Lecture 18 © slg Chemistry 151 Review, Electronic Configuration of Atoms Electronic Configuration of Ions Magnetism TOPICS:

Review, Electronic Configuration of Atoms Let’s start by doing a complete set of configurations for lead, Pb, Z= 82 The first step: find element in periodic table noting: a) which block (s, p, d, f) b) which period c) which column

Pb, Z =82, 6th period, Column 4A 6p 2 1A 2A 3A 4A 5A 6A 7A 8A Period 6 Period 1

Pb, Z= 82 p block 6th period Column 4A “6p 2 ” Locates shell (n# for s,p = period #) Locates last e in place in orbital 6p 6p 6p Places last e in subshell

1s 2 ) 2 2s 2 2p 6 ) 10 3s 2 3p 6 ) 18 4s 2 3d 10 4p 6 ) 36 5s 2 4d 10 5p 6 ) 54 6s 2 5d 1 4f 14 5d 9 6p 2 ) 82 4f 14 5d 10 summarize! Short, order of filling: Xe 54 6s 2 4f 14 5d 10 6p 2 Short, order of shells: Xe 54 4f 14 5d 10 6s 2 6p 2 Four outer shell, valence electrons; group 4A; once the inner shell d’s and f’s are full: core electrons Long form, order of filling, from PT:

Group Work: Ag, Z= 47 Short: Order of Filling Short: Order of Shells Sb, Z= 51 Short: Order of Filling Short: Order of Shells Rf, Z= 104 Short: Order of Filling Short: Order of Shells Circle valence electrons in short form, order of shells

Key: Ag, Z= 47 Short, Order of Filling: [Kr 36 ] 5s 2 4d 9 5s 1 4d 10 Short, Order of Shells: [Kr 36 ] 4d 9 5s 2 4d 10 5s 1 Sb, Z= 51 Short: Order of Filling [Kr 36 ] 5s 2 4d 10 5p 3 Short: Order of Shells [Kr 36 ] 4d 10 5s 2 5p 3 Rf, Z= 104 Short: Order of Filling [Rn 86 ] 7s 2 5f 14 6d 2 Short: Order of Shells [Rn 86 ] 5f 14 6d 2 7s 2

Electronic Configuration of Ions The electronic configurations we have developed give the basis for the charges we have already assigned to many elements when they are found as ions in an ionic type compound. The main group elements (columns 1A-8A) lose, gain or share valence electrons in forming compounds so that they can achieve an outer shell configuration, when possible, of the nearest noble gas.

When electrons are transferred from one element to another, charged particles called ions are formed. We have already assigned a positive charge, equal to the column number, for ions formed from elements in columns 1A, 2A and selected 3A elements. Note how this correlates with configurations we have done:

Column 1A: All Ions, +1 Nearest noble gas

Since all 1A elements share the same outer shell configuration, “s 1 ”, they are all expected to form the same charged ion, +1. All elements in column 2A, with the outer shell configuration of “s 2 ” show a + 2 charge, losing both these electrons to form the noble gas configuration:

Column 2A: All Ions, +2

In the p block, elements filling the p subshell, both cations and anions are formed: let’s consider the cations first... Aluminum, in group 3A, loses outer s and p electrons to form a + 3 cation: Other metals in the p block show variable charges, losing either the p e’s only or the p’s and s’s

P Block metals: Variable Charges Also: Ga, In: 1 +, 3 + ; Sn, 2 +, 4 + ; lower charges more common

Anions of the P Block The non-metals in columns 5, 6 and 7 are most likely to form monoatomic anions; the metalloids of these groups are less likely to be found as these anions. In all cases, these elements gain sufficient e’s to become “isoelectric” with following noble gas. “ISOELECTRIC”: same number of electrons

Anions Isoelectric with Neon: N 3- O 2- F 1-

Anions Isoelectric with Argon: P 3- S 2- Cl 1-

Let us consider the “variable charge” transition elements: these metals can utilize both their outer s and their inner d electrons for ion formation, and they are not as likely to revert to a noble gas in the process: In forming ions, the outermost electrons, the “s” e’s, are lost first to form a +2 ion which most transition elements exhibit. The other charges arise from subsequent loss of 1 or more d electrons. s’s lost first, then d’s

Note that in the second cation, Fe 3+, The 3d subshell consists of 5 unpaired, same spin electrons, leading us next to a consideration of the topic of magnetism... But first: Group Work...

GROUP WORK Do: Short form, order of shells for atom, then for ion: Ag, Ag + I, I 1- Zn, Zn 2+ Se, Se 2-

Ag, Z=47: [Kr 36 ] 4d 10 5s 1 Ag 1+ : [Kr 36 ] 4d 10 Zn, Z=30: [Ar 18 ] 3d 10 4s 2 Zn 2+ : [Ar 18 ] 3d 10 I, Z=53: [Kr 36 ] 4d 10 5s 2 5p 5 I 1- : [Kr 36 ] 4d 10 5s 2 5p 6 Se, Z= 34: [Ar 18 ] 3d 10 4s 2 4p 4 Se 2- : [Ar 18 ] 3d 10 4s 2 4p 6 Key:

Magnetism Substances may be classified under this heading three ways: a) diamagnetic: slightly repelled by a strong magnet b) paramagnetic: attracted to a magnetic field, c) ferromagnetic: strongly attracted to magnetic field

Most substances fall into the category of “diamagnetic”, meaning that they appear to be un-attracted to ordinary “kitchen” magnets, are are actually slightly repelled by strong magnetic fields generated in the laboratory. A significant number of metals and compounds are attracted to strong magnetic fields in the lab although they are not attracted to weak magnets of the “refrigerator” variety: they are “paramagnetic.”

On the other hand, the compounds or metals exhibiting “ferromagnetism” are used to make up ordinary household magnets and are attracted to weak and strong magnetic fields. Examples of this type are the salt magnetite, Fe 3 O 4, and “Alnico” an alloy of Al, Ni and Co. The characteristic which separates compounds and elements into these categories turns out to be one that is predicted by electronic configurations: the presence or absence of unpaired electrons in the ion or the atom...

Diamagnetism: no unpaired electrons in atom or either ion of compound; Paramagnetism: one or more unpaired electron in atom or either ion of compound; Ferromagnetism: many unpaired electrons in atom or either ion of compound.

We find unpaired electrons in the metallic elements when subshells are unfinished: Metals in Column 1A,(s 1 ); 3A,(s 2 p 1 ) 4A (s 2 p 2 ), 5A,(s 2 p 3 ) are predictably paramagnetic, as well as the transition and inner transition metals, d and f subshell fillers. Nonmetallic elements, except oxygen, form polyatomic molecules with no unpaired e’s, all diamagnetic ). Most compounds have no unpaired electrons and are diamagnetic as well; they have been lost, gained or shared in the bonding process. The notable exceptions are the ions of the d block metals.

Transition elements have many unpaired electrons in both atoms and ions, and offer best structures for ferromagnetism:

Group Work Do orbital box diagram for last subshell to be filled for the following elements, then decide which are “diamagnetic” (not attracted to a magnet, no unpaired e’s) “paramagnetic” (unpaired e’s, attracted) Cs, Ca, Cu, C, Kr

Key: Cs, Ca, Cu Cs, Z=55: [Xe 54 ] 6s 1 6s 1 paramagnetic Ca, Z=20: [Ar 18 ]3s 2 3s 2 diamagnetic Cu, Z=29: [Ar 18 ] 3d 10 4s 1 4s 1 paramagnetic

Key: C, Kr C, Z=6: [He 2 ] 2s 2 2p2 2p 2 paramagnetic Kr, Z=36: [Kr 36 ] diamagnetic All e’s paired