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Review of Chemical Bonding

Review of Chemical Bonding. Metal and non-metal. Non-metals only. Metals only. Types of bonding. Atoms can be joined together in 3 possible ways. Ionic Bonding. Covalent Bonding. Metallic Bonding.

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Review of Chemical Bonding

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  1. Review of Chemical Bonding

  2. Metal and non-metal Non-metals only Metals only Types of bonding Atoms can be joined together in 3 possible ways Ionic Bonding Covalent Bonding Metallic Bonding All three types involve changes in the electrons in the outermost electron shells of the atoms

  3. Covalent compounds are formed when NON-METAL atoms react together. Covalent bonding – bonding in which a pair of electrons, one from each atom, is shared between two atoms. Covalent compounds

  4. Covalent compounds are held together by this sharing of electrons. A pair of electrons shared in this way is known as a covalent bond. It is sometimes represented in full bonding diagrams (see figure 1). Often these bonds are just shown as a line (see figure 2). - Figure 1 Figure 2 H O Covalent bonds - H

  5. Sometimes just a few atoms join together in this way. This produces small covalent molecules – often known as simple molecular structures. a simple molecular structure covalent bonds Small covalent structures

  6. Covalent compounds are insoluble in water unlike ionic Covalent compounds don’t conduct electricity in water There are no ions in covalent compounds, unlike ionic compounds. Covalent compounds generally have much lower melting and boiling points than ionic. Covalent compounds form distinct molecules Interact with each other through ‘weak’ INTERMOLECULAR FORCES Bonding and physical properties electrons fixed in covalent bonds H O H

  7. Sometimes millions of atoms are joined together by covalent bonds. This produces a rigid 3-D network called a giant lattice. a giant lattice covalent bonds Giant covalent structures

  8. Properties of small covalent molecules is different from that of giant covalent structures. Carbon in the form of graphite Exists in layers held together by weak intermolecular forces Will not dissolve in solvents High mpt and bpt Electrons from the shared bond can move freely through each layer, so graphite is a conductor. Carbon in the form of diamond High mpt and bpt Hard, will not dissolve Strong 3D network Giant covalent structures

  9. Generally substances with giant structures have high melting points and boiling points. Small molecules have melting points and boiling points that increase as the size of the molecule increases. Bonding and physical properties In giant structures all the atoms are tightly bonded together. Usually they are high melting-point solids. + + - - Small molecules tend to be gas, liquid solids with low melting points. - - + + + + - - - + - weak forces between molecules + + - - + + + - + - + -

  10. The driving force for covalent bonding is the attainment of outer electron shells that are completely full. This is achieved by sharing electrons where the shared electrons count towards the outer shells of both atoms. H H H H O C C Cl Cl N O H H H H H Covalent bonding and electron structures Water O Chlorine Carbon dioxide Methane Ammonia

  11. Chlorine (2,8,7) needs 1 more electron to attain a full electron shell. Cl Cl Cl (2,8,7) (2,8,7) Cl (2,8,8) (2,8,8) Covalent bonding in chlorine Cl-Cl

  12. Both hydrogen (1) and chlorine (2,8,7) needs 1 more electron to attain a full outer shell. Cl Cl H (1) (2,8,7) H (2) (2,8,8) Covalent bonding in hydrogen chloride H-Cl

  13. Hydrogen (1) needs 1 more electron but oxygen (2,6) needs 2 more. Therefore, we need 2 hydrogen's. O O H H H H H H O Covalent bonding in water

  14. Hydrogen (1) needs 1 more electron. H H H H H H H H C C 4 • How many does carbon (2,4) need? 4 • How many hydrogens per 1 carbon?

  15. Hydrogen (1) needs 1 more electron. H H H H H H N N 3 • How many does nitrogen (2,5) need? 3 • How many hydrogen's per 1 nitrogen? C3C4

  16. Mostly electrons are shared as pairs. There are some compounds where they are shared in fours or even sixes. This gives rise to single, double and triple covalent bonds. Again, each pair of electrons is often represented by a single line when doing simple diagrams of molecules. Cl-Cl O=O N=N Double bond Triple bond Single bond Covalent bonding - multiple bonds

  17. Oxygen (2,8,6) needs 2 more electrons to attain a full electron shell. Covalent bonding in oxygen O=O 4 electrons O O O O X X X X X X X X X X X X

  18. Activity Spider Diagram Create a spider diagram of all the things you know about Covalent bonding using your own book and a textbook.

  19. STARTER • What do you already know about atoms and the periodic table? • Questionnaire

  20. Group 1 - Alkali Metals Learning Objective – To further our knowledge of the group 1 elements.

  21. Group 1 - Alkali Metals • All: Explain that alkali metals are stored under oil because they react with air and water. • Most: Describe the reaction of lithium, sodium and potassium with water. • Some: State the balanced symbol equation for the reaction of an alkali metal with water.

  22. These are the alkali metals or Group 1 Elements. Li Na K Rb Cs H He Fr Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Rf Db Sg Bh Hs Mt ? ? ? Alkali metals and the Periodic Table

  23. Group 1 - Alkali Metals • In your groups you have got five minutes to write down everything you know about your given element. • After 5 minutes swap with the group on your right and add to the information that the group has already written about that element.

  24. When these atoms react each loses the one electron in its outer shell to for a positive ion.The loss of electrons is called OXIDATION 2,1 2,8,1 2,8,8,1 Electronic Structure Li Lithium Na Sodium K Potassium Rb Rubidium Cs Caesium

  25. The atoms in the Group 1 elements are bonded together using just one outer shell electron per atom. As a result, melting points are low compared to most metals. Melting Points 63 29 Can you predict the missing data?

  26. Reactivity increases down the group. Reactions all involve the loss of the outermost electron which changes the metal atom into a metal 1+ ion. Losing this electron seems to get easier as we go down the group. Li Na K Rb Cs Trends in Chemical Reactivity Reactivity Increases

  27. 1. The outer electron (-) gets further from the nucleus (+) as you go down the group. This reduces the force of attraction. 2. The inner shells ‘shield’ the outermost electron from the attraction from the nucleus. Both factors make it easier to lose the outer electron as you go down the group. Reactivity and Electron Structures Reactivity Increases

  28. Reactivity and Electron Structures

  29. Lithium fizzes quickly in water forming lithium hydroxide and hydrogen. Reaction of Lithium with Water Lithium + water  Lithium hydroxide + hydrogen 2Li(s) + 2H2O(l)  2LiOH(aq) + H2(g) The solution that remains is strongly alkaline.

  30. Sodium fizzes very quickly in water. The gas given off can be ignited by a lighted splint. Write a balanced equation for the reaction of sodium with water. sodium on water enlarged Reaction of Sodium with Water Sodium + water  Sodium hydroxide + hydrogen 2Na(s) + 2H2O(l)  2NaOH(aq) + H2(g)

  31. Lithium fizzes. Sodium reacts more vigorously. What will potassium do? Potassium + water Potassium + water  Potassium with Water Demo What will the word equation and chemical equations be for the reaction of potassium with water? Potassium hydroxide + hydrogen 2KOH(aq) + H2(g) 2K(s) + 2H2O(l) 

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