Periodic Table - Layout

Layout

For a larger version, see Periodic table (large version).

Periodic table
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	*	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	**	104 Rf	105 Db	106 Sg	107 Bh	108 Hs	109 Mt	110 Ds	111 Rg	112 Cn	113 Uut	114 Fl	115 Uup	116 Lv	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	71 Lu
** 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	103 Lr
This is an 18-column periodic table layout, which has come to be referred to as the common or standard form, on account of its popularity. It is also sometimes referred to as the long form, in comparison to the short form or Mendeleev-style, which omits groups 3–12 by placing their elements into the main groups. The wide periodic table incorporates the lanthanides and the actinides, rather than separating them from the main body of the table. The extended periodic table adds the 8th and 9th periods, including the superactinides.
Some element categories in the periodic table Metals Metalloids Nonmetals Unknown chemical properties Alkali metals Alkaline earth metals Inner transition metals Transition metals Post-transition metals Other nonmetals Halogens Noble gases Lanthanides Actinides Color of the atomic number shows state of matter (at standard conditions: 0 °C and 1 atm): black=Solid green=Liquid red=Gas grey=Unknown Border shows natural occurrence: Primordial From decay Synthetic

All versions of the periodic table include only chemical elements, not mixtures, compounds, or subatomic particles. Each chemical element has a unique atomic number representing the number of protons in its nucleus. Most elements have differing numbers of neutrons among different atoms, with these variants being referred to as isotopes. For example, carbon has three naturally occurring isotopes: all of its atoms have six protons and most have six neutrons as well, but about one per cent have seven neutrons, and a very small fraction have eight neutrons. Isotopes are never separated in the periodic table; they are always grouped together under a single element. Elements with no stable isotopes have the atomic masses of their most stable isotopes, where such masses are shown, listed in parentheses.

In the standard periodic table, the elements are listed in order of increasing atomic number (the number of protons in the nucleus of an atom). A new row (period) is started when a new electron shell has its first electron. Columns (groups) are determined by the electron configuration of the atom; elements with the same number of electrons in a particular subshell fall into the same columns (e.g. oxygen and selenium are in the same column because they both have four electrons in the outermost p-subshell). Elements with similar chemical properties generally fall into the same group in the periodic table, although in the f-block, and to some respect in the d-block, the elements in the same period tend to have similar properties, as well. Thus, it is relatively easy to predict the chemical properties of an element if one knows the properties of the elements around it.

As of 2012, the periodic table contains 118 confirmed chemical elements. Of these elements, 114 have been officially recognized and named by the International Union of Pure and Applied Chemistry (IUPAC). A total of 98 of these occur naturally, of which 84 are primordial. The other 16 elements only occur in decay chains of primordial elements. All elements from einsteinium to copernicium, as well as flerovium and livermorium, while not occurring naturally in the universe, have been duly synthesized and officially recognized by the IUPAC. Elements 113, 115, 117 and 118 have reportedly been synthesized in laboratories but these reports have not yet been confirmed. As such these elements are currently known only by their systematic element names, based on their atomic numbers. No element heavier than einsteinium (element 99) has ever been observed in macroscopic quantities in its pure form. No elements past 118 have been synthesized as of 2012.