1

Reactivity– When reacting, atoms collide so their outer-most electrons (valence electrons) interact

• Those electrons that are “seen” by another atom or molecule

– Valence electrons are the reacting electrons

– Some atoms gain electrons, while others lose them• metals are “born losers”

– always give up their electrons to become more stable (to end with a complete valence shell – a complete octet)

• non-metals acquire those electrons lost by the metal– take on electrons to become more stable (to fill up their orbitals and complete the octet)

2

Silver (Ag)

– In the 1s22s22p63s23p64s23d104p65s14d10 state• 1 valence electron to react

– Ag wants to lose the electron, emptying its 5s-sublevel– Becomes Ag+

» 47 protons but only 46 electrons

– The +1 ion is the most stable configuration that Ag can be in

3

Lead (Pb)– Pb has a partially filled and a completely filled sublevel as its valence shell

• 1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p2

• 1s22s22p63s23p63d104s24p64d104f145s25p65d106s26p2

– Pb wants to exist in the lowest energy state possible

• Pb loses 6p2 electrons to become Pb2+ ion - lead(II)– 1s22s22p63s23p63d104s24p64d104f145s25p65d106s2

• Pb loses 6s26p2 electrons to become Pb4+ ion – lead(IV)–1s22s22p63s23p63d104s24p64d104f145s25p65d10

Valence Electrons

4

Tin (Sn)

– Tin has very similar properties to lead, except that its most abundant state is Sn4+ - tin(IV)

• 1s22s22p63s23p64s23d104p65s24d105p2

• 1s22s22p63s23p63d104s24p64d105s25p2

• Lose 5s25p2 electrons to become Sn4+

• Lose just 5p2 electrons to become Sn2+

Valence Electrons

5

Bismuth (Bi) and Thallium (Tl)– Both bismuth and thallium exhibit similar reactivity

• Tl: 1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p1

– 1s22s22p63s23p63d104s24p64d104f145s25p65d106s26p1

• Tl can lose either the 6p1 or the 6s26p1 electrons to form a +1 or +3 species respectively

• Bi: 1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p3

– 1s22s22p63s23p63d104s24p64d104f145s25p65d106s26p3

• Bi can lose the 6p3 or the 6s26p3 electrons to form the +3 or +5 ions respectively

6

Halogens– The halogens have a similar desire for stability and lower energy, but it’s acquired differently

• Fluorine– 1s22s22p5 [He] 2s22p5

• Chlorine– 1s22s22p63s23p5 [Ne] 3s23p5

• Bromine– 1s22s22p63s23p64s23d104p5

– 1s22s22p63s23p63d104s24p5

– All halogens have a completely filled s-sublevel and are 1 electron from a full p-sublevel

• They can gain 1 electron to fill their p-sublevels– “Completing the octet”

What do you notice about the valence electrons?

7

Halogens– When the halogens gain an electron, they become -1 anions (F-, Cl-, Br-)

– In completing their octets, halogens become isoelectronic with the next element, the noble gas

• Two species are isoelectronic if they have the same electronic configurations

– F- is isoelectronic with Ne» 1s22s22p6

– Cl- is isoelectronic with Ar» 1s22s22p63s23p6

– Br- is isoelectronic with Kr» 1s22s22p63s23p64s23d104p6

8

To be isoelectronic …

– O2- is isoelectronic with Ne•1s22s22p6

– The same way that non-metals can be isoelectronic with the noble gases, metals can too

• Na+ (losing the 3s1 electron) is isoelectronic with Ne– 1s22s22p6 (complete octet is in the 2nd energy level)

• Sr2+ is isoelectronic with Kr– 1s22s22p63s23p64s23d104p6

• Fr+ is isoelectronic with Rn– 1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p6

9

Metals and Isoelectronic

– Some metals have similar (but not exact) electron configurations to other atoms when charged

– Zn can lose its 4s2 electrons, giving it the same valence configuration as Ar

• 1s22s22p63s23p63d104s2

• Zn has a full d-sublevel, whereas Ar does not– Zn2+: 1s22s22p63s23p63d10

– Ar: 1s22s22p63s23p6

• Zn is pseudo-isoelectronic with Ar

10

Isoelectronic or Pseudoisoelectronic?

– State whether the atoms are isoelectronic or pseudoisoelectronic with the indicated noble gases

• Na+ Ne• Ca2+ Ar• Cu+ Ar• I- Xe• Pd4+ Kr• Hf4+ Xe

Isoelectronic

Isoelectronic

Pseudo-isoelectronic

Isoelectronic

Pseudo-isoelectronic

Isoelectronic

11

Electronic Trends in the Periodic Table

Alkali Metals (Group 1)

– H 1s1

– Li 1s22s1

– Na 1s22s22p63s1

– K 1s22s22p63s23p64s1

– Rb 1s22s22p63s23p64s23d104p65s1

– Cs 1s22s22p63s23p64s23d104p65s24d105p66s1

– Fr 1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p67s1

12

Electronic Trends in the Periodic Table

Alkaline Earth Metals (Group 2)

– Be 1s22s2

– Mg 1s22s22p63s2

– Ca 1s22s22p63s23p64s2

– Sr 1s22s22p63s23p64s23d104p65s2

– Ba 1s22s22p63s23p64s23d104p65s24d105p66s2

– Ra 1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p67s2

13

Electronic Trends in the Periodic Table

Halogens (Group 17)

– F 1s22s22p5

– Cl 1s22s22p63s23p5

– Br 1s22s22p63s23p64s23d104p5

– I 1s22s22p63s23p64s23d104p65s24d105p5

– At 1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p5

14

Electronic Trends in the Periodic Table

Nobel Gases (Group 18)

– He 1s2

– Ne 1s22s22p6

– Ar 1s22s22p63s23p6

– Kr 1s22s22p63s23p64s23d104p6

– Xe 1s22s22p63s23p64s23d104p65s24d105p6

– Rn 1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p6