because weak forces between sets of molecules are easily broken.  Some may be soluble in water, but often insoluble.  There are single, double and triple bonds Summary of covalent bonding P6

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. Reflective Learner Effective Participator Reflective Learner Effective Participator

 Remember this isn’t breaking compounds – substances chemically bonded together.  Think back to iron and sulphur mix and iron sulphide... Separating mixtures Team worker Independent enquiry Team worker Independent enquiry

 We can separate a liquid and a solid by filtration.  We can separate them too by centrifuging.  Next week we will see how we separate liquids:  We can separate two liquids that are mixed together by distillation  We can separate two small volumes of liquids into their components by chromatograph Separating mixtures

 Recall ionic bonding  Describe covalent bonding  Write the formulae of simple covalent compounds  Recall elements, compounds and mixtures  Be able to separate substance by their physical properties Learning outcomes ? Rate your confidence in what you learnt today out of 10, and anything you are still unsure of...