Using only the Periodic Table, be able to give the electron configuration of any Main Group element and the first row transition metals.

Transcription

1 Using only the Periodic Table, be able to give the electron configuration of any Main Group element and the first row transition metals. 1

2 Location on Periodic Table of the Elements is related to electron configuration Elements in the same row (family) have the same valence shell configuration. Example: alkali metals (row 1) have ns 1 valence configuration (H) 1s 1 Li [He]2s 1 Na [Ne]3s 1 K [Ar]4s 1 Rb [Kr]5s 1 Cs [Xe]6s 1 halogens (F, Cl, Br, I) have np 5 outer-shell noble gases (inert) have filled outer-shell np 6 Valence electrons determine the chemistry! 2

3 The PROPERTIES OF ELEMENTS are related to their structure. Electron Configurations = structure of the atom Electron configurations determine the organization of the Periodic Table AND the properties of the elements: reason for periodic trends in behavior Properties of elements are determined by: Size (n) and shape ( ) of orbitals Atomic number (nuclear charge) Elemental properties: atomic size Ionization energy electron affinities reactivity 3

4 Atomic radius is the half distance between bonded atoms Trends in atomic radii size increases going down group WHY? 4

5 Atomic size decreases going from left to right across a period WHY? 5

6 ELECTRON CONFIGURATIONS OF IONS: Elements gain or lose electrons to form separate ions with complete octets. e Na Cl 1s 2 2s 2 2p 6 3s 1 1s 2 2s 2 2p 6 3s 2 3p 5 core electrons valence electrons Na + Cl 1s 2 2s 2 2p 6 1s 2 2s 2 2p 6 3s 2 3p 6 [Ne] [Ar] complete octets 6

7 Charges of Common Ions can be predicted by their location on the Periodic Table 7

8 The trends in ION SIZES can be predicted. cations are smaller than parent atoms Na Na Å 0.96Å anions are larger than parent atoms Cl Cl 0.99Å 1.81Å 8

9 Ion size increases going down family (same as trend in atom size) Li + F Na + Cl K + Br Rb + I Size increases 9

10 ISOELECTRONIC SERIES is a group of atoms or ions that have the same # of electrons (have the same ground state electron configuration) Example: # electrons? O 2 F Na + Mg 2+ Al 3+ nuclear charge size 10

11 IONIZATION ENERGY is the energy needed to remove an electron I 1 First ionization energy I 1 I 2 Second ionization energy I 2 etc

12 IONIZATION ENERGY: Outer (valence) electrons are more easily removed. Example: Mg 1s 2 2s 2 2p 6 3s 2 [Ne] valence electrons core electrons I 1 = 738 kj/mol Mg + (g) [Ne] 3s 1 I 2 = 1451 kj/mol Mg +2 (g) [Ne] I 3 = 7733 kj/mol Mg +3 (g) 1s 2 2s 2 2p 5 12

13 IONIZATION ENERGY: Outer (valence) electrons are more easily removed. Chem

14 TRENDS in IONIZATION ENERGY: The further the electron is from the nucleus the easier it is to remove. going down a family I 1 (kj/mol) Li 510 Size? Na 490 I.E. K 418 increases Rb 403 Cs

15 TRENDS in IONIZATION ENERGY: The further the electron is from the nucleus the easier it is to remove. across the periodic table Na Mg Al Si P S Cl Ar I 1 (kj/mol) I 1 increases from left to right (some exceptions) I.E size BUT THERE ARE SOME EXCEPTIONS 15

16 There are exceptions to the trends in Ionization Energy It takes extra energy to remove electrons from filled subshells (Mg, Ar) or half filled subshells (P) 16

17 ELECTRON AFFINITIES: Energy needed to add an electron to an atom or ion in the gas phase Textbook definition does NOT follow our standard sign convention but describes the same thing.. If energy is released: Positive or negative??? Cl(g) + e è Cl (g) E.A. = 349kJ/mol 17

18 ELECTRON AFFINITIES: Energy needed to add an electron to an atom or ion in the gas phase Trends in Electron Affinity (EA) are not obvious. Notice when EA releases energy or absorbs energy Releases energy: Halogens: one added electron completes the octet Group I metals : added electron results in filled n s 2 subshell Absorbs energy: Group II metals (Be, Mg, Ca): already have a filled n s 2 subshell Noble gases: already have complete octet 18

19 Metals are to the right and nonmetals are on the upper left on the Periodic Table. 19

20 The reactivity of METALS is related to the ionization energy. 2Li(s) +2H 2 O( ) 2Li + (aq) +2OH (aq)+h 2 (g) 2Na(s)+2H 2 O( ) 2Na + (aq)+2oh (aq)+h 2 (g) 2K(s) +2H 2 O( ) 2K + (aq) +2OH (aq)+h 2 (g) Li Be Na Mg K Ca Rb Sr Reactivity as ionization energy (IE = energy need to form a positive ion) 20

21 The reactivity of NONMETALS is related to the electron affinity. 2KCl(aq) + Br 2 (aq) 2KCl(aq) + I 2 (aq) 2KBr(aq) + I 2 (aq) no reaction no reaction no reaction 2KBr(aq) + Cl 2 (aq) 2KCl(aq) + Br 2 (aq) 2KI(aq) + Cl 2 (aq) 2KCl(aq) + I 2 (aq) 2KI(aq + Br 2 (aq) 2KBr(aq) + I 2 (aq) Cl 2 more reactive than Br 2 or I 2 Br 2 more reactive than I 2 F 2 electron Cl 2 reactivity affinity Br 2 I 2 Reactivity increases as electron affinity increases 21