3,2,1! 3 Minutes Start Timer Connect your learning List……. 3 covalent molecules 2 differences between ionic and covalent bonds 1 Giant covalent lattice

Learning outcomes Define covalent bonding and give examples of molecules that form covalent bonds (E) Draw dot and cross diagrams to represent single and multiple covalent bonds (D/C) State the meaning of “lone pairs” and represent them in dot and cross diagrams of covalent bonds(B)

Covalent Bonds Non metals only A bond formed by a shared pair of electrons An electron pair occupies the space between two atoms’ nuclei The negatively charged electrons are attracted to the positive charges of both nuclei This attraction overcomes the repulsion between the two positively charged nuclei

Positive charge (nucleus) I negative charge (pair of electrons) I Positive charge (nucleus) The resulting attraction is the covalent bond that holds the two atoms together.

Short hand notation for a covalent bond is a line – e.g. H-H A covalent bond is directional i.e. it just acts between the two atoms involved in the bond. Ionic bonds act in all directions Many covalent molecules are termed ‘simple molecules’ Can you draw the covalent bonding in water, ammonia and methane?

Single covalent bonds For each of these examples draw out the dot and cross diagram and write down the short hand of the covalent bond Eg hydrogen chloride molecule (H-Cl) 1. Hydrogen molecule 2. Chlorine molecule 3. Water molecule 4. Methane Molecule 5. Ammonia Molecule

Single Covalent molecules check your answers

Lone pairs Sounds like an oxymoron... How can something be lone and a pair! Sometimes pairs of electrons are not used for bonding e.g. in ammonia there is one lone pair and water, there are two lone pairs. Circle the lone pairs in a different colour on your diagrams and write the definition of a lone pair (see pg 55 of your text book for a hint!). A lone pair gives a concentrated region of negative charge. We will be looking at how lone pairs can affect the chemistry of a molecule in the next few lessons.

Multiple covalent bonds More commonly referred to as double and triple bonds! Some non-metallic elements can share more than one pair of electrons Sharing 2 pairs of electrons = double bond Sharing 3 pairs of electrons = triple bond Can you draw dot and cross diagrams for oxygen, nitrogen and carbon dioxide?

Check your answers Make sure you label whether they have a double or triple bond!

Complete questions 1 and 2 on page 55 of your text book.

Homework Complete the exam questions and bring your answers to the next lesson for review