Introduction to Periodic Trends

Remember these groups of the periodic table?

The Periodic Law When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.

Classifying Elements by Electron Configuration Remember…electrons play the most significant role in determining physical and chemical properties of elements. Elements are arranged in the table according to their properties. Therefore, there should be some relationship between the electron configurations of the elements and their placement in the table.

How the configurations of the noble gases similar? 1s22s22p6 1s22s22p63s23p6 1s22s22p63s23p64s23d104p6 1s22s22p63s23p64s23d104p65s24d105p6 1s22s22p63s23p64s23d104p65s24d10 5p66s24f145d106p6 2 Ne 10 The outer energy level is completely full! Ar 18 Kr 36 Xe 54 Rn 86

How are the configurations of the alkali metals similar? 1 Li 3 Na 11 K 19 Rb 37 Cs 55 Fr 87 1s1 1s22s1 1s22s22p63s1 1s22s22p63s23p64s1 1s22s22p63s23p64s23d104p65s1 1s22s22p63s23p64s23d104p65s24d10 5p66s1 1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p67s1 They all end in s1!

Alkaline earth metals all end in s2. He s2 Alkaline earth metals might include He, but He fits better with the noble gases. He has similar properties to the noble gases because its outer energy level is completely full. How would the halogens all end? p5

Transition Metals - d block The outer s sublevel is full and the d sublevel is now filling. Why is there a change in configuration? s1 d5 s1 d10 d1 d2 d3 d5 d6 d7 d8 d10 Half-filled sublevels are more stable.

Periodic Trends These patterns in electron configurations produce patterns in properties. These patterns are called Periodic Trends. Can be followed either across a period or down a group

Four Trends Atomic Size Ion Size Electronegativity Ionization Energy

Influenced by three factors: 1. Energy level Periodic Trends Influenced by three factors: 1. Energy level At higher energy levels the electron is further away from nucleus. 2. Charge on nucleus (# protons) More protons means a greater charge pulls electrons in closer. 3. Shielding effect

Problem: Where do you start measuring from? Trends in Atomic Size Problem: Where do you start measuring from? The electron cloud doesn’t have a definite edge. This problem is solved by measuring more than 1 atom at a time.

} Trends in Atomic Size Radius Measure the distance between the two nuclei of a diatomic molecule. Half of this distance is the atomic radius.

Diatomic Molecules 7 elements Beginning with element 7 Form the number 7 (except H) Never alone If they are not with another element, they bond with themselves. 1 H He 2 Li Be S C N O F Ne 3 Na Mg Al Si P Cl Ar 4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 5 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe 6 Cs Ba La   Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 7 Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg Uub — Uuq 7

Atomic Size - Group Trend H As we go down a group… Each atom has another energy level So the atoms get bigger. Li Na OBVIOUS!! K Rb

Atomic Size - Period Trend Going from left to right across a period, the size gets smaller. Electrons are in the same energy level. But, there is more nuclear charge (more protons). So…outermost electrons are pulled in closer. NOT SO OBVIOUS!! Na Mg Al Si P S Cl Ar

Atomic radius increases Atomic radius decreases Atomic radius increases