12 3456789 101112 131415161718
iAiiA iiiBivBvBviB viiBviiiB iBiiB iiiAivAvAviA viiAviiiA
K H
1
Periodic Table of the Elements He
2
L Li
3
Be
4
 Antoine Lavoisier 
 (1743-1794)  Dimitri Mendeleev 
 (1834-1907)  Wide Periodic Table
Transition Metals   ( B )
B
5
C
6
N
7
O
8
F
9
Ne
10
M Na
11
Mg
12
Al
13
Si
14
P
15
S
16
Cl
17
Ar
18
N K
19
Ca
20
Sc
21
Ti
22
V
23
Cr
24
Mn
25
Fe
26
Co
27
Ni
28
Cu
29
Zn
30
Ga
31
Ge
32
As
33
Se
34
Br
35
Kr
36
O Rb
37
Sr
38
Y
39
Zr
40
Nb
41
Mo
42
Tc
43
Ru
44
Rh
45
Pd
46
Ag
47
Cd
48
In
49
Sn
50
Sb
51
Te
52
I
53
Xe
54
P Cs
55
Ba
56
La Hf
72
Ta
73
W
74
Re
75
Os
76
Ir
77
Pt
78
Au
79
Hg
80
Tl
81
Pb
82
Bi
83
Po
84
At
85
Rn
86
Q Fr
87
Ra
88
Ac Rf
104
Db
105
Sg
106
Bh
107
Hs
108
Mt
109
Ds
110
Rg
111
Cn
112
Nh
113
Fl
114
Mc
115
Lv
116
Ts
117
Og
118
Lanthanides: La
57
Ce
58
Pr
59
Nd
60
Pm
61
Sm
62
Eu
63
Gd
64
Tb
65
Dy
66
Ho
67
Er
68
Tm
69
Yb
70
Lu
71
Actinides: Ac
89
Th
90
Pa
91
U
92
Np
93
Pu
94
Am
95
Cm
96
Bk
97
Cf
98
Es
99
Fm
100
Md
101
No
102
Lr
103

Alphabetically :

Actinium (89)
Aluminium (13, UK)
Aluminum (13, US)
Americium (95)
Antimony (51)
Argon (18)
Arsenic (33)
Astatine (85)
Barium (56)
Berkelium (97)
Berylium (4)
Bismuth (83)
Bohrium (107)
Boron (5)
Bromine (35)
Cadmium (48)
Caesium (55, UK)
Calcium (20)
Californium (98)
Carbon (6)
Cerium (58)
Cesium (55, US)
Chlorine (17)
Chromium (24)
Cobalt (27)
Copernicium (112)
Copper (29)
Curium (96)
Darmstatium (110)
Dubnium (105)
Dysprosium (66)
Einsteinium (99)
Erbium (68)
Europium (63)
Fermium (100)
Flerovium (114)
Fluorine (9)
Francium (87)
Gadolinium (64)
Gallium (31)
Germanium (32)
Gold (79)
Hafnium (72)
Hassium (108)
Helium (2)
Holmium (67)
Hydrogen (1)
Indium (49)
Iodine (53)
Iridium (77)
Iron (26)
Krypton (36)
Lanthanum (57)
Lawrencium (103)
Lead (82)
Lithium (3)
Livermorium (116)
Lutetium (71)
Magnesium (12)
Manganese (25)
Meitnerium (109)
Mendelevium (101)
Mercury (80)
Molybdenum (42)
Moscovium (115)
Neodymium (60)
Neon (10)
Neptunium (93)
Nickel (28)
Nihonium (113)
Niobium (41)
Nitrogen (7)
Nobelium (102)
Oganesson (118)
Osmium (76)
Oxygen (8)
Palladium (46)
Phosphorus (15)
Platinum (78)
Plutonium (94)
Polonium (84)
Potassium (19)
Praseodymium (59)
Promethium (61)
Protactinium (91)
Radium (88)
Radon (86)
Rhenium (75)
Rhodium (45)
Roentgenium (111)
Rubidium (37)
Ruthenium (44)
Rutherfordium (104)
Samarium (62)
Scandium (21)
Seaborgium (106)
Selenium (34)
Silicon (14)
Silver (47)
Sodium (11)
Strontium (38)
Sulfur (16)
Sulphur (16)
Tantalum (73)
Technetium (43)
Tellurium (52)
Tennessine (117)
Terbium (65)
Thallium (81)
Thorium (90)
Thulium (69)
Tin (50)
Titanium (22)
Tungsten (74)
Uranium (92)
Vanadium (23)
Xenon (54)
Ytterbium (70)
Yttrium (39)
Zinc (30)
Zirconium (40)

 
 Axel Fredrik Cronstedt  
 1722-1765 
 Nickel, 1751
 Mueller von reichenstein 
 1742-1825 
 Tellurium, 1783
 Johan Gadolin 
 1760-1852 
 Yttrium, 1792
 Nicolas Vauquelin 
 1763-1829 
 Chromium, 1797 
 Berylium, 1798
 William Hyde Wollaston 
 1766-1828
 Palladium, 1803 
 Rhodium, 1804
 Hans Christian Oersted 
 1777-1851
 Aluminium, 1825
 Humphry Davy 
 1778-1829 
 Sodium, 1807 
 Potassium, 1807 
 Magnesium, 1808
 Calcium, 1808 
 Strontium, 1808
 Barium, 1808
 Lecoq de Boisbaudran 
 1838-1912 
 Gallium, 1875 
 Samarium, 1880 
 Dysprosium, 1886
 Marie Curie 
 1867-1934 
 Polonium and Radium, in 1896
 Dubna 
 founded in 1956
 Dubnium, 1994
 

Chemical Elements

Chemical elements are uniquely characterized by their  atomic numbers  (Z)  (now defined as the number of protons in a nucleus of that element).

Before  Mendeleev (1834-1907)  made that notion clear with an early version of the above table,  in 1869,  many basic facts puzzled chemists.  They could only work with  mass numbers  obtained by measuring the weight ratios of low-pressure gases, using  Avogadro's law (1811).  Mass-numbers can be useful to identify elements but they don't provide reliable clues to guess the relations between them.  They are only  approximately  integers and they do not always increase with Z...

For example, Scheele (1742-1786)  had discovered,  in 1774,  that muriatic acid was composed of hydrogen and something else, which he guessed to be an oxide of some new element with  mass number  19.45,  tentatively dubbed "muriaticum"  (the prejudice of that era,  formulated by Lavoisier in 1777,  was that all acids should contain oxygen).

Disproving Lavoisier's preconceptions and Scheele's guess, Humphry Davy (1778-1829)  showed,  in 1810,  that "muriaticum" doesn't exist.  The "oxide of muriaticum" discovered by Scheele was actually a new  element  (Cl = Chlorine, of mass 35.45).

The reason why mass-numbers are close to integers for many important elements but not for some others, including chlorine, wasn't understood until the notion of  isotope  emerged, in 1913.

The great confusion of a bygone era is entirely resolved by the  periodic table of elements  whose structure is worth comitting to memory:

A PG-rated French mnemonic   (about a  weird  family diner)    Just a joke!
KHo He!
LLili Becta Bien Chez Notre Oncle François-Nestor.
M   Napoléon Mangea Allègrement Six Poulets Sans Clamser Après.  
NKarl Carrément Scanda :  "Tirez-Vous, Craignez
Mon roce Courroux...  Nichée Cupide, Zinzins teux,
rontes Assurément niles, Brigands Kremlinesques."
ORebecca Strangula Yvon Zircon...
Nébuleuses Motivations  (Techniquement, "Rut Rhénan", Pardi)
Agitant Cadavéreusement,  Indéniablement,
Son Subconscient Tellement Idéologiquement Xénophobe.

For the Lanthanides  (elements 57-71)  see Martyn Poliakoff's video on Lanthanum:
Language Centers Praise Ned's Promise of Small European Garden Tubs.
Dinosaurs Hobble Erotically Thrumming Yellow Lutes
.
("Thrumming" is for thullium.  Yellow is for ytterbium.)

An easier American mnemonic for the Lanthanides (elements 57-71) is:
Ladies Can't Put Nickels Properly [into] Slot-machines.
Every Girl Tries Daily, However, Every Time You Look
.

  Main Classification :

H
1
Li
3
Na
11
K
19
Rb
37
Cs
55
Fr
87
Be
4
Mg
12
Ca
20
Sr
38
Ba
56
Ra
88
Sc
21
Y
39
La Ac
68 elements:
21-30, 39-48, 57-80, 89-112
O
8
S
16
Se
34
Te
52
Po
84
F
9
Cl
17
Br
35
I
53
At
85
He
2
Ne
10
Ar
18
Kr
36
Xe
54
Rn
86
  Hydrogen & Alkali Metals
First column.  Valence +1.  
Alkaline-Earth Metals 
Second column.  Valence +2.  
Rare Earths   (32 elements) 
Third column, including lanthanides and actinides.  
Transition Metals 
3rd to 12th column  (B columns)  including rare earths.  
Chalcogens 
Column 16.  Valence -2.  
Halogens 
Next-to-last column (17).  Valence -1.  
Noble Gases 
Last column (18).  Monoatomic gases.

The above grouping by column is supplemented by the important distinctions listed below.

Early textbooks (before the 1950's) were excluding groups 11 and 12 from the transition metals.  Elements of group 11 are now universally recognized as transition metals, so are elements of group 12 under the simple convention adopted here, following many modern authors who view  d-block  and  transition metals  as strictly synonymous.  The current definition from the IUPAC is controversial; it would classify Zinc and Cadmium as post-transition metals while Mercury  (and Copernicium)  should be considered transition metals, because of the recent (2007) synthesis of mercury tetrafluoride  (introducing a new oxidation state for Mercury that has been given a relativistic explanation which doesn't apply to Zinc or Cadmium).

Actinides are normally classified as  rare earths  because of their obvious chemical similarities with lanthanides, without the endorsement of the IUPAC  (this issue is relatively unimportant, because of the lack of chemical uses of actinides outside of nuclear engineering).

H
1
C
6
N
7
O
8
P
15
S
16
Se
34
  Hydrogen & Non-Metals   (7 non-metallic elements)
All non-metallic elements besides metalloids, halogens and noble gases. 
B
5
Si
14
Ge
32
As
33
Sb
51
Te
52
Po
84
  Metalloids   (7 elements with  some  metallic properties)
The  diagonal  between non-metals (above) and metals.
Al
13
Ga
31
In
49
Sn
50
Tl
81
Pb
82
Bi
83
  Post-transition Metals   (7 stable metals, several unstable ones)
Located below the metalloid diagonal.  (Some authors include Zn and Cd).
 
Lanthanides
57 - 71
  Lanthanides  (15 rare earths)
Elements whose last electron is  not  on the valence orbital.
Actinides
89 - 103
  Actinides  (15 rare earths)
Radioactive elements whose last electron is  not  on the valence orbital.
 
Rf
104
Db
105
Sg
106
Bh
107
Hs
108
Mt
109
Ds
110
Rg
111
Cn
112
...
  Transactinides
Unstable elements beyond actinides.

Obsolete or Deprecated Names and Symbols   [ video  |  Wikipedia ]
ZSymbolNameNotes:
18AArgonCurrent symbol is Ar.
41CbColumbiumHatchett's proposal (1801) for Niobium (Nb) deprecated in 1950.
(pelopium, ilmenium & dianium were mixtures with tantalum)
43MaMasuriumDisputed discovery (1925) of Technetium (Tc) by Noddack & al.
61FlFlorentiumDiscredited discovery (1924-26) of Promethium (Pm).
IlIlliniumAnother discredited discovery (1926) of Promethium.
62SaSamariumCurrent symbol is Sm.
70SpSpectriumRejected suggestion for Ytterbium (Yb).
71LuCassiopeiumAuer von Welsbach's proposal (1907) for Lutetium (Lu).
74WWolframOfficial name has been  tungsten  since 1950.
85AbAlabamineDiscredited discovery of Astatine (As) by Fred Allison (1931).
DoDorErroneous discovery (1939) by Horia Hulubei.
HvHelvetiumDisputed claim (1940) by Walter Minder.
87 Vi, Vm VirginiumFalse claim by Fred Allison (1930) for Francium (Perey, 1939).
MlMoldaviumAnother discredited claim (1936) for Francium (Fr) by Hulubei.
93SqSequanium Erroneous claim (1939) for Neptunium (Np) by Hulubei.
103LwLawrenciumCurrent symbol is Lr.
104KuKurchatoviumRussian claim for Rutherfordium (Rf).
105HaHahniumAmerican claim for Dubnium (Db).
NsNielsbohriumRussian proposal for Dubnium (Db).
JlJoliotiumObsolete IUPAC 1994 proposal for Dubnium (Db).
112CpCopernicumInitial proposal for Copernicium (Cn) by its discoverers (GSI).

As the above table demonstrates, the franctic search for elements 85 and 87  (before WWII)  once left a few nomenclature debris.  It also left at least one textbook example of  pathological science  (perceived observations at the threshold of detectability that turn into pseudoscience).  The so-called  (imaginary)  Allisson effect  was advocated by  Fred C. Allison (1882-1974)  well beyond the call of scientific duty, even after his method was disproved by H.G. MacPherson  (of UC Berkeley)  in 1934...  A case worth studying.

The current official procedures for enacting the names of new elements were adopted well after the settlement (1997) of a major naming controversy  (the Transfermium War)  about elements 104, 105 and 106.

In 1997, element 109  (Meitnerium, Mt) was named after  Lise Meitner  (1878-1968).  The rare honor was widely perceived has some kind of posthumus apology for not having shared the Nobel prize  (Chemistry 1944)  awarded to  Otto Hahn  for their joint work.  This was also a way to honor the  Hahn/Meitner  team, as the name  Hahnium  (for element 105)  had to be permanently dropped to avoid further confusion after the  naming war.

On 19 February 2010  (the 537 th anniversary of Copernicus' birth)  element 112 was officially given the name that had been under review since July 2009Copernicium  (Cn).  Its temporary name in the IUPAC system was Ununbium (Uub).  Alternately, it can be identified as eka-mercury (or eka-hydrargyrum, eka-Hg) the same way element 111  (Roentgenium, Rg)  was formerly known as eka-gold.  Mendeleev himself introduced the prefix "eka-" to name any undiscovered element after whatever appears above it in the periodic table  (such elements are chemically similar).

On 31 May 2012  elements 114 and 116 were officially named Flerovium and Livermorium, respectively.  Those names had been under review since December 2011.

On 12 August 2012, a Japanese team at RIKEN  (Rikagaku Kenkyujo  =  Institute for physical and chemical research)  has published their observation of a decay chain of an atom of Uut-278, including the well-known alpha-decay of  Db-262  into  Lr-258  which clearly identifies element 113 as the source of that decay chain.  This is construed as a definite discovery of 113, for which more ambiguous results had been obtained at RIKEN in 2004 and 2005  (and also at Livermore and Dubna between 2003 and 2005).  It's widely expected that the 2012 results will give naming rights to the Japanese, who had mentioned four possible names for element 113  (Japonium, Rikenium or Nishinarium).  Since March 2016, most bets seem to be on  Nipponium  (symbol Np).

On 2015-12-30,  the  IUPAC  has announced that they have completed their final review of the discovery claims for elements  113, 115, 117 and 118 and found them to be satisfactory.  The  IUPAC  is now inviting the respective teams of discovers to propose names and symbols for the new elements.  The scientific community at large will then be given a chance to offer comments before the names are finalized before the end of 2016.  This milestone is heralded at the  completion  of the periodic table  (or, at least, its  first seven lines,  up to and including the soon-to-be-properly-named element 118).  If nothing else, that's important for typographical and aesthetic reasons!

On 2016-06-08, the next-to-last step took the form of a  press release by the IUPAC announcing the four proposed names and the opening of a public discussion about them, scheduled to end in November 2016.

  • 113 :   (Nh)  Nihonium.  Country of Japan.
  • 115 :   (Mc)  Moscovium.  Town of Moscow.
  • 117 :   (Ts)  Tennessine.  US State of Tennessee.
  • 118 :   (Og)  Oganesson.  Yuri T. Oganessian (1933-).

Electronic Configurations :

The quantum state of an electron around a nucleus is fully described in terms of the following four  quantum numbers :

  • The principal quantum number (n) determines the  shell.  In the absence of external fields, the  (negative)  energy  of a bound electron depends  only  on that number  (it's inversely proportional to  n). 
  • The azimuthal quantum number (l) ranges from 0 to n-1 within a given shell and determines what's called a  subshell, normally designated by a traditional letter s (l=0), p (l=1), d (l=2) or f (l=3).
       
    Electrons per Subshell
    SubshellMaximum
     s  0 2
    p16
    d210
    f314
     L2(2L+1)
    The etymology of these letters can be traced to the spectroscopic vocabulary predating quantum mechanics (s=sharp, p=principal, d=diffuse, f=fundamental).  A subshell is normally denoted by the number of the shell (n) followed by such a letter, yielding a designation like  ns, np, nd or nf  (e.g., "3d"). 
  • The magnetic quantum number (m) ranges from -L to L within a given subshell and determines an  orbital, which may "contain" no more than two electrons of opposite  spins  (see next). 
  • The spin of an electron is a two-valued quantum number (s = ±½).

The  Pauli Exclusion Principle  states that two electrons cannot be in the same quantum state.  They must differ in at least one of the values of the above 4 quantum numbers.  This implies that a subshell (n,l) may contain no more than 2(2l+1) electrons, as tabulated above  (the total number within the whole shell is at most 2n).

1s
2s          2p
3s          3p
4s      3d  4p
5s      4d  5p
6s  4f  5d  6p
7s  5f  6d  7p
   

The minimal energy of the electronic cloud surrounding a lone nucleus is achieved when electrons occupy available subshell room in the order at left, starting with the 1s subshell.  This simplified version of the  Aufbau principle  explains the structure of the periodic table of elements, where elements with similar chemical properties are listed in the same column:  The chemical properties of an element depend mostly on the  valence  electrons located in the outermost subshell(s) which are usually the least favored energetically  (with the reservations noted below, in the case of "f" subshells).

The electronic configuration around a nucleus may be summarized by listing all nonempty subshells in the above order of increasing energies (1s, 2s, 2p, 3s, etc.) with a superscript indicating the number of electrons in each.  The repartition of electrons into orbitals of the same subshell is usually ignored.

A complementary term symbol is sometimes added to better describe the ground configuration.  It may be obtained using Hund's Rule,  a set of empirical recipes due to Friedrich Hund (1896-1997).  Electrons avoid pairing up on the same orbital unless all the orbitals of the subshell are occupied.

For brevity, the configuration of a noble gas may be denoted by its bracketed symbol  [as a prefix]  in the electronic configuration of subsequent elements.  Note that all subshells of noble gases are full.  Chemical inertness is due to an outter shell containing a total of 8 electrons (except for helium).

Electronic Configurations of the Noble Gases
 Electronic ConfigurationAlso Denoted:
He1s2  
Ne1s2 2s2 2p6 [He] 2s2 2p6
Ar1s2 2s2 2p6 3s2 3p6 [Ne] 3s2 3p6
Kr1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 [Ar] 4s2 3d10 4p6
Xe1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6     [Kr] 5s2 4d10 5p6
Rn1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f 14 5d10 6p6

In the periodic table, successive "transition metals" correspond to the "filling" of a "d" subshell (from 1 to 10 electrons).  Adding 1 to 14 electrons to the empty "f" subshell of Lanthanum yields the other elements of the Lanthanide series (Z = 58 to 71) whose chemical similarity with Lanthanum may be explained by stating that the "f" subshell corresponds to orbitals that are "closer" to the nucleus than those of the previous "s" subshell, so "f" electrons are less likely fo be valence electrons  (the same situation repeats with Actinium and the Actinides series, from Z = 89 to 103).  This geometrical explanation should not be taken too literally...

For completeness, it should be noted that the energy levels of some subshells are so close that the pairing of electrons may lead to a few exceptions  (in particular for Cr and Cu)  in the application of the simplified  Aufbau principle  presented above.

Geometric Designations of the Orbitals
  N     L   M
-2-10+1+2
10    1s   
20    2s   
1   2py 2pz 2px  
30    3s   
1   3py 3pz 3px  
2   3d xy   3d yz 3d z2 3d xz 3d x2-y2

Theoretically, the chemistry of even highly radioactive heavy elements can be precisely computed from the well-known laws of quantum electrodynamics  (as if  radioactivity didn't exist).  In practice, such a computation is way beyond our current abilities and chemistry remains an experimental science...  Nevertheless, the ingenuity of experimentalists is considerable and some chemical facts have been obtained for an element like Hassium (Z = 108) although only about 40 atoms of it have ever been observed.  This is made possible by the fact that Hassium happens to have a surprisingly stable isotope  (Hs-277)  with a half-life of more than  10 minutes,  as explained in an excellent video interview of Martyn Poliakoff  (part of  The Periodic Table of Videos,  produced by  Brady Haran).


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