Periodic Trends in the Properties of the Elements

Reactivity Metals: as you move down a family, reactivity goes up. As you move across a period, reactivity goes down. Brainiac’s Video Nonmetals: as you move down a family, reactivity goes down. As you move across a period, reactivity goes up. Except for the Noble Gases!!!!

Atomic Size Either volume or radius. Treat atom as a hard marble. As you move down a column on the periodic table, the size of the atom increases. Valence shell farther from nucleus. As you move left to right across a period, the size of the atom decreases. Adding electrons to same valence shell. Valence shell held closer.

Trends in Atomic Size, Continued

Be (4p+ and 4e-) Mg (12p+ and 12e-) Ca (20p+ and 20e-) Group IIA 2e-

Li (3p+ and 3e-) Be (4p+ and 4e-) B (5p+ and 5e-) C (6p+ and 6e-) Period 2 2e- 1e- 3 p+ 2e- 4 p+ 2e- 3e- 5 p+ Li (3p+ and 3e-) Be (4p+ and 4e-) B (5p+ and 5e-) 6 p+ 2e- 4e- 8 p+ 2e- 6e- 10 p+ 2e- 8e- C (6p+ and 6e-) O (8p+ and 8e-) Ne (10p+ and 10e-)

Choose the Larger Atom in Each Pair C or O Li or K C or Al Se or I?

Practice—Choose the Larger Atom in Each Pair. 1. N or F 2. C or Ge 3. N or Al 4. Al or Ge

Practice—Choose the Larger Atom in Each Pair, Continued. N or F, N is further left N or F C or Ge N or Al, Al is further down & left N or F C or Ge, Ge is further down N or F C or Ge N or Al Al or Ge? opposing trends

Ionization Energy Minimum energy needed to remove an electron from an atom. Valence electron easiest to remove. M(g) + 1st IE  M1+(g) + 1 e- M+1(g) + 2nd IE  M2+(g) + 1 e- First ionization energy = energy to remove electron from neutral atom; 2nd IE = energy to remove from +1 ion; etc.

Trends in Ionization Energy As you move down a family, the IE gets smaller. Valence electron farther from nucleus. As you move left to right across a period, the IE gets larger.

Trends in Ionization Energy, Continued

Example—Choose the Atom in Each Pair with the Higher First Ionization Energy Al or S, Al is further left 1. Al or S 2. As or Sb 3. N or Si 4. O or Cl, opposing trends Al or S As or Sb N or Si, Si is further down and left Al or S As or Sb, Sb is further down

Practice—Choose the Atom with the Highest Ionization Energy in Each Pair 1. Mg or P 2. Cl or Br 3. Se or Sb 4. P or Se

Practice—Choose the Atom with the Highest Ionization Energy in Each Pair, Continued 1. Mg or P 2. Cl or Br 3. Se or Sb 4. P or Se ?

Metallic Character How well an element’s properties match the general properties of a metal. In general, metals are found on the left of the periodic table and nonmetals on the right. As you go left to right across the period, the elements become less metallic. As you go down a column, the elements become more metallic

Trends in Metallic Character

Example—Choose the More Metallic Element in Each Pair Sn or Te, Sn is further left Sn or Te P or Sb Ge or In S or Br? opposing trends Sn or Te P or Sb Ge or In, In is further down & left Sn or Te P or Sb, Sb is further down

Practice—Choose the More Metallic Element in Each Pair Sn or Te Si or Sn Br or Te Se or I

Practice—Choose the More Metallic Element in Each Pair, Continued Sn or Te Si or Sn Br or Te Se or I ?

Electronegativity Measure of the pull an atom has on bonding electrons. Increases across the period (left to right). Decreases down the group (top to bottom). The larger the difference in electronegativity, the more polar the bond. Negative end toward more electronegative atom. d+ H — F d-

Electronegativity, Continued 2.1 1.0 0.9 0.8 0.7 1.5 1.2 1.3 1.1 1.4 1.6 1.8 1.7 1.9 2.2 2.4 2.0 2.5 3.0 3.5 4.0 2.8

Electronegativity, Continued

Melting/Boiling Point High melting/boiling point indicates strong bonding Middle of Periodic Table Low melting/boiling point indicates weak bonding Lowest MP/BP across period indicates completely filled orbital Edges of Periodic Table Noble gases have no bonding forces MP/BP unusually low

Melting/Boiling Point