Periodic table
The periodic table of the elements
The following figure shows the currently known periodic table of the elements.
Each element is listed by its atomic number and chemical symbol. Elements in the same column ("group") are chemically similar.
| Group | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | ||
| Period | ||||||||||||||||||||
| 1 | 1 H |
2 He |
||||||||||||||||||
| 2 | 3 Li |
4 Be |
5 B |
6 C |
7 N |
8 O |
9 F |
10 Ne |
||||||||||||
| 3 | 11 Na |
12 Mg |
13 Al |
14 Si |
15 P |
16 S |
17 Cl |
18 Ar |
||||||||||||
| 4 | 19 K |
20 Ca |
21 Sc |
22 Ti |
23 V |
24 Cr |
25 Mn |
26 Fe |
27 Co |
28 Ni |
29 Cu |
30 Zn |
31 Ga |
32 Ge |
33 As |
34 Se |
35 Br |
36 Kr |
||
| 5 | 37 Rb |
38 Sr |
39 Y |
40 Zr |
41 Nb |
42 Mo |
43 Tc |
44 Ru |
45 Rh |
46 Pd |
47 Ag |
48 Cd |
49 In |
50 Sn |
51 Sb |
52 Te |
53 I |
54 Xe |
||
| 6 | 55 Cs |
56 Ba |
* |
71 Lu |
72 Hf |
73 Ta |
74 W |
75 Re |
76 Os |
77 Ir |
78 Pt |
79 Au |
80 Hg |
81 Tl |
82 Pb |
83 Bi |
84 Po |
85 At |
86 Rn |
|
| 7 | 87 Fr |
88 Ra |
* * |
103 Lr |
104 Rf |
105 Db |
106 Sg |
107 Bh |
108 Hs |
109 Mt |
110 Ds |
111 Uuu |
112 Uub |
113 Uut |
114 Uuq |
115 Uup |
116 Uuh |
117 Uus |
118 Uuo |
|
| * Lanthanides | 57 La |
58 Ce |
59 Pr |
60 Nd |
61 Pm |
62 Sm |
63 Eu |
64 Gd |
65 Tb |
66 Dy |
67 Ho |
68 Er |
69 Tm |
70 Yb |
||||||
| ** Actinides | 89 Ac |
90 Th |
91 Pa |
92 U |
93 Np |
94 Pu |
95 Am |
96 Cm |
97 Bk |
98 Cf |
99 Es |
100 Fm |
101 Md |
102 No |
||||||
| Alkali metals | Alkaline earths | Lanthanide | Actinides | Transition metals |
| Poor metals | Metalloids | Nonmetals | Halogens | Noble gases |
Color coding for atomic numbers:
- Elements numbered in blue are liquids at room temperature;
- those in green are gases at room temperature;
- those in black are solid at room temperature;
- those in red are synthetic and do not occur naturally (all are solid at room temperature).
- those in gray have not yet been discovered (they also have muted fill colors indicating the likely chemical series they would fall under).
Other methods for displaying the chemical elements
- Standard Table
- Alternate Table
- Anti table
- Big Table
- Huge Table
- Wide Table
- Extended Table
- Table in Chinese
- Electron Configurations
- Metals and Non Metals
- Periodic table filled by blocks
- List of elements by name
- List of elements by symbol
- List of elements by atomic number
- List of elements by boiling point
- List of elements by melting point
- List of elements by density
- List of elements by atomic mass
The number of electron shells an atom has determines what period it belongs to. Each shell is divided into different subshells, which as atomic number increases are filled in roughly this order:
Explanation of the structure of the periodic table
1s
2s 2p
3s 3p
4s 3d 4p
5s 4d 5p
6s 4f 5d 6p
7s 5f 6d 7p
8s 5g 6f 7d 8p
...
Hence the structure of the table. Since the outermost electrons determine chemical properties, those tend to be similar within groups. Elements adjacent to one another within a group have similar physical properties, despite their significant differences in mass. Elements adjacent to one another within a period have similar mass but different properties.
For example, very near to nitrogen (N) in the second period of the chart are carbon (C) and oxygen (O). Despite their similarities in mass (they differ by only a few atomic mass units), they have extremely different properties, as can be seen by looking at their allotropes: diatomic oxygen is a gas that supports burning, diatomic nitrogen is a gas that does not support burning, and carbon is a solid which can be burnt (yes, diamonds can be burnt!).
In contrast, very near to chlorine (Cl) in the next-to-last group in the chart (the halogens) are fluorine (F) and bromine (Br). Despite their dramatic differences in mass within the group, their allotropes have very similar properties: They are all highly corrosive (meaning they combine readily with metals to form metal halide salts); chlorine and fluorine are gases, while bromine is a very low-boiling liquid; chlorine and bromine at least are highly colored.
History
The original table was created without a knowledge of the inner structure of atoms: if one orders the elements by atomic mass, and then plots certain other properties against atomic mass, one sees an undulation or periodicity to these properties as a function of atomic mass.
The first to recognize these regularities was the German chemist Johann Wolfgang DÃÂöbereiner who, in 1829, noticed a number of triads of similar elements:
| Some triads | ||
|---|---|---|
| Element | Atomic mass | Density |
| chlorine | 35.5 | 0.00156 g/cm3 |
| bromine | 79.9 | 0.00312 g/cm3 |
| iodine | 126.9 | 0.00495 g/cm3 |
| calcium | 40.1 | 1.55 g/cm3 |
| strontium | 87.6 | 2.6 g/cm3 |
| barium | 137 | 3.5 g/cm3 |
This was followed by the English chemist John Alexander Reina Newlands, who in 1865 noticed that the elements of similar type recurred at intervals of eight, which he likened to the octaves of music, though his law of octaves was ridiculed by his contemporaries. Finally, in 1869, the German Lothar Meyer and the Russian chemist Dmitry Ivanovich Mendeleev almost simultaneously developed the first periodic table, arranging the elements by mass. However, Mendeleev plotted a few elements out of strict mass sequence in order to make a better match to the properties of their neighbours in the table, corrected mistakes in the values of several atomic masses, and predicted the existence and properties of a few new elements in the empty cells of his table. Mendeleev was later vindicated by the discovery of the electronic structure of the elements in the late 19th and early 20th century.
See also
Further resources
External links
| Chemistry |
| Analytical chemistry | Organic chemistry | Inorganic chemistry | Biochemistry | Physical chemistry |
| Periodic table |