Periodicity Periodic Table Trends

Remember these groups of the periodic table?

Periodic Law There are repeating patterns in the chemical and physical behavior of elements when organized by their atomic number.

Classifying Elements by Electron Configuration e- play significant role in determining physical and chemical properties of elements Elements are arranged by their properties relationship b/w e- config & placement of elements 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 1s22s22p63s23p64s23d104p65s24d105p66s2 4f145d106p67s1 They all end in s1

Every element in group 15 has what outer electron configuration?

Periodic Trends These patterns in electron configurations produce patterns in properties. These patterns are called Periodic Trends.

There are 5 major trends that occur in periodic table: Atomic Mass & Atomic Number Atomic Size Ionic Size Ionization Energy Electronegativity

3 factors that effect Periodic Trends 1. Nuclear Charge (# protons) More p+ = greater charge which pulls e- closer ~ effect s period 2. Energy level More E levels farther away the valence e- ~effects group 3. Shielding effect

Shielding Effect Inner e- blocks the nuclear charge from reaching the valence e- due  E Level +

Atomic Mass & Atomic # Increase from top left to bottom right

Atomic Size (radius)

Atomic Size

Atomic Size - Group trends H Going down a group, atoms add another energy level  atoms get bigger. Li Na K Rb

Atomic Size - Period Trends left to right across a period, the size gets smaller. e- are in the same energy level but more nuclear charge valence e- are pulled closer by inc in protons. Na Mg Al Si P S Cl Ar

Which atom is bigger & Why? Li or Cs Ga or B O or C Be or Ba Si or S

What do you think the word Octet means?

Octet Rule = 8 Gain, lose, or share electrons to become STABLE like Noble gases s2p6 **Exception energy level 1

When atoms are trying to obey the octet rule they will… IONS When atoms are trying to obey the octet rule they will…

Atom loses electron : cation more protons than electrons Group Obeys Octet Rule How Oxidation Number Group 1 loses 1 e- 1+ Group 2 Loses 2 e- 2+ Group 13 Loses 3e- 3+

Atom gained electron: anion more electrons than protons Group How atom obey Octet Rule Oxidation Number Group 15 Add 3 e- 3 - Group 16 Add 2 e- 2 - Group 17 Add 1e- 1 -

Ionic Size Metals: Determine if their ions are smaller or bigger than the neutral atom Nonmetals:

Metal ION ic Size 1. Smaller 2. Lose valence electrons

NonMetal ION ic Size Bigger Gain valence electrons

Metal NonMetal

Which ion in each, is smaller? 1. Al3+ or P3- 2. K+ or Cs+ 3. O2- or Te2-

Ionization Energy (1st) Energy needed to remove ONE electron from an atom …. i.e. “How strongly can atom hold onto it’s valence electrons?”

Ionization Energy

Low Ionization Energy Easy to steal an electron away Analogy: Easy to steal a purse away from a little old lady.

High Ionization Energy Hard to steal an electron away Analogy: Hard to steal a purse away from someone muscular

Going Down a Group Bigger atom= less E to remove e-= lower IE Ionization Energy Decreases…. Valence e- farther from nucleus = not held as tight by nucleus Bigger atom= less E to remove e-= lower IE

Going Across a Period  Smaller atom = more E to remove e-= higher IE Ionization Energy Increases… 1. atom smaller: e- closer to nucleus 2. closer to being a noble gas  Smaller atom = more E to remove e-= higher IE

Which atom has larger (1st ) Ionization Energy ? 1. Na or S 2. Mg or Ba 3. Ga or Br 4. P or Bi

Arrange the following elements in order of decreasing (1st) Ionization Energy? Cs, Li, K Cl, Si, P Ca, Ba, Be, Sr

Electronegativity: bonded elements likelyhood to WANT to take electron from another atom

Electronegativity Like tug of war

Going Down a Group Distance from nucleus increases Electronegativity Decreases… Distance from nucleus increases valence electrons NOT held strongly by nucleus

Going Across Period Electronegativity Increases.. 1. inc attraction to nucleus 2. closer to being a noble gas  it wants an electron

Which atom has higher Electronegativity? Na or Mg K or Br F or Br Ca or Ga Li or S Br or As

Summary Ionization energy decreases Electronegativity decreases Nuclear charge increases Atomic radius increases Shielding increases Shielding is constant Atomic Radius decreases Ionization energy increases Electronegativity increases Nuclear charge increases

Ranking Elements by Atomic Size SAMPLE PROBLEM Ranking Elements by Atomic Size PROBLEM: Using only the periodic table (not Figure 8.15), rank each set of main group elements in order of decreasing atomic size: (a) Ca, Mg, Sr (b) K, Ga, Ca (c) Br, Rb, Kr (d) Sr, Ca, Rb PLAN: Elements in the same group increase in size and you go down; elements decrease in size as you go across a period. SOLUTION: These elements are in Group 2A(2). (a) Sr > Ca > Mg These elements are in Period 4. (b) K > Ca > Ga Rb has a higher energy level and is far to the left. Br is to the left of Kr. (c) Rb > Br > Kr Ca is one energy level smaller than Rb and Sr. Rb is to the left of Sr. (d) Rb > Sr > Ca

(a) Kr, He, Ar (b) Sb, Te, Sn (c) K, Ca, Rb (d) I, Xe, Cs SAMPLE PROBLEM Ranking Elements by First Ionization Energy PROBLEM: Using the periodic table only, rank the elements in each of the following sets in order of decreasing IE1: (a) Kr, He, Ar (b) Sb, Te, Sn (c) K, Ca, Rb (d) I, Xe, Cs PLAN: IE decreases as you proceed down in a group; IE increases as you go across a period. SOLUTION: (a) He > Ar > Kr Group 8A(18) - IE decreases down a group. (b) Te > Sb > Sn Period 5 elements - IE increases across a period. (c) Ca > K > Rb Ca is to the right of K; Rb is below K. (d) Xe > I > Cs I is to the left of Xe; Cs is further to the left and down one period.