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Chapter 7

Chapter 7. Keefe 1415. Valence electrons. These are the electrons that are available to participate in reactions: they are always in the OUTSIDE shell of electrons The number of valence electrons determines the chemical properties of the element. Valence Electrons.

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Chapter 7

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  1. Chapter 7 Keefe 1415

  2. Valence electrons • These are the electrons that are available to participate in reactions: they are always in the OUTSIDE shell of electrons • The number of valence electrons determines the chemical properties of the element

  3. Valence Electrons • Lithium and sodium each have 1 outer electron, so they have similar properties. For example, they are soft metals and they corrode easily in air.

  4. Valence Electrons • In forming compounds, atoms tend to achieve the electron configuration of a noble gas • Octet- a set of 8 valence electrons

  5. Valence electrons • Exceptions to the OCTET RULE include H, He, and B: • H and He are happy with just TWO electrons • B is happy with SIX electrons

  6. Valence Electrons • Atoms of metals tend to LOSE all of their valence electrons to leave a complete octet in the next-lower energy level • Atoms of nonmetals tend to GAIN electrons or SHARE electrons with another nonmetal to achieve an octet

  7. Valence electrons

  8. Anions Versus Cations

  9. Anions versus Cations • Cationswant to LOSE electron(s) and therefore have a net POSITIVE charge:

  10. Anions Versus Cations • Name of a cation is the same as the element name, then add the word ‘ion’: ion

  11. Anions Versus Cations • Some transition metals have multiple possible oxidation states (charges). To name them, you add a ROMAN NUMERAL after the name of the element to indicate the charge: ion

  12. Anions versus Cations • Anions want to GAIN electron(s) and therefore have a NEGATIVE charge

  13. Anions Versus Cations • Name of an anion is usually the name of the element, BUT drop the last syllable and add ‘ide’: • Clorine atoms form chloride anions • Oxygen atoms for oxide anions

  14. Lewis dot structures of atoms • Simply put the symbol of the element and add dots around it until you have represented all the valence electrons:

  15. Valence Electrons

  16. Compound: • any substance made up of two or more elements.

  17. Binary Compounds “Binary” means “two”, as in there are two different elements involved. • There are two types: • Ionic • Covalent

  18. Ionic Compounds • Ionic Compounds are made from a Metal and a Non-metal.

  19. Ionic Compounds • Naming:metal cationfirst, then non-metal anion with –ide at the end. • Example: NaCl: Sodium Chloride • In this Ionic Compound, there is one Sodium atom for every Chlorine atom.

  20. Balancing Ionic Compounds • Sometimes an Ionic Compound will have little numbers included in its formula: • Ex. Magnesium Chloride = MgCl2

  21. Balancing Ionic Compounds • These numbers are called subscripts, and they tell you how many of the previous atoms you have. • Onemagnesium, twochlorines • Magnesium Chloride = MgCl2

  22. Balancing Ionic Compounds • Beryllium Fluoride: how do you know whether or not subscripts are needed?

  23. Balancing Ionic Compounds • There is nothing in their namethat indicates that numbers are necessary in the formula • You need the: • Oxidation Number (we call it the charge)

  24. Balancing Oxidation State Numbers • We’re trying to get these two numbers to add up to zero: • Be2+ and F- • BeF2 = Beryllium Fluoride

  25. A visual representation Be2+ F- We need two “minus ones” to balance out “plus two”

  26. Another Trick: • How about Aluminum Oxide? • First, find their oxidation numbers: • Al3+ and O-2 • How can we balance out a 3+ and a -2? • Trick: Swap the numbers! • Al2O3 = Aluminum Oxide

  27. Writing a Formula Write the formula for the ionic compound that will form between Ba2+ and Cl. Solution: 1. Balance charge with + and – ions 2. Write the positive ion of metal first, and the negative ion Ba2+ClCl 3. Write the number of ions needed as subscriptsBaCl2

  28. Learning Check Write the correct formula for the compounds containing the following ions: 1. Na+, S2- 2. Al3+, Cl- 3. Mg2+, N3-

  29. Solution 1. Na+, S2- Na2S 2. Al3+, Cl- AlCl3 3. Mg2+, N3- Mg3N2

  30. Naming Compounds Binary Ionic Compounds: • 1. Cation first, then anion • 2. Monatomic cation = name of the element • Ca2+ = calcium ion • 3. Monatomic anion = root + -ide • Cl- = chloride • CaCl2 = calcium chloride

  31. Naming Binary Ionic Compounds • Examples: NaCl ZnI2 Al2O3 sodium chloride zinc iodide aluminum oxide

  32. Learning Check Complete the names of the following binary compounds: Na3N sodium ________________ KBr potassium ________________ Al2O3 aluminum ________________ MgS _________________________

  33. Solution Complete the names of the following binary compounds: Na3N KBr Al2O3 MgS sodium nitride potassium bromide aluminum oxide magnesium sulfide

  34. Transition Metals Elements that can have more than one possible charge MUST have a Roman Numeral to indicate the charge on the individual ion. 1+ or 2+ 2+ or 3+ Cu+,Cu2+ Fe2+, Fe3+ copper(I) ion iron(II) ion copper (II) ion iron(III) ion

  35. Names of Variable Transition Ions These elements REQUIRE Roman Numerals because they can have more than one possible charge: anything except Group 1A, 2A, Ag, Zn, Cd, and Al

  36. Names of Variable Ions Or another way to say it is: Transition metals and the metalsin groups 4A and 5A (except Ag, Zn, Cd, and Al) require a Roman Numeral. FeCl3(Fe3+) iron (III) chloride CuCl(Cu+ ) copper (I) chloride SnF4 (Sn4+) tin (IV) fluoride PbCl2 (Pb2+) lead (II) chloride Fe2S3 (Fe3+) iron (III) sulfide

  37. Examples of Older Names of Cations formed from Transition Metals(you do not have to memorize these)

  38. Learning Check Complete the names of the following binary compounds with variable metal ions: FeBr2 iron (_____) bromide CuCl copper (_____) chloride SnO2 ___(_____ ) ______________ Fe2O3 ________________________ Hg2S ________________________

  39. Solution Complete the names of the following binary compounds with variable metal ions: iron ( II ) bromide copper ( I ) chloride tin (IV) oxide iron (III) oxide mercury (I) sulfide FeBr2 CuCl SnO2 Fe2O3 Hg2S

  40. Polyatomic ions: MEMORIZE (and I have a trick to help)

  41. Naming polyatomic ions YAS THERE ARE MOAR “ate” anions have one more oxygen then the “ite” ion, but the same charge. If you memorize the “ate” ions, then you should be able to derive the formula for the “ite” ion and vice-versa: • Examples: • sulfate is SO42- , so sulfite has the same charge but one less oxygen (SO32-) • nitrate is NO3-, so nitrite has the same charge but one less oxygen (NO2-)

  42. Naming Polyatomics • A sulfate ion is SO42- . To get the formula for hydrogen sulfate ion, you add a hydrogen ion to the front of the formula. Since a hydrogen ion has a 1+ charge, the net charge on the new ion is less negative by one.

  43. Naming polyatomics • Add one more hydrogen to the mix and you get:

  44. Naming polyatomics • Similarly, adding/subtracting oxygens results in:

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