Presentation on theme: "Shape of orbitals s-orbitalp-orbitals. Electrons can only occupy so-called atomic orbitals with well defined energy levels corresponding to the principal."— Presentation transcript:
Shape of orbitals s-orbitalp-orbitals
Electrons can only occupy so-called atomic orbitals with well defined energy levels corresponding to the principal quantum number, n. The lowest level will have n = 1, the next n = 2, and so on. Electrons must always enter the first available orbital of lowest energy. The first element, hydrogen, only has one electron, and so this electron must enter the 1s orbital. The electronic configuration of hydrogen in the ground state must therefore be: H 1s 1.
Boron 1s 2 2s 2 2p 1 Atomic number 5 Carbon 1s 2 2s 2 2p 2 Atomic number 6 According to Hund’s rule, fill a set of similar energy orbitals with as many unpaired electrons as possible (as in the p or d orbitals).
The successive ionization energies of sodium [Ar] 3s 1 One electron furthest away from nucleus easiest to remove (3S 1 ) Eight nearer to nucleus, harder to remove (2p 6, 2p 2 ) Two very close to the nucleus and most difficult to remove (1s 2 ) Proves numbers of electrons in each shell is 2,8,1 Electron removed Ionization energy/KJmol -1 orbital 1st4963s1 2nd4565 3rd691 4th9544 5th th th th th th s 2 11th s 1 2p 6, 2p 2
First ionisation energies (IE) of elements in periods 2 to 4/KJmol -1 IEs increase across period (nuclear charge increasing, shielding the same) Li, 520 Be, 900 B, 801 C, 1086 N, 1402 O, 1314 F, 1681 Ne, 2081 Na, 495 Mg, 735 Al, 580 Si, 780 P, 1060 S, 1005 Cl, 1255 Ar, 1527 K, 419 Ca, 590 Ga, 579 Ge, 762 As, 947 Se, 941 Br, 1140 Kr, 1351 IEs decrease down a group (distance of outer electrons from nucleus increasing)
First ionisation energies (IE) of elements in periods 2 to 4/KJmol -1 1.Look at group II and group III: the first electron for Al is a 3P 1 electron and is less tightly held than 3S electron as it is further away from nucleus 2.Look at group V and group VI: a paired electron is easier to remove than an unpaired electron and the configuration for sulfur is 3P 4, so it has a paired electron Li, 520 Be, 900 B, 801 C, 1086 N, 1402 O, 1314 F, 1681 Ne, 2081 Na, 495 Mg, 735 Al, 580 Si, 780 P, 1060 S, 1005 Cl, 1255 Ar, 1527 K, 419 Ca, 590 Ga, 579 Ge, 762 As, 947 Se, 941 Br, 1140 Kr, 1351
The Ionization Energies for elements in Period 3 ElementI1I2I3I4I5I6I7 configuration Na [Ne]3S 1 Mg [Ne]3S 2 Al [Ne]3S 2 3P 1 Si [Ne]3S 2 3P 2 P [Ne]3S 2 3P 3 S [Ne]3S 2 3P 4 Cl [Ne]3S 2 3P 5 Ar [Ne]3S 2 3P 6 I1 = first ionization energy; A(g) A + (g) + e - I2 = second ionization energy; A + (g) A 2+ (g) + e - I3 etc.