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Periodic Properties. Periodic Trends Don’t Confuse a trend with the explanation for that trend!!!!! Example- Why is Br atom larger than a Kr atom?????

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Presentation on theme: "Periodic Properties. Periodic Trends Don’t Confuse a trend with the explanation for that trend!!!!! Example- Why is Br atom larger than a Kr atom?????"— Presentation transcript:

1 Periodic Properties

2 Periodic Trends

3 Don’t Confuse a trend with the explanation for that trend!!!!! Example- Why is Br atom larger than a Kr atom????? Why is a cation smaller than its parent atom? Why is an anion larger than its parent atom??

4 Ionization energy Endothermic –requires energy to remove outermost electron Decreases down a group- large atomic radium and sheilding effect means that less energy needed to remove electrons Increases across a period, the effextive nuclear charge increases, which causes an increased attraction between valence elctron and proton

5 Ionization Energy- Why drop Be to B and N to O

6 Ionization Energy Exceptions

7 What happens to the IE as increasing number of electrons are removed from an atom? Where do the “jumps” occur? I 1 < I 2 < I 3

8 Electron Affinity Energy released when an atom attracts an addition electron Negative- exothermic process More negative, the greater the affinity Elements in Group 2, 15 and 18 have lower than expected EA because of full (s) or ½ full (diamagnetic)(p) sublevels-electron=electron repulsion

9 Sample MC Questions 1-3refer to the following elements a. O b.La c.Rb d.Mg e.N 1.What is the most electronegative element of the above? 2.Which element exhibits the greatest number of different oxidation states? 3.Which of the elements above has the smallest ionic radius for its most commonly found ion?

10 Sample MC 4. The effective nuclear charge experienced by the outermost electron of Na is different than the effective nuclear charge experienced by the outermost electron of Ne. This difference best accounts for which of the following? a.Na has a greater density at standard conditions than Ne. b.Na has a lower first ionization energy than Ne. c.Na has a higher melting point than Ne. d.Na has a higher neutron-to-proton ration than Ne. e.Na has fewer naturally occurring isotopes than Ne.

11 MC Sample 5

12 Chemical Bonding Types: ionic- cation and anion covalent- nonmetal+ nonmetal Metallic- metal + metal- cations surrounded by a sea of electrons, valence electrons are delocalized

13 Ionic Lattice energy- amount of energy needed to separtate 1 mole of an ionic compound into its gaseous ions Lattice energy increases with: smaller, more highly charged atoms—Coloumb’s law E= k Q 1 Q 2/d Q 1 and Q 2 are charges on ions, d is distance between ions

14 Covalent Electronegativity difference determines polarity- 0-0.3; 0.3-1.7, 1.7 and greater Dipole- molecule having one end with a slight + charge and the otherend with a slight negative charge

15 Lewis Structures 1. Count number of valence electrons 2. Find central atom 3. place outer atoms around central atom with single bond, place valence lectrons to give them an octet 4. Determine if there are enough electrons to give central atom octet. If not, multiple bonds! Try Sulfur trioxide!

16 Formal Charge Determines best lewis structure. Equal to # VE-# nonbonding electrons-1/2 number of bonding electrons Formal charges of 0 means more likely Lewis structure Example CO 2

17 Exceptions to Octet Rule Central atom is Be (4 VE) BeI 2 B(6 VE) BF 3 Species has an odd # electrons, one atom will have only 7 electrons (NO) Expanded octet: Larger nonmetal central atom (period 3 and beyond) have d orbitals available for bonding. Also, the larger the atom, the more atoms that can fit around it: SF 6, PCl 5, XeF 4


19 Sigma and pi bonds Single bond—sigma Double bond—one sigma and one pi bond Triple bond- one sigma, and 2 pi bonds

20 MC practice (A) CaO (B) CH2CH 2 (C 2 H 4 ) (C) SeO 3 (D) CH 2 Cl 2 (E) NBr3 1. The molecule with only one pi bond 2. The molecule whose molecular geometry is different from its electron geometry 3. The molecule that has trigonal pyramidal geometry

21 MC practice 4.Which of the following molecules has the shortest bond length? A) N2 B) O2 C) Cl2 D) Br2 E) I2

22 MC practice 5. For which of the following molecules is the concept of resonance most likely to describe the bonding satisfactorily? A) BeF2 B) NO 2 - C) CO 2 D) CN - E) PCl5

23 MC Practice 6. CCl4, CO2, PCl3, PCl5, SF6 Which of the following does not describe any of the molecules above? A) Square planar B) Tetrahedral C) Trigonal pyramidal D) Linear E) Octahedral

24 MC Practice 7. All of these molecular shapes can be explained by sp3d hybridization of electrons on the central atom except A) linear B) a square pyramid C) see-saw D) a trigonal bipyramid E) an octahedron

25 MC Practice 8. The melting point of MgO is higher than that of NaF. Explanations for this observation include which of the following? I. Mg 2+ is more positively charged than Na + II. O 2– is more negatively charged than F – III. The O 2– ion is smaller than the F – ion A) II only B) I and II only C) I and III only D) II and III only E) I, II, and III

26 Electrons and wave properties



29 Calcuating among wavelength frequency and energy

30 Balmer series Hydrogen BLS



33 A line having a wavelength of 656 nm exists in the atomic emission spectrum of hydrogen For the line, calcuate the: A. frequency B. energy of the photon C. energy of a mole of photons D. discuss th origin of the line in terms of the Bohr model of the atom


35 Electron Configuration Rules


37 Periodic table electron configuration

38 MC Practice Questions 1-4 refer to the following electron configurations. I.1s 2 2s 2 2p 5 3s 2 3p 5 II.1s 2 2s 2 2p 6 3s 2 3p 6 III.1s 2 2s 2 2p 6 2d 10 3s 2 3p 6 IV.1s 2 2s 2 2p 6 3s 2 3p 6 3d 5 V.1s 2 2s 2 2p 6 3s 2 3p 6 3d 3 4s 2 1.The ground-state configuration for the atoms of a transition element. 2.The ground-state configuration of a negative ion of a halogen. 3.The ground-state configuration of a common ion of an alkaline earth element. 4.An impossible electronic configuration.

39 MC Practice a)1s____2s  b)1s  2s  c)1s  2s  2p   d)1s  2s  2p      e)[Ar] 4s  3d      5. Represents an atom that has four valence electrons. 6. Represents an atom that is chemically unreactive. 7. Represents an atom in an excited state

40 MC Practice 8. For which of the following electron transitions for a hydrogen atom does the light emitted have the longest wavelength? a.n=5 to n=4 b.n=5 to n=2 c.n=3 to n=2 d.n=5 to n=3 e.n=4 to n=3

41 MC Practice 9. Sr, Cr, Co, Hg, P Gaseous atoms of which of the elements above are paramagnetic? a.Sr and P only b.Hg and P only c.Mg, Cr, and Co only d.Cr, Co, and P only e.Cr, Co, and Hg only

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