Periodicity Periodic Table Trends Remember these groups of
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? 1 s 2 He 2 Ne 1 s 22 p 6 10 The outer energy level is completely full! 1 s 22 s 22 p 63 s 23 p 64 s 23 d 104 p 6 1 s 22 p 63 s 23 p 64 s 23 d 104 p 65 s 24 d 105 p 6 1 s 22 p 63 s 23 p 64 s 23 d 104 p 65 s 24 d 10 5 p 66 s 24 f 145 d 106 p 6 Ar 18 Kr 36 Xe 54 Rn 86
H Li 1 1 s 1 3 1 s 22 s 1 Na 11 K 19 Rb 37 Cs 55 Fr 87 How are the configurations of the alkali metals similar? 1 s 22 p 63 s 1 They all end in 1 s 1 s 22 p 63 s 23 p 64 s 1 1 s 22 s 22 p 63 s 23 p 64 s 23 d 104 p 65 s 24 d 10 5 p 66 s 1 1 s 22 p 63 s 23 p 64 s 23 d 104 p 65 s 24 d 105 p 66 s 24 f 145 d 106 p 67 s 1
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 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 edue E Level +
Atomic Mass & Atomic # Increase from top left to bottom right
Atomic Size (radius)
Atomic Size
Atomic Size - Group trends Going down a group, atoms add another energy level atoms get bigger. H 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
Nucleus Strength
Which atom is bigger & Why? 1. Li or Cs 2. Ga or B 3. O or C 4. Be or Ba 5. 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 s 2 p 6 **Exception energy level 1
IONS When atoms are trying to obey the octet rule they will…
Cation (+) 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 3 e- 3+
Anion (-) 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 1 e- 1 -
Ionic Size Metals: Determine if their ions are smaller or bigger than the neutral atom Nonmetals: Determine if their ions are smaller or bigger than the neutral atom
Metal ION ic Size 1. Smaller 2. Lose valence electrons
Non. Metal ION ic Size 1. Bigger 2. Gain valence electrons
Metal Non. Metal
Which ion in each, is smaller? 1. Al 3+ or P 32. K+ or Cs+ 3. O 2 - or Te 2 -
Ionization Energy (1 st) 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 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 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
Ionization Energy 2 nd IE is the E required to remove the 2 nd e Always greater than first IE. 3 rd IE is the E required to remove a third e Greater than 1 st & 2 nd IE
Which atom has larger (1 st ) 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 (1 st) Ionization Energy? 1. Cs, Li, K 2. Cl, Si, P 3. Ca, Be, Sr
Electronegativity: bonded elements likelyhood to WANT to take electron from another atom
Electronegativity Like tug of war
Going Down a Group 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? 1. 2. 3. 4. 5. 6. Na or Mg K or Br F or Br Ca or Ga Li or S Br or As
Nuclear charge increases Shielding increases Atomic radius increases Ionization energy decreases Electronegativity decreases Summary Shielding is constant Atomic Radius decreases Ionization energy increases Electronegativity increases Nuclear charge increases
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: (a) Sr > Ca > Mg (b) K > Ca > Ga These elements are in Group 2 A(2). These elements are in Period 4. (c) Rb > Br > Kr Rb has a higher energy level and is far to the left. Br is to the left of Kr. (d) Rb > Sr > Ca Ca is one energy level smaller than Rb and Sr. Rb is to the left of Sr.
SAMPLE PROBLEM: Using the periodic table only, rank the elements in each of the following sets in order of decreasing IE 1: (a) Kr, He, Ar PLAN: Ranking Elements by First Ionization Energy (b) Sb, Te, Sn (c) K, Ca, Rb (d) I, Xe, Cs IE decreases as you proceed down in a group; IE increases as you go across a period. SOLUTION: (a) He > Ar > Kr Group 8 A(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.
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