Electron Configuration

 In atomic physics and quantum chemistry, electron configuration is the arrangement of electrons of an atom. electrons

Electron Shells  Electron configuration was first conceived of under the Bohr model of the atom. Bohr modelBohr model  What does Bohr’s model look like? 8P 8N

Valence Electrons  How many electrons are in the valence shell of this atom?  What is the “magic number”? 8

Element Groups  Let’s take a look at the different Groups on the Periodic Table.  Each Group has a specific number of electrons in its outer shell (we won’t look at the transition metals, as they are a bit more complicated).  Do you remember the names of each of the Periodic Table Groups? Group 1 = Alkali Metals Group 1 = Alkali Metals Group 2 = Alkaline Earth Metals Group 2 = Alkaline Earth Metals Group 3-12 = Transition Metals Group 3-12 = Transition Metals Group 13 = Boron Family Group 13 = Boron Family Group 14 = Carbon Family Group 14 = Carbon Family Group 15 = Nitrogen Family Group 15 = Nitrogen Family Group 16 = Oxygen Family Group 16 = Oxygen Family Group 17 = Halogen Family Group 17 = Halogen Family Group 18 = Noble Gases Group 18 = Noble Gases

Group 1 – Alkali Metals  This Group of elements has 1 electron in its outer shell. How can we remember this? How can we remember this?  Is it going to want to gain or lose an electron to be stable? Each will choose to lose an electron becoming a positive ion. Each will choose to lose an electron becoming a positive ion. 1H1H 3 Li Li 11 Na Na 19 K K 37 Rb Rb 55 Cs Cs 87 Fr

Group 2 – Alkaline Earth Metals  This Group of elements has 2 electrons in its outer shell. How can we remember this? How can we remember this?  Will they gain or lose electrons and how many? They will lose 2 electrons to become positive ions. They will lose 2 electrons to become positive ions. 4 Be Be 12 Mg Mg 20 Ca Ca 38 Sr Sr 56 Ba Ba 88 Ra Ra

Group 13 – Boron Family  The Boron Group has 3 electrons in the outer shell. How can we remember this? How can we remember this? Are you starting to see a pattern? Are you starting to see a pattern?  What will the elements choose to do about attaining their 8 valence electrons? The elements of this Group will choose again to lose 3 electrons becoming positive ions. The elements of this Group will choose again to lose 3 electrons becoming positive ions. 5B5B 13 Al Al 31 Ga Ga 49 In In 81 Tl Tl

Group 14 – Carbon Family  How many electrons does this Group have in its outer shell? 4  What will each choose to do with those electrons? Since there are 4 electrons, half of 8, in the outer shell, this Group is more flexible in its gaining and losing. Since there are 4 electrons, half of 8, in the outer shell, this Group is more flexible in its gaining and losing. The atoms will gain or lose electrons as needed to form compounds. The atoms will gain or lose electrons as needed to form compounds. This is the only Group that will do this to become either cations or anions. This is the only Group that will do this to become either cations or anions. 6 C 14 Si Si 32 Ge Ge 50 Sn Sn 82 Pb Pb 114 Uuq Uuq

Group 15 – Nitrogen Family  How many electrons are in the outer shell of each of these atoms? 5  How do you think the atoms of this Family will attain their stable configuration of valence electrons? This group will gain 3 electrons to become negative ions. This group will gain 3 electrons to become negative ions. 7N7N 15 P P 33 As As 51 Sb Sb 83 Bi Bi 115 Uu p Uu p

Group 16 – Oxygen Family  The atoms of this Group have how many electrons in the outer shell? 6  Describe what the elements of this Group will do to attain their stable valence electron configuration? The atoms will gain 2 electrons to become negative ions. The atoms will gain 2 electrons to become negative ions. 8O8O 16 S S 34 Se Se 52 Te Te 84 Po Po 116 Uu h Uu h

Group 17 – Halogen Family  Tell me how many electrons the atoms from this Group have in the outer shell? 7  What will the atoms of this Group do to attain the stable valence electron configuration? The atoms from this Group will again choose to gain electrons. The atoms from this Group will again choose to gain electrons. How many will they gain? How many will they gain? 1 9F9F 17 Cl Cl 35 Br Br 53 I I 85 At At (117) (Uus) (Uus)

Group 18 – Noble Gases  How many electrons are in the outer shell of this Group’s atoms? 8  Will this Group gain or lose electrons? Neither, this Group’s valence electron configuration is stable; and, the elements do not react to form compounds as a result. Neither, this Group’s valence electron configuration is stable; and, the elements do not react to form compounds as a result. 2 He He 10 Ne Ne 18 Ar Ar 36 Kr Kr 54 Xe Xe 86 Rn Rn 118 Uuo Uuo

Let’s Practice  What element does this Bohr model represent? Oxygen Oxygen 8P 8N

More Practice…  What element does this Bohr model represent? Chlorine Chlorine 17P 18N

More Practice…  What element does this Bohr model represent? Magnesium Magnesium 12P 12N

Electron Shell Configuration…  Each shell has a set number of electrons.  For those atoms that have electrons in the 3 rd or higher shells: the next to the last shell needs to have 8 in it if the atom is going to lose the electrons in its outer shell (there are a few exceptions to this rule). Shell Max # e- 1 st 2 2 nd 8 3 rd 18 4 th 32