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docbasa2ptable2 updated April 18th 2008

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 Advanced Level Inorganic Chemistry Revision notes

(e.g. UK Advanced Level Chemistry GCE-AS-A2-IB US K12 grades ~11-12)

 The Periodic Table

 Part 2 "Electronic Structure and Ionisation Energies 1st draft

 Electron arrangements - electron configurations - ionization energy patterns

GCSE Atomic Structure Notes  *  GCSE Periodic Table notes  *  EMAIL query?comment

Part 2 Electronic structure & Ionization Energy page sub-index: 2.1 The modern Periodic Table * 2.2 The electronic structure of atoms (including s p d f subshells/orbitals/notation) * 2.3 Electron configurations of elements (Z = 1 to 56) * 2.4 Electron configuration and the Periodic Table * 2.5 Electron configuration of ions and oxidation states * 2.6 Spectroscopy and the hydrogen spectrum * 2.7 Evidence of quantum levels from ionisation energies

Advanced Periodic Table Index * Part 1 A brief Periodic Table history * the modern Periodic Table * Part 3 Period 1 survey : 1. Hydrogen : 2. Helium : Summary of  Period 1 : heavier element formation-stellar nuclear fusion * Part 7 s-block metals Gps 1/2 Alkali/Alkaline Earth Metals * Part 10 3d-block Sc-Zn and Transition MetalsPart 11 Group and Series data summaries and links to periodicity plots

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 2.1 The modern version of the Periodic Table is based on the electronic structure of atoms

  • With our knowledge of atomic structure the modern Periodic Table is now laid out in order of atomic/proton number (Z) and any apparent anomalies sorted out.

  • The atomic/proton number of the nucleus (Z) decides which element the atom is, the number of electrons surrounding the nucleus and hence the element's chemistry which is based on the number of electrons and their arrangement. The full Periodic Table (Z = 1 to 112) is shown further down the page with the element symbol, atomic/proton number (Z) and another version of the Periodic Table (Z = 1 to 56) showing the electron configuration which is explained in the next section 2.2.

    • In these notes the convention Z = atomic/proton number is used extensively.

  • Due to isotopic mass variations and their nuclear stability, the relative atomic mass does sometimes go 'up/down' as you proceed through the Periodic Table. See Part 1 Mendeleev's Periodic table work.

  • The use and function of the Periodic Table will never cease! Newly 'man-made' elements, beyond uranium (Z=92), are being 'synthesised' in nuclear reactors and cyclotrons. See GCSE nuclear reactions and radioactivity page. 

  • We now know the electronic structure of elements and can understand how the electrons are arranged in principal and sub-electronic levels and the 'quantum rules' of electron structure are understood.

  • This knowledge now allows us to understand why the Periodic Table makes sense in terms of the known chemistry of the elements, and their subsequent classification, prior to the discovery and understanding of the significance of the sub-atomic particles, particularly the proton and electron and their 'arrangement' in an atom.

  • Mendeleev and his contemporaries central ideas on classifying elements, despite some errors and omissions (i.e. not discovered), are now fully vindicated by our knowledge of the electronic structure of atoms. Mendeleev's powerful intuition on 'element patterns' was brought to full fruition by Rutherford and his contemporaries in discovering the secrets of the atom and quantum physicists elucidating the 'quantum patterns' of how multi-electron systems function.

  • For the simplified version of expressing electronic arrangements up to atomic number 20 and the relationship of the element in the Periodic Table, see the GCSE Atomic Structure Notes. Its not a bad idea to revise the basics before getting stuck into the advanced stuff!

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 2.2 The 'detailed' electronic structure of the atoms of the various elements

The details required by different pre-university syllabuses as regards background theory and orbital knowledge seems to vary quite a lot, so I've done by best to cater for all of them. If you wish to go straight to working out the s, p, d electron configuration of an element, click here!

  • How to use the advanced s, p, d (f) notation for the electron configuration/arrangement of atoms/ions is outlined below, but no knowledge of quantum mechanics is required, but you do need to know how to work out electron arrangements from the rules and a little knowledge of the shape of orbitals wouldn't go amiss! You do NOT need to know the origin of the rules or know all about the four quantum numbers, BUT I can't stand pulling rules out of a hat, so I have given a little theoretical introduction, if can't stand that, tough!

  • To accurately describe an electron in an atom requires four quantum numbers which arise from solutions to the elaborate mathematical equations of quantum mechanics, which describe the exceedingly complex wave behaviour of electrons.

    • These four quantum numbers arise from solutions to the complex equations which describe the wave and quantised behaviour of electrons surrounding the nucleus.

    • The first three quantum numbers have 0 or +/- integer values and the fourth one is +/- 1/2)

  • The Pauli exclusion principle states that no electron in an atom can have the same four quantum numbers, i.e. at least one must differ from electron to electron for a single atom.

  • The four quantum numbers are:

    1. The principal quantum energy level number n or shell (n = 1,2, 3 ...), often just referred to as 'the level'. It is important to think of this as the principal energy level, i.e. the principal quantum level an electron can occupy.

    2. The subsidiary/azimuthal/angular quantum number, l, this defines the 'spatial' type of sub-shell orbital, (l = 0 to n-1).  often just referred to as 'the sub-level or more specifically the s/p/d/f sub-level' (see orbital diagrams later). Again, it is important to think of this as a sub-energy level of an electron.

      • For s orbital (l = 0), p orbital (l = 1), d orbital (l = 2) diagrams below, and for the f orbital (l = 3).

      • For a given principal quantum number the order of energy of the sub-level is s < p < d < f.

    3. The magnetic or spatial orientation (of the orbital) quantum number, m, in terms of x,y,z axis (m = -l ... 0 ... l)

      • where l = the azimuthal quantum number 2. above and allows for each principal quantum level n, one s orbital for n = 1, 2, 3 etc., three p orbitals per for n = 2, 3, 4 etc., 5 d orbitals for n =3, 4, 5 etc. and seven orbitals for n = 4, 5, 6 etc.

      • See the orientation of the three p type orbitals and the five d type orbitals.

    4. The electron's spin, s, which has the value of +1/2 or -1/2 and can be envisaged as the electron spinning clockwise/anti-clockwise in a full individual orbital.

      • Electrons possess spin and if an orbital is filled then the pair of electrons must have opposite spins (spin-paired).

      • This due to Pauli exclusion principle, which states that no electron can have the same four quantum numbers, since the other three quantum numbers would be the same for a specific orbital, it is the spin quantum number which will differ (+/- 1/2).

  • The principal quantum electronic energy levels (n) can be split into sub-levels denoted by s, b, d and f depending on the number of electrons in the 'system'.

  • The 'space' in which the electron exists with its particular quantum level energy is called the atomic orbital and each type, s, p, d or f has its own particular 'shape' or 'shapes'.

  • Each individual atomic orbital can 'hold' a maximum of two electrons.

  • s, p and d orbital diagrams.

    • Diagram notes:

      1. The diagrams are NOT to scale and are simplified.

      2. These are from theoretical calculations based on the probability functions of the peculiar behaviour of electrons from the deep realms of quantum mechanics!

      3. These mathematical functions giving rise to an electron probability distribution e.g. illustrated by the pictures below of s, p and d orbitals.

      4. They only give a very approximate representation of electron density.

      5. Each orbital, that is the space a particular quantum level occupies, can hold a maximum of two electrons of opposite spin (+/- 1/2)

      6. Quantum physicists would say that these picture are not real, its all matrix mathematics really, BUT chemists like pictures, and pictures can often help students understand difficult concepts and most importantly, use the concepts to describe chemical systems and predict properties of atoms and molecules etc.

    • s atomic orbital

      • s orbitals have a spherical shell shape and the faint dark blue circle represents in cross-section, the region of maximum electron density.

      • Only one s orbital exists for each principal quantum number denoted by 1s, 2s, 3s etc.

    • *

    • p orbitals

      • p orbitals are pairs of 'dumb-bells' aligned along the x, y and z axis at 90o to each other.

      • There are three p orbitals for each principal quantum number from 2 onwards denoted by 2p, 3p and 4p etc.

        • e.g. 2p can be composed of 2px, 2py and 2pz if all three orbitals for a particular principal quantum number are occupied.

        • If a p sub-shell is full it holds a maximum of 3 x 2 = 6 electrons.

        • There is no 1p because quantum rules do not allow this.

    • *

    • d atomic orbitals

      • d orbitals have complex shapes, I say no more except their relative alignment is important in explaining the origin of colour in transition metal complexes.

      • There are five d  orbitals for each principal quantum number from 3 onwards denoted by 3d, 4d, 5d etc.

      • If a d sub-shell is full it contains a maximum of 5 x 2 = 10 electrons.

      • There are no 1d or 2d quantum levels, the quantum rules do not permit these.

    • f orbitals - orbital shapes not relevant at this level, the first is the 4f level and there are 7 orbitals holding a maximum of 7 x 2 = 14 electrons if the sub-shell is full.

  • Don't worry too much about all the 'quantum' details above, the important features to appreciate are described below.

  • To sum up 'numerically' from the quantum number rules, for the principal quantum number n ...

    • Each atomic orbital can hold a maximum of two electrons.

    • For each principal quantum level n, the following rules apply ...

    • for n = 1, there is just one sub-shell: 1s, maximum of 2 electrons,

    • for n = 2 there are two sub-shells: 1 x 2s atomic orbital and 3 x 2p orbitals, maximum of 2 + 6 = 8 electrons,

    • for n = 3 there are three sub-shells: 1 x 3s,3 x 3p orbitals and 5 x 3d orbitals, maximum of 2 + 6 + 10 = 18 electrons,

    • for n = 4 there are four sub-shells: 1 x 4s,3 x 4p orbitals, 5 x 4d orbitals and 7 x 4f orbitals, maximum of 2 + 6 + 10 + 14 = 32 electrons.

    • However the order of filling is not this simple (see below, with visual diagrammatic help).

  • The arrangement of electrons in the shells and orbitals is called the electronic configuration or electron arrangement/structure and is written out in a particular sequence.

  • The orbital electrons are denoted in the form of e.g. 2p3

    • means there are three electrons (super-script number 3)

    • in the p sub-shell (the lower case letter)

    • and in the second principal quantum level/shell (prefix number 2).

  • The quantum levels and associated orbitals are filled according to the Aufbau Principle which states that an electron goes into the lowest available energy level providing the following 'sub-rules' are obeyed.

    • The Pauli exclusion principle states that no two electrons can have the same four quantum numbers.

    • Hund's Rule of maximum multiplicity states that, as far as is possible, electrons will occupy orbitals so that they have parallel spins. This means if a set of sub-shell orbitals of the same energy level e.g. a 2p or 3d set, each orbital will be singly occupied before pairing (to minimise electron repulsion within a single atomic orbital, i.e. a lower energy state than paired electron orbitals and unoccupied orbitals.

  • The orbitals are filled in a definite order to produce the system of lowest energy and any electron will go into the lowest available energy level.

    • The order of 'filling' for an electron configuration is shown in the diagram below.

    • It uses is a simple diagrammatic convention to show an atomic orbital as a box.

    • Electrons are shown as half-arrows (up/down to represent the different spin quantum number s), see the 2nd diagram.

  • The order of filling (up to atomic number Z = 36, H to Kr)  is 1s 2s 2p 3s 3p 4s 3d 4p, up to a total 36 electrons from Z = 1 to 36 i.e. the order of increasing energy of the subshell or energy sub-level.

    • Note the 'quirk' in order for filling the 3d sub-shell energy level (see also the diagram below).

    • Until atomic number 21 (Sc) is reached, the 3d level is too high in energy and the electrons go into the 4s level and then the 3d level is filled from Sc to Zn.

    • This, and other 'quirks' I'm afraid, are a feature of the quantum complexity of multi-electron systems, so just learn the rules and get on with life!

  • After Z=30, the 'filling' of the 4p level begins with Ga (Z=31) to Kr (Z=36). After Z=36, and up to Z=56, so after 4p the filling order is, 5s 4d 5p 6s, thus completing period and starting period 6 (and also repeating the pattern of filling in period 4 including a 2nd block of metals, the 4d block.

    • The diagram for vanadium (Z=23), 1s22s22p63s23p63d34s2 is shown below.

    • *

    • Just a thought experiment do the following ...

      • 'Empty' the 3d level of electron arrows and you get the diagram for calcium (Z = 20).

      • Fill up completely the 3d and 4p boxes with arrows and you get krypton (Z = 36)

  • The table below shows how they are written out up to Z = 56 and a few others and note the orbital order when writing out.

  • They are written out in strict order of principal quantum number 1, 2, 3 etc. and each principal quantum number is followed by the s, p or d sub-levels  etc., and this is irrespective of the order of filling, i.e. when writing out the configuration, you ignore the 3d filling 'quirk' described above. 

  • Also in the table, some are written out in box diagram format, each box represents an orbital with a maximum of two electrons of opposite spin (shown by the opposing arrows). Note the electrons only pair up when all sub-orbitals are filled separately with a single electron (this minimises electron pair repulsion within an orbital).

  • Elements with one or two outer s electrons, and no outer p or d electrons etc., are called s-block elements (Groups 1 and 2).

  • Elements with at least one outer p electron are called p-block elements (Groups 3 to 8/0).

  • Elements where the highest available d sub-shell is being filled are called d-block elements (*Transition Metals) and similarly elements where the highest available f sub-shell is being filled are called f-block elements (the Lanthanides and Actinides).

    • * Sc-Zn is the 3d block, BUT true transition elements form at least one chemically stable ion with a partly filled sub-shell of d electrons.

      • Sc only forms Sc3+ [Ar]3d0, and Zn only forms Zn2+ [Ar]3d104s2, so the true 3d-block transition metals are Ti to Cu.

      • Can you spot the other electronic 'quirks' for chromium and copper?

      • Explanation: It would appear that a half-filled 3d subshell (Cr) or a full 3d sub-shell (Cu) is a tad more stable than a full 4s level.

  • Quantum theory dictates that electrons can only have certain specific 'quantised' energies and any electronic level change requires a specific energy change.

  • Any electron will occupy the lowest available energy level according to the Aufbau principle (previously described).

  • The order of 'filling' up to atomic number 56 from the lowest to highest quantum level is ...

    • 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s

  • Writing out electron configurations for atoms:

  • To work out an electron arrangement for an atom, you start with the atomic number, then 'fill in' the levels and sub-levels according to the rule.

    • The electron configuration is written out in order of, firstly, the principal quantum energy level, then within this level in s, p, d, f order and the total number of electrons in each sub-energy level is shown as a super-script.

  • Example 1. sodium, Na, Z = 11

  • 1s filled (2e) 9e left, 2s filled (2e) 7e left, 2p filled (6e) 1e left, last e goes into the 3s level. According to the notation rule this is written as ...

  • 1s22s22p63s1  (2.8.1 in simplified shell notation)

  • Example 2. vanadium, V, Z = 23

  • 1s filled (2e) 21e left, 2s filled (2e) 19e left, 2p filled (6e) 13e left, 3s filled (2e) 11e left, 3p filled (6e) 5e left, 4s filled (2e) 3e left, last 3e go into 3d level. According to the notation rule this is written as ...

  • 1s22s22p63s23p63d34s2  (2.8.11.2 in simplified shell notation)

  • Example 3. bromine, Br, Z = 35

  • Filling in the first 18e as described in example 2. will give an argon structure (1s22s22p63s23p6), which can be abbreviated to [Ar], the next 2e go into the 4s level (15e left), the next 10e go into the 3d level, the final 5e go into the 4p level.

  • [Ar]3d104s24p5  (2.8.18.7 in simplified notation) Note the use of 'noble gas notation' as an abbreviation for all the filled inner sub-shells making up the equivalent of noble gas electron arrangement, and will not include the 'outer electrons').

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 2.3 List of the Electronic Configuration of Elements 1 to 56 using the advanced notation

The rules of how to assign electrons in multi-electron atoms to the appropriate quantum levels is explained in section 2.2. The list below quotes the ground state electron configurations i.e. the lowest available state according to the Aufbau principle (previously described).

Electron Box diagrams of the outer electron arrangement and examples of the simple electron notation (e.g. 2.8.1) are also included, with brief comments in the end right hand column e.g. element symbol, group, series etc. The electrons-in-boxes notation for subshells: Boxes are used to represent an individual orbital or set of orbitals in the electrons are shown as arrows. The pairs up/down arrows represent a full orbital with electrons of opposite spin and note how the half-filled boxes/orbitals illustrate Hund's rule of maximum multiplicity.

The energy level filling order up to Z = 56 is 1s 2s 2p 3s 3p 4s 3d 4p (for Z = 1 to 36) 5s 4d 5p 6s 4f 5d (for Z = 37 to 56)

Atomic number Z and the element name and symbol

Electron configuration

Box diagram of outer electron orbitals (representing the superscripted electron numbers beyond the inner noble gas core in [He/Ne/Ar/Kr] which is never involved in chemical bonding/reactions)

Symbol, group/series/block and Comments

1 Hydrogen, H 1s1 1s H, no Gp really, a bit unique!
2 Helium, He 1s2 = [He] 2s He, Gp 0/18 Noble Gas,
3 Lithium, Li 1s22s1 (simple notation: 2.1) [He]2s2p Li, s-block, Gp1 Alkali Metal,
4 Beryllium, Be 1s22s2 (2.2) [He]2s2p Be, s-block, Gp2 Alkaline Earth Metal,
5 Boron, B 1s22s22p1 (2.3) [He]2s2p B, p-block, Gp3/13
6 Carbon, C 1s22s22p2 (2.4) [He]2s2p C, p-block, Gp4/14,
7 Nitrogen, N 1s22s22p3 (2.5) [He]2s2p N, p-block, Gp5/15,
8 Oxygen, O 1s22s22p4 (2.6) [He]2s2p O, p-block, Gp6/16,
9 Fluorine, F 1s22s22p5 (2.7) [He]2s2p F, p-block, Gp7/17 Halogen,
10 Neon, Ne 1s22s22p6 = [Ne] (2.8) [He]2s2p Ne, p-block, Gp 0/18 Noble Gas,
11 Sodium, Na 1s22s22p63s1 (2.8.1) [Ne]3s3p Na, Gp1 Alkali Metal,
12 Magnesium, Mg 1s22s22p63s2 (2.8.2) [Ne]3s3p Mg, s-block, Gp2 Alkaline Earth Metal,
13 Aluminium, Al 1s22s22p63s23p1 (2.8.3) [Ne]3s3p Al, p-block, Gp3/13,
14 Silicon, Si 1s22s22p63s23p2 (2.8.4) [Ne]3s3p Si, p-block, Gp4/14,
15 Phosphorus, P 1s22s22p63s23p3 (2.8.5) [Ne]3s3p P, p-block, Gp5/15,
16 Sulphur, S 1s22s22p63s23p4 (2.8.6) [Ne]3s3p S, p-block, Gp6/16,
17 Chlorine, Cl 1s22s22p63s23p5 (2.8.7) [Ne]3s3p Cl, p-block, Gp7/17 Halogen,
18 Argon, Ar 1s22s22p63s23p6 = [Ar] (2.8.8) [Ne]3s3p Ar, p-block, Gp 0/18 Noble Gas,
19 Potassium, K 1s22s22p63s23p64s1 (2.8.8.1) [Ar]3d4s4p K, s-block, Gp1 Alkali Metal,
20 Calcium, Ca 1s22s22p63s23p64s2 (2.8.8.1) [Ar]3d4s4p Ca, s-block, Gp2 Alkaline Earth Metal,
21 Scandium, Sc 1s22s22p63s23p63d14s2 [Ar]3d4s4p Sc, 3d block, not true Transition Metal
22 Titanium, Ti 1s22s22p63s23p63d24s2 [Ar]3d4s4p Ti, 3d block, a true Transition Metal
23 Vanadium, V 1s22s22p63s23p63d34s2 [Ar]3d4s4p V, 3d block, a true Transition Metal
24 Chromium, Cr 1s22s22p63s23p63d54s1 [Ar]3d4s4p Cr, 3d block, a true Transition Metal
25 Manganese, Mn 1s22s22p63s23p63d54s2 [Ar]3d4s4p Mn, 3d block, a true Transition Metal
26 Iron, Fe 1s22s22p63s23p63d64s2 [Ar]3d4s4p Fe, 3d block, a true Transition Metal
27 Cobalt, Co 1s22s22p63s23p63d74s2 [Ar]3d4s4p Co, 3d block, a true Transition Metal
28 Nickel, Ni 1s22s22p63s23p63d84s2 [Ar]3d4s4p Ni, 3d block, a true Transition Metal
29 Copper, Cu 1s22s22p63s23p63d104s1 [Ar]3d4s4p Cu, 3d block, a true Transition Metal
30 Zinc, Zn 1s22s22p63s23p63d104s2 [Ar]3d4s4p Zn, 3d block, not true Transition Metal
31 Gallium, Ga [Ar]3d104s24p1 [Ar]3d4s4p Ga, p-block, Gp3/13,
32 Germanium, Ge [Ar]3d104s24p2 [Ar]3d4s4p Ge, p-block, Gp4/14,
33 Arsenic, As [Ar]3d104s24p3 [Ar]3d4s4p As, p-block, Gp5/15,
34 Selenium, Se [Ar]3d104s24p4 [Ar]3d4s4p Se, p-block, Gp6/16,
35 Bromine, Br [Ar]3d104s24p5 [Ar]3d4s4p Br, p-block, Gp7/17 Halogen,
36 Krypton, Kr [Ar]3d104s24p6 = [Kr] [Ar]3d4s4p Kr, p-block, Gp 0/18 Noble Gas,
37 Rubidium, Rb [Kr]5s1 [Kr]5s Rb, s-block, Gp1 Alkali Metal,
38 Strontium, Sr [Kr]5s2 [Kr]5s Sr, s-block, Gp2 Alkaline Earth Metal,
39 Yttrium, Y [Kr]4d15s2 [Kr]4d5s Y, 4d block, not true Transition Metal
40 Zirconium, Zr [Kr]4d25s2 [Kr]4d5s Zr, 4d block, a true Transition Metal
41 Niobium, Nb [Kr]4d45s1 [Kr]4d5s Nb, 4d block, a true Transition Metal
42 Molybdenum, Mo [Kr]4d55s1 [Kr]4d5s Mo, 4d block, a true Transition Metal
43 Technetium, Tc [Kr]4d55s2 [Kr]4d5s Tc, 4d block, a true Transition Metal
44 Ruthenium, Ru [Kr]4d75s1 [Kr]4d5s Ru, 4d block, a true Transition Metal
45 Rhodium, Rh [Kr]4d85s1 [Kr]4d5s Rh, 4d block, a true Transition Metal
46 Palladium, Pd [Kr]4d10 [Kr]4d5s Pd, 4d block, a true Transition Metal
47 Silver, Ag [Kr]4d105s1 [Kr]4d5s5p Ag, 4d block, a true Transition Metal
48 Cadmium, Cd [Kr]4d105s2 [Kr]4d5s5p Cd, 4d block, not true Transition Metal
49 Indium, In [Kr]4d105s25p1 [Kr]4d5s5p In, p-block, Gp3/13,
50 Tin, Sn [Kr]4d105s25p2 [Kr]4d5s5p Sn, p-block, Gp4/14, 
51 Antimony, Sb [Kr]4d105s25p3 [Kr]4d5s5p Sb, p-block, Gp5/14,
52 Tellurium, Te [Kr]4d105s25p4 [Kr]4d5s5p Te, p-block, Gp6/16,
53 Iodine, I [Kr]4d105s25p5 [Kr]4d5s5p I, p-block, Gp7/17 Halogen,
54 Xenon, Xe [Kr]4d105s25p6 = [Xe] [Kr]4d5s5p Xe, p-block, Gp 0/18 Noble Gas,
55 Caesium, Cs [Xe]6s1 [Xe]6s Cs, s-block, Gp1 Alkali Metal,
56 Barium, Ba [Xe]6s1 [Xe]6s Ba, s-block, Gp2 Alkaline Earth Metal,
57 Lanthanum, La [Xe]5d16s2 [Xe]5d6s La, start of the Lanthanide metal series
58 Cerium, Ce [Xe]4f26s2 not 4f15d16s2  things get a bit less systematic in the f blocks Ce, 1st of f-block in the Lanthanides

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 2.4 Electron configuration and the Periodic Table

Pd s block 3d/4d blocks of Transition Metals (Periods 4/5), the 1st/10th are NOT true transition elements, they have no partially filled d shell in an ion. p block
Gp1 Gp2 Gp3 Gp4 Gp5 Gp6 Gp7 Gp0
1

1H 1s1

2He 1s2
2 3Li [He]2s1 4Be [He]2s2 The electronic structure of Elements 1 to 56, ZSymbol, Z = atomic or proton number = total electrons in neutral atom, [He] = 1s2, [Ne] = 1s22s22p6, [Ar] = 1s22s22p63s23p6, [Kr] = 1s22s22p63s23p63d104s24p6

Between Groups 2 and 3 (13) are the d-blocks and f-blocks where the quantum energy level rules permit their inclusion and electron filling. Periods 4 and 5 have 18 elements each, including the 3d and 4d blocks respectively.

5B [He]2s22p1 6C [He]2s22p2 7N [He]2s22p3 8O [He]2s22p4 9F [He]2s22p5 10Ne [He]2s22p6
3 11Na [Ne]3s1 12Mg [Ne]3s2 13Al [Ne]3s23p1 14Si [Ne]3s23p2 15P [Ne]3s23p3 16S [Ne]3s23p4 17Cl [Ne]3s23p5 18Ar [Ne]3s23p6
4 19K [Ar]4s1 20Ca [Ar]4s2 21Sc [Ar] 3d14s2 22Ti [Ar] 3d24s2 23V [Ar] 3d34s2 24Cr [Ar] 3d54s1 25Mn [Ar] 3d54s2 26Fe [Ar] 3d64s2 27Co [Ar] 3d74s2 28Ni [Ar] 3d84s2 29Cu [Ar] 3d104s1 30Zn [Ar] 3d104s2 31Ga [Ar] 3d104s24p1 32Ge [Ar] 3d104s24p2 33As [Ar] 3d104s24p3 34Se [Ar] 3d104s24p4 35Br [Ar] 3d104s24p5 36Kr [Ar] 3d104s24p6
5 37Rb [Kr]5s1 38Sr [Kr]5s2 39Y [Kr] 4d15s2 40Zr [Kr] 4d25s2 41Nb [Kr] 4d45s1 42Mo [Kr] 4d55s1 43Tc [Kr] 4d55s2 44Ru [Kr] 4d75s1 45Rh [Kr] 4d85s1 46Pd [Kr] 4d10 47Ag [Kr] 4d105s1 48Cd [Kr] 4d105s2 49In [Kr] 4d105s25p1 50Sn [Kr] 4d105s25p2 51Sb [Kr] 4d105s25p3 52Te [Kr] 4d105s25p4 53I [Kr] 4d105s25p5 54Xe [Kr] 4d105s25p6
6 55Cs [Xe]6s1 56Ba [Xe]6s2 4f-block (14) and 5d-block (10) 32 elements in period 6 including the Lanthanide Series of Metals. 81Tl [Xe] 5d106s26p1 82Pb [Xe] 5d106s26p2 83Bi [Xe] 5d106s26p3 84Po [Xe] 5d106s26p4 85At [Xe] 5d106s26p5 86Rn [Xe] 5d106s26p6
7 87Fr [Rn]7s1 88Ra [Rn]7s2 5f-block and 6d-block including the Actinide Series of Metals.            
  • Note: Using 0 to denote the Group number of Noble Gases is very historic now since compounds of xenon known exhibiting a valency of 8. Because of the horizontal series of elements e.g. like the Sc to Zn block (10 elements), Groups 3 to 0('8 ') can also be numbered as Groups 13 to 18 to fit in with the actual number of vertical columns of elements. This can make things confusing, but there it is, classification is still in progress! The atomic/proton number, decides which element an atom is and the outer electron structure decides which group/block/series the element belongs to and ultimately its chemistry.

    • The s p d f blocks are shown in the Periodic Table above.

  • Groups of elements:

    • The vertical 'group' connection of similar outer electron configuration is consistent except for V/Nb, Fe/Ru, Co/Rh, Ni/Pd where the 3d/4s and 4d/5s pairs of levels are of very similar energy and small differences in outer electron configuration occur.

  • Blocks of elements:

    • The s-block consists of Groups 1 and 2 where the only outer electrons are in an s sub-energy level orbital.

    • The p-block correspond to Groups 3 to 8 where the three p sub-energy level orbitals are being filled.

    • Starting with period 4, where the first of the d sub-shells is low enough in energy to be filled, there are ten elements 'inserted' between groups 2 and 3, the so-called 3d block. Similarly on period 5 there is a 4d block where the 4d sub-shell level is filled.

    • Starting with cerium (Z=58, period 6), see in full table below, there is a further insertion of fourteen elements where the seven f-orbital sub-shell is being filled after the first of the d-block metals and similarly with thorium (Z=90) in period 7.

  • Series of elements:

    • The 1st Transition Metals and other 'horizontal blocks' are sometimes called a 'series' but they are better described as the '3d block' or '3d series of elements' The reference to the electronic structure is very important, the word series is a bit vague! Technically, scandium (Sc, Z = 21) and zinc (Zn, Z = 30), are NOT true transition metals BUT they are true 3d block elements! (for more details see ???? working on!)

  • The full Periodic Table is shown below.

Pd s block 3d to 6d blocks of Transition Metals (Periods 4 to 7), note that the 1st (d1) and 10th (d10) are NOT true transition elements. p block
Gp1 Gp2 Gp3 Gp4 Gp5 Gp6 Gp7 Gp0
1

1H   Note: (i) H does not readily fit into any group, (ii) He not strictly a 'p' element but does belong in Gp 0/8

2He
2 3Li 4Be The full IUPAC modern Periodic Table of Elements (ZSymbol, z = atomic or proton number) 5B 6C 7N 8O 9F 10Ne
3 11Na 12Mg 13Al 14Si 15P 16S 17Cl 18Ar
4 19K 20Ca 21Sc 22Ti 23V 24Cr 25Mn 26Fe 27Co 28Ni 29Cu 30Zn 31Ga 32Ge 33As 34Se 35Br 36Kr
5 37Rb 38Sr 39Y 40Zr 41Nb 42Mo 43Tc 44Ru 45