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Chemical Bonding

Learn about chemical bonding and the properties of elements in this comprehensive guide. Explore ionic and covalent bonding, electron configurations, and more.

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Chemical Bonding

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  1. Chemical Bonding

  2. Elements are the simplest substances. There are about 100 different elements S Fe N O C K N N N N N N N N Elements • Each elements has just one particular type of atom that is different to the atoms in any other element • Even in elements atoms usually join (bond) together. • In some elements atoms bond to form small simple structures. • In other elements atoms bond into giant structures with millions of atoms.

  3. Reacting is different to just mixing. The physical and chemical properties of compounds are very different to their original elements. ELEMENTS COMPOUND O C O O O (colourless gas, that supports combustion) (black solid) (a colourless gas, that extinguishes fire) Compounds are not just mixtures Carbon dioxide Carbon + oxygen C

  4. Activity Copy the Table and fill in the last column. Rust consists of iron combined with oxygen Name Formula Element or compound Sodium chloride NaCl compound Nickel Ni element Copper sulphate CuSO4 compound Water H2O compound Oxygen O2 element Rust Fe2O3 compound Mercury Hg element Sand SiO2 compound

  5. Two of the three particles in atoms have an electrical charge. Protons +1 Neutrons 0 Electrons -1 19 F 9 20 Ne 10 Fluorine 9 protons 9+ 9 electrons 9- 10 neutrons 0 Total Charge 0 Neon Copy & Fill in the gaps ___ protons ___ ___ electrons ___ ___neutrons ___ Total Charge ___ No charge on element atoms BUT atoms have equal numbers of protons and electrons. This means their overall charge = zero. For example 10+ 10 10 10- 0 10 0

  6. The electrons around the outside of atoms are arranged in layers called shells 1st Shell: 2 electrons 2nd Shell: 8 electrons 3rd Shell: 8 electrons Noble Gases: full shells Each shell has a maximum number of electrons that it can hold. In noble gases the shells are completely full rather than partially full. During bonding other atoms try to attain the “full electron shell” structure of the noble gases.

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

  8. Ionic Bonding Involves the gain or loss of electrons to form charged atoms called ions. The positive ions and negative ions are attracted to each other and bond together.

  9. IONIC BONDING

  10. Most ionic compounds contain a metal and a non-metal. n+ Lose 1 or more electrons (negative) Neutral atom Positive ion n- Gain 1 or more electrons Neutral atom Negative ion IONIC BONDING When metals react they lose outer shell electrons to leave a full electron shell. This produces a charged atom (ion) with a + charge. When non-metals react with a metal they gain electrons to achieve a full electron shell.

  11. The oppositely charged ions are attracted into a lattice that gets bigger and bigger until it consists of millions of ions + + + + + - - - - + + + opposites attract + - - - + + + + + + - - - - - - - - + - + Opposites attract – lattices And ion, and ion, and ion!

  12. Metals lose electrons to form positive(+) ions called cations. n+ n- Ions and electron structures Non-metals gain electrons to form negative (–) ions called anions. • We know that the atoms lose or gain electrons to achieve full electron shells.

  13. Sodium has 1 electron in its outer shell. Loses 1 electron Na+ Na Formation of sodium chloride1. Formation of sodium ions If it loses this it will have no partially filled shells. Sodium atom (2.8.1) Sodium 1+ ion (2.8.0) This only happens if there is another atom able to accommodate the lost electron.

  14. Chlorine has 7 electrons in its outer shell. Cl Gains1 electron (from sodium) Cl Formation of sodium chloride 2.Formation of Chloride ions If it gains 1 electron it can achieve a full outer electron shell. It is, therefore, going to be able to accept the electron that the sodium wants to lose. Chlorine atom (2.8.7) Chlorine I - ion (2.8.8)

  15. Sodium loses its outer electron. Chlorine gains it. The result is both end up with full shells Cl Na Formation of Sodium Chloride- the overall process. Cl Na Two oppositely charged ions are formed, which attract. Millions of such pairs form a giant lattice

  16. We can assume full inner electron shells. We can therefore sometimes shorten bonding diagrams by omitting to draw the inner electron shells. Na Cl Cl Na Simpler electron diagrams

  17. More than one electron may be transferred between atoms in ionic bonding. O O2- Mg Magnesium Oxide 2.6 2.8.2. Magnesium atom Oxygen atom Mg2+ 2.8 2.8 Bonding in Magnesium Oxide

  18. Draw a simplified bonding diagram (omitting inner shells) for magnesium oxide. Mg O Magnesium Oxide Magnesium atom Oxygen atom O2- Mg2+

  19. Copy the diagram and draw another box showing the electron configuration in sodium fluoride. Na F Sodium Fluoride 2.7 2.8.1. Sodium atom Fluorineatom Na+ F- 2.8 2.8

  20. In aluminium fluoride it is the non-metal atoms that we need more of. F F F F F F Al Al Bonding in Aluminium Fluoride

  21. Following the previously shown slides draw bonding diagrams for the compounds formed from the following atoms: Lithium (2.1) and fluorine (2.7) Sodium (2.8.1) and sulphur (2.8.6) Magnesium (2.8.2) and sulphur (2.8.6) Magnesium (2.8.2) and fluorine (2.7) Aluminium (2.8.3) and nitrogen (2.5) Activity Remember that the total number of electrons lost by the metal must equal the total number of electrons gained by the non-metal

  22. Both sodium chloride and magnesium oxide are simple ionic compounds. In both cases the metal and non-metal need to lose or gain the same number of electrons respectively. Na Cl Cl- Na+ 1 electron O2- Mg2+ O Mg 2 electrons Electrons Lost = Electrons Gained This is not always the case.

  23. Consider the reaction of sodium with oxygen. Sodium (2.8.1) needs to lose 1 electron. Oxygen (2.6) needs to gain 2 electrons This can only happen if there are two sodium ions formed for every one oxygen ion formed. Na+ Na O O2- 1 electron per sodium Na+ Na Different numbers of electrons The formula will be Na2O.

  24. Consider the reaction of magnesium with chlorine. Magnesium (2.8.2) needs to lose 2 electron. Chlorine (2.8.7) needs to gain 1 electrons We need 2 chlorines for every one magnesium. Cl Cl- Mg Mg2+ Cl- Cl 2 electrons Different numbers of electrons The formula will be MgCl2

  25. When atoms form ions they aim to attain electron shells that are either completely full or completely empty. If we know the electron configuration of an atom we can usually work out how many electrons it must lose or gain to achieve a noble gas configuration. This will tell us the charge on its ion. Charges on ions

  26. Octet Rule: atoms will bond with other atoms to gain, lose or share electrons in order to achieve a full outer shell (i.e. 8) • Ion = charged atom • Ionic bond: is formed between positive ions and negative ions which are attracted to each other and bond together. • Most ionic compounds contain a metal and a non-metal. • Need to know MgO and NaCl

  27. COVALENT BONDING

  28. Covalent Bonding Involves the sharing of electrons between atoms to form molecules

  29. Covalent compounds are generally formed when non-metal atoms react together. Sharing of electrons Covalent compounds

  30. Covalent compounds are held together by this sharing of electrons. A covalent bond is when a pair of electrons are shared It is sometimes represented in full bonding diagrams (see figure 1). Often these bonds are just shown as a pair of electrons (xx) or even just a line (see figure 2). - Figure 1 Figure 2 F F X X F F Covalent bonds

  31. Sometimes just a few atoms join together in this way. . covalent bonds Small covalent structures

  32. H H Cl H C Cl Cl N H H H H H Covalent bonding and electron structures

  33. 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

  34. Both fluorine and chlorine needs 1 more electron to attain a full electron shell. Cl Cl F F (2,7) (2,8,7) (2,8) (2,8,8) Copy this diagram and add the electron arrangements that could exist in fluorine chloride (FCl).

  35. 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

  36. Hydrogen (1) needs 1 more electron but oxygen (2.6) needs 2 more. Therefore, we need 2 hydrogens. O O H H H H H H O Covalent bonding in water

  37. 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 hydrogens per 1 nitrogen? • Draw bonding diagrams for ammonia.

  38. 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? • Draw bonding diagrams for methane.

  39. Oxygen (2.8.6) needs 2 more electrons to attain a full electron shell. O O O O Covalent bonding in oxygen O=O 4 electrons

  40. Nitrogen (2.8.5) needs 3 more electrons to attain a full electron shell and forms a triple bond. Draw a bonding diagram of nitrogen. N=N N N N N 6 electrons

  41. Hydrogen fluoride (HF) Hydrogen sulphide (H2S) Ethane (C2H6 and the carbons are joined by a single covalent bond) Carbon dioxide (CO2 and the carbon oxygen bonds are double bonds) Draw ‘dot and cross’ type bonding diagrams for each of the following: Bohr Models H H F H O C O C C H H S H H H H

  42. One form of carbon is diamond. Each diamond consists of millions of carbon atoms bonded into a single giant structure. It is very hard. Diamond strong covalent bonds carbon atoms Giant covalent structures: diamond

  43. BONDING AND PHYSICAL PROPERTIES

  44. These are things such as: Density Conductivity Malleability/ brittleness Melting point Bonding and physical properties The type of structure that substances have has a huge effect upon physical properties. The next few slides illustrate just a few of the general patterns.

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