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Introduction to the periodic table

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Introduction to the Periodic Table

The periodic table is an organized chart of all the chemical elements. Learn how it is organized by atomic number into periods (rows) and groups (columns), how to read an element's box (symbol, atomic number, atomic mass), and the metal, nonmetal and metalloid regions.

What the periodic table is

The periodic table is an organized chart of all the known chemical elements — the pure substances that everything is made of, like hydrogen, oxygen, and gold. It is not just a list: the table arranges the elements so that their positions reveal their properties. Learning to read it is one of the most useful skills in chemistry.

Three ideas explain the whole layout:

  • Atomic number order. Elements are placed in order of their atomic number — the number of protons in the atom — increasing from left to right and top to bottom.
  • Periods (rows). Each horizontal row is a period. There are seven periods.
  • Groups (columns). Each vertical column is a group, or family. Elements in the same group have similar chemical properties, which is what makes the table so powerful for making predictions.
How the periodic table is organized A periodic table showing the atomic number in each box, increasing left to right and top to bottom. Each row is a period (1 to 7) and each column is a group (1 to 18); one group column and one period row are highlighted. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 1 2 3 4 5 6 7 Groups (columns) 1 to 18 Periods (rows) 1 to 7 a group a period
How the periodic table is organized: elements are ordered by atomic number, each row is a period, and each column is a group.
Reading an element on the periodic table 6CCarbon12.01 atomic number symbol name atomic mass
Reading an element on the periodic table: atomic number, symbol, name, and atomic mass.

Every element has its own box showing four things: the atomic number (protons), the one- or two-letter symbol, the name, and the atomic mass. Those symbols are the same ones you use when you write chemical formulae.

The table is also split into broad regions. Most elements are metals (on the left and center) — shiny and good conductors. Nonmetals sit on the upper right. A narrow staircase of metalloids runs between them, with properties of both.

Periodic table: metals, nonmetals, and metalloids A periodic table with the three categories shaded: metals fill the left and center, nonmetals are in the upper right, and metalloids (boron, silicon, germanium, arsenic, antimony, tellurium, polonium) run along the staircase that separates them. H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og * * La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr MetalsNonmetalsMetalloids
The periodic table shaded by category: metals, nonmetals, and metalloids.

Because position predicts behavior, the periodic table lets you estimate an element's properties just from where it sits. Working with the very large and very small numbers in chemistry is easier with scientific notation, another core intro skill.

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