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REGENTS REVIEW,JUNE 9, 10 CAIAFA-MAY

CHEM IS FUN. REGENTS REVIEW,JUNE 9, 10 CAIAFA-MAY. DRAW THE DOT STRUCTURES OF H 2 ,O 2 ,N 2 ,Cl 2 ,Br 2 ,I 2, F 2 .    1) How would you estimate the relative melting and boiling points of these?    2) Put them in ascending boiling point order and indicate how you do this.

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REGENTS REVIEW,JUNE 9, 10 CAIAFA-MAY

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  1. CHEM IS FUN REGENTS REVIEW,JUNE 9, 10 CAIAFA-MAY DRAW THE DOT STRUCTURES OF H2,O2,N2,Cl2,Br2,I2,F2 .    1)How would you estimate the relative melting and boiling points of these?    2)Put them in ascending boiling point order and indicate how you do this.     3)Indicate the type of molecule and type of bond.    4)List the characteristics and explain them with the bonding and type of attraction. THIS H SHARES THE 2 ELECTRONS IT NEEDS, IT NOW HAS THE CONFIGURATIONOF He: THIS H SHARES THE 2 ELECTRONS IT NEEDS, H IS NOT AN OCTET ELEMENT D. STEP 1 H2 H H H H STEP 2 H H = THE IONIC CHARACTER IS 0.0, THE BOND IS NON-POLAR COVALENT DRAW LEWIS VALENCE DOT STRUCTURE, CONNECT ONLY SINGLE ELECTRONS DRAW LEWIS VALENCE DOT STRUCTURE, EACH ELECTRON PAIR IS A DASH-LINE! DRAW LEWIS VALENCE DOT STRUCTURE, EACH SINGLE BOND IS 2 e-

  2. VSEPR (valence shell electron pair repulsion) • Gives geometry to assess polarity etc. • Assume central atom is LEAST electronegative. • Hydrogen cannot be the central atom as it makes only one bond.

  3. D. O2 Ne STEP 1 O O STEP 2 O O O O EACH O SHARES THE 4 e-(DOUBLE BOND) ELECTRONS IT NEEDS, IT NOW HAS THE OCTET CONFIGURATION OF NEON DRAW LEWIS VALENCE DOT STRUCTURE, CONNECT ONLY SINGLE ELECTRONS, 2 FOR EACH OXYGEN • Important: ALL OF THIS SERIES (H2,O2,N2,Cl2,Br2,I2,F2 ) ARE NON POLAR FOR THE FOLLOWING REASONS: • THEY HAVE IONIC CHARACTER OF 0.0 • THEY ARE LINEAR (SYMMETRICAL) – ONE BOND • THE BONDS ARE NON POLAR. • ALL (EXCEPT I AND Br) ARE GASSES AT STP. • ALL ARE ELEMENTAL MOLECULAES, OXIDATION STATE 0!

  4. Each nitrogen has an octet, isoelectronic to N N N Ne N STEP 1 STEP 2 N N The electron configuration of nonmetals will resemble the noble gas of their own period Connect only single electrons for covalent (molecular) substances. Each nitrogen shares 6 electrons, triple bond. RELATIVE ASCENDING BOILING AND MELTING SERIES H2(2g/mol), O2(32), N2(28), Cl2(70), Br2(161), I2(254), F2(38) H2(2g/mol), N2(28), O2(32), F2(38), Cl2(70), Br2(161), I2(254) Solid at STP Liquid at STP 1-LOWEST 2 3 4 5 6 7-HIGHEST Van der Waals increase with molar mass (gfm), use gfm for nonpolar

  5. DRAW THE DOT STRUCTURES FOR H2O, H2S, SiO2, CO2, CCl3F, CH4, HF. a.     -WHICH AR POLAR, WHICH ARE NOT. b.     -INDICATE THE TYPE OF BOND AND THE TYPE OF MOLECULE FOR EACH. c.      -PUT IN ASCENDING BOILING POINTS, INDICATE HOW YOU SO THIS. d.     -List the characteristics of each and explain why. H H O O shares the 8 e-achieve Neconfiguration Ne IONIC CHARACTER = 2.1 – 3.5 = 1.4 , POLAR COV. H H H O H O STEP 2 STEP 1 Next slide Connect single electrons Each H shares the 2 e-achieve He: configuration

  6. H O H YELLOW ARROWS ARE BOND POLARITY VECTORS, PONT TO MOST ELECTRONEGATIVE ELEMENT, NEGATIVE POLE. THE LEAST ELECTRONEGATIVE ATOM IS THE POSITIVE POLE AND GETS THIS POSITIVE POLE SYMBOL THE MOST ELECTRONEGATIVE ATOM IS THE NEGATIVE POLE AND GETE THIS NEGATIVE POLE SYMBOL WITH 2 BONDS AND 2 UNSHARED PAIRS OF e-, THE GEOMETRY IS BENT. H H THE BONDING IS CORRECT, BUT THE GEOMETRY IS NOT! O + + H H + O THE 2 YELLOW VECTOR ARROWS ADD UP TO THIS BIG ONE, WHICH REPRESENTS MOLECULAR POLARITY, POINTS TO NEGATIVE POLE. - -

  7. IONIC CHARACTER(EACH BOND) =| 2.1 – 2.6| = 0.5 , WEAKLY POLAR COVALENT. + = - - + + + + H H H H O S MOLECULAR POLARITY INCREASES (IF ASSYMETRICAL) AS IONIC CHARACTER INCREASES BOND POLARITY INCREASES causes causes WATER IS MORE POLAR HAS HIGHER MELTING AND BOILING POINTS H2O HAS GREATER IONIC CARACTER THAN H2S H2O HAS GREATER BOND POLARITY THAN H2S causes causes

  8. Si Si SI Note: THE Si IS HYBRID, NOT GROUND STATE. EACH THE Si HAS SHARED 4 e- TO ACHIEVE AN OCTET O STEP 1 O Si O O EACH OXYGEN HAS SHARED 4 e- TO ACHIEVE AN OCTET IONIC CHARACTER = |3.5 – 1.9| = 1.6, STRONGLY POLAR COV. STEP 2 O Si O SiO2 (silicon dioxide) is NONPOLAR , it is LINEAR ( 2 bonds) and symmetrical. The BONDS ARE polar but the molecule is not! NOTICE THE VECTOR ARROWS CANCEL = 0

  9. IONIC CHARACTER(EACH BOND) =| 2.1 – 2.6| = 0.5 , WEAKLY POLAR COV. C Note: THE C IS HYBRID, NOT GROUND STATE. + + - + O C O CO2 (carbon dioxide) is NONPOLAR , it is LINEAR ( 2 bonds) and symmetrical. The BONDS ARE polar but the molecule is not! = 0.0 NOTICE THE VECTOR ARROWS CANCEL H H H C F H C H H H POLAR BONDS,SYMMETRICAL NON POLAR MOLLECULE POLAR BONDS, A-SYMMETRICAL POLAR MOLLECULE

  10. IONIC CHARACTER = |1.3 – 3.2| = 1.9 , IONIC Note: Mg+ 2 has a Ne electron configuration. Mg + Cl Mg +2 STEP 1 - [ [ Cl The electron configuration of metals will resemble the noble gas of the period before the period of the metal Cl - [ [ Cl Mg IS AN ACTIVE METAL THAT NEEDS TO LOSE 2 e- Cl IS AN ACTIVE NON-METAL THAT NEEDS TO GAIN 1 e- Note: Cl- has a Ne electron configuration. MgCl2 Mg2+ Cl1-

  11. Al3+ F1- AlF3 • CHARACTERISTICS OF IONIC SOLIDS • Form crystal lattice solid with very strong electrostatic attractions between ions. • Ions are fixed in place, rendering the crystal non-conductive, brittle and hard. • The electrons cannot leave the ions, cannot conduct. • The strong electrostatic attractions make it difficult to separate the ions, and this requires great amounts of energy, thus the melting and boiling points are very high. • CHARACTERISTICS OF IONIC liquids and solutions (aq) • Soluble ionic compounds (table F) form conductive solutions mobile ions. • The melt of an ionic substance is always conductive. • Remember: FOR CONDUCTIVITY – MUST HAVE MOBILITY! (OF IONS OR ELECTRONS)

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