2. Introduction to the Periodic Table

3. I. History of the Periodic Table Demitri Mendeleev Demitri Mendeleev (1860’s Russia) Arranged known elements: – by mass – in vertical columns by Phs/Chem Prop. Left blank spaces (very accurate!) Published his PT in 1871

4. Henry Mosley Henry Mosley (1913) Arranged the PT by atomic number “Father” of the modern periodic table As time passed: *more elements were discovered *when placed by P/C properties, masses were out of order

5. II. The Modern Periodic Table A. Includes: 1. periods/rows 2. groups/families There are 4 categories of groups: 1.Representative (Main Group Elements) 2.Transition elements 3.Inner transition (Lanthanides/ Actinides) 4.Noble Gases Some groups have special names: –1A (Alkali Metals) –2A (Alkaline Earth Metals) –7A/group 17 (Halogens) –8A/group 18 (Noble Gases) The letters A and B in the group distinguish families –A = representative –B = transition

7. Properties and Trends Electron Configurations

8. Metallic Character i)L to R: metals to nonmetals ii) Nonmetals are at the right of the Table. They tend to be insulators and react easily with metals. iii) Metalloids separate the metals and nonmetals and have intermediate properties

9. Atomic Radius –Atomic radius – half distance between the nuclei of two atoms of same element –Atomic radius increases as you move down the groups Greater distance from nucleus = less pull towards center –Decreases as you move left to right More pull from nucleus (more protons), but no new distance –EXCEPTION: Noble Gases – much bigger than group 17 – full outer shell

11. Atomic Radii

12. Ionization Energy –Ion – atom which has gained or lost electrons Cation – (+) charged ion (lost e - ) Anion – (-) charged ion (gained e - ) –Ionization energy – the energy that is required to remove an e - from an atom –Decreases as you move down the periodic table Outer e- gets further from nucleus, easier to pull off –Increases as you move left to right No more distance from nucleus, but more p+

13. Ionization Energy

14. Electron Affinity –Electron Affinity – the energy change that occurs when an electron is ADDED to a neutral atom Bigger negative number = easier to add e - –Harder to add as you go down a group Further distance from nucleus & more inner e - = more repulsion –Easier to add from left to right Increased p+, more attraction to nucleus –Halogens gain most easily, they want to complete that ‘perfect eight’/ Noble Gases – don’t accept e -

15. Electron Affinity

17. Ionization Energy vs. Electron Affinity

18. Ionic Size (Radius) –Ionic Radius- ½ the distance between the nuclei of two ions –Cations (+) are always SMALLER than neutral atom Nuclear charge the same, less e - –Anions (-) are always LARGER than neutral atom Nuclear charge the same, MORE e - –Increases as you go down a group –Decreases from left to right

19. Ionic Radii

20. Electronegativity –Electronegativity – tendency for an element to have a stronger pull on the shared e - in a covalent bond (values btwn 0-4) –Decreases down a group – less likely to keep the shared e - –Increases from left to right – more likely to have the shared e -

21. Electronegativity