Trends of the Periodic Table

1. Trends of the Periodic Table

2. Periodic Table - History • Periodic Table • proposed in 1869 by Russian chemist, Dimitri Mendeleev • combined the concepts of increasing atomic mass and progressive change in valence of the elements • the table would display patterns in the properties of the elements

3. Periodic Table Trends Periodic Table Law: The chemical and physical properties of the elements repeat in a regular, periodic pattern when they are arranged according to their atomic number • The chemical properties of elements are mainly based on: • electron configuration (where the electrons are situated in the atom) • # of valence electrons • location of valence electrons

4. Trends The Trends you are responsible for knowing are: Atomic Size (radius) - How big or small the atoms are Ionization Energy - How easily an atom can lose its electron(s) Electron Affinity - How easily an atom can gain other electron(s) Electronegativity - How willing atoms are in sharing electrons

5. Atomic Size (Radius) As you move DOWNa group, the radius of the atom INCREASES As you move ACROSS a period, the radius of the atom DECREASES http://images.encarta.msn.com/xrefmedia/aencmed/targets/illus/ilt/1e67a7ad.gif

6. H Li Na Atomic Size (Radius) GOING DOWN A GROUP • As you move down a group: • # of electrons increases • valence electrons are further away • # of energy levels increases

7. +3 +4 +5 Li Be B Atomic Size (Radius) GOING Across A Period • As you move across a period: • # of electrons increases but proton increase too! • but energy level stays the same! • More protons = more +ve charge • electrons are pulled towards nucleus more! • Size of atom decreases

8. Ionic Radius Ions = atoms that have lost or gained electrons Ionic Radius pattern is generally has the opposite pattern of the atomic radius http://dwb.unl.edu/Teacher/NSF/C04/C04Images/ionrad.jpg

9. Ionic Radius - Metals Metals: The ionic radius of a metal is generally smaller than its atomic radius Why? • After a metal atom lose its valence e-, • the ion becomes positively charged. • The extra positive charge(s) will attract the • remaining e- toward its nucleus. http://nobel.scas.bcit.ca/chem0010/unit4/images/metalionRadius.jpg

10. Ionic Radius - Nonmetals Non-Metals: The ionic radius of a non-metal is generally larger than its atomic radius Why? • After a non-metal atom gains extra e-, • the ion becomes negatively charged. • The extra negative charge(s) will “overwhelm” the positive charges and will be able to “puff out” away from the nucleus. http://nobel.scas.bcit.ca/chem0010/unit4/images/anionRadius.jpg

11. Ionization Energy Ionization Energy (IE): Amount of energy involved in REMOVING an electron Measured in KJ/mol 2 Reasons to lose electrons: 1) to become isoelectric with the nearest noble gas 2) to eliminate a near-empty outer energy level 1st Ionization Energy --> The amount of energy required to remove ONE electron from the outer energy level. 2nd Ionization Energy --> The amount of energy required to remove a SECOND electron from the outer energy level.

12. Ionization Energy As you move DOWNa group, the IE of the atom DECREASES As you move ACROSS a period, the IE of the atom INCREASES

13. H Li Na Ionization Energy GOING DOWN A GROUP • As you move down a group: • the outermost electrons are further from the proton in the nucleus • protons cannot “grab” onto outer electrons as easily • outer electrons become easier to remove • takes less energy to remove outer electrons

14. +3 +4 +5 Li Be B Ionization Energy GOING Across A Period • As you move across a period: • # of proton increase • energy level stays the same! • More protons = more +ve charge • electrons are pulled towards nucleus more! • Harder to remove electrons • More energy is required to remove an electron

15. Electron Affinity Electron Affinity: Change in energy that occurs whenan electron is added to the valence energylevel of an atom NEGATIVE value = Energy is released when an atom gains an e- Reaction would happen “easily” The more negative the value, the more “easily” it gains an e- POSTIVE value = Energy is absorbed when an atom gains an e- Reaction would NOT happen easily…energy must be added The more positive the value, the harder it is to gain an e-

16. Electron Affinity As you move DOWNa group, the EA of the atom becomes more POSITIVE As you move ACROSS a period, the EA of the atom becomes more NEGATIVE Exceptions: Group 2 and Noble Gases

17. Electron Affinity Values in graph are NEGATIVE. Flat bars indicate positive values http://www.webelements.com/webelements/properties/media/tables/cityscape-x/electron-affinity.jpg

18. F Cl Electron Affinity GOING DOWN A GROUP • As you move down a group: • the valence shells become further from the proton in the nucleus • protons will have a harder time attracting & getting an electron from outside. • EA value becomes more positive

19. +3 +9 F Li Electron Affinity GOING Across A Period • As you move across a period: • # of proton increase • energy level stays the same! • More protons = more +ve charge • more able to “grab” outside electron • Towards the right side of the period, it becomes more easier to gain an electron to fill valence shell than to lose many electrons. Yes! One more ELECTRON to fill the shell!!!! Not interested!

20. O H H Electronegativity Electronegativity: One atom’s ability to “hog” electrons that are shared between 2 atoms in a molecule Oxygen is more electronegative Oxygen “hogs” electron Oxygen is less electronegative The more it is able to “hog” electrons, the higher the electronegativity

21. Electronegativity As you move DOWNa group, the ENDECREASES As you move ACROSS a period, the ENINCREASES http://colossus.chem.umass.edu/genchem/whelan/class_images/Electronegativity_Table.gif

22. F H Cl H Electronegativity GOING DOWN A GROUP • As you move down a group: • the valence shells become further from the proton in the nucleus • protons will have a harder time hogging an electron from the other atoms in the molecule. • EN becomes smaller HF HCl

23. +6 +9 H H F Electronegativity GOING ACROSS A PERIOD • As you move across a period: • # of proton increase • energy level stays the same! • More protons = more +ve charge • more able to “hog” electron from its partner • Towards the right side of the period, it becomes more easier to have access to an electron to fill valence shell than to give away many electrons to the partner C