Labeled Periodic Table: Groups, Periods and Blocks
A labeled periodic table arranges the 118 elements in 18 vertical groups and 7 horizontal periods, in order of atomic number. Groups share the same number of outer electrons, periods show the number of electron shells, and colours or labels mark families such as alkali metals, halogens and noble gases.
What are the parts of the periodic table?
The parts of the periodic table are easiest to learn as a short list:
- Element box: one square holding the symbol, name, atomic number and atomic mass.
- Group: a vertical column, numbered 1 to 18 from left to right.
- Period: a horizontal row, numbered 1 to 7 from top to bottom.
- Block: a region named after the type of orbital being filled (s, p, d or f).
- Family: a named group of similar elements, such as the halogens.
- Metal, metalloid and nonmetal zones: separated by a staircase line on the right.
All 118 known elements are placed by atomic number, the number of protons in the nucleus. Dmitri Mendeleev built the first version in 1869 by atomic mass, and Henry Moseley later showed in 1913 that atomic number is the true order.
How to read the periodic table: the element box
Take carbon as an example. Its box shows four things:
- C, the chemical symbol (the name is often written under it).
- 6, the atomic number: carbon has 6 protons, and 6 electrons when neutral.
- 12.011, the relative atomic mass: the average mass of carbon atoms, allowing for isotopes.
- The colour or label, which tells you carbon is a nonmetal.
Sodium reads Na, 11, 22.990. Iron reads Fe, 26, 55.845. If you want to see how isotopes change that decimal, read what is an isotope.
What are groups and periods?
A group is a column. Elements in the same group have the same number of outer (valence) electrons, so they react in similar ways. Group 1 elements all have one outer electron, and group 17 elements all have seven.
A period is a row. The period number equals the number of occupied electron shells. Sodium (period 3) has three shells with 2, 8 and 1 electrons, so it is in period 3 and group 1.
The periods are not all the same length: they hold 2, 8, 8, 18, 18, 32 and 32 elements. To go deeper on outer electrons, see how to find valence electrons.
Element families on the labeled periodic table
| Family | Where | Key facts | Examples |
|---|---|---|---|
| Alkali metals | Group 1 (not hydrogen) | Soft, very reactive, form +1 ions | Li, Na, K |
| Alkaline earth metals | Group 2 | Reactive, form +2 ions | Mg, Ca |
| Transition metals | Groups 3–12 | Hard, dense, coloured compounds | Fe, Cu, Au |
| Halogens | Group 17 | Reactive nonmetals, form −1 ions | F, Cl, Br, I |
| Noble gases | Group 18 | Full outer shell, almost unreactive | He, Ne, Ar |
| Metalloids | Staircase line | Properties between metals and nonmetals | B, Si, Ge, As, Sb, Te |
| Lanthanides and actinides | Two rows below | Elements 57–71 and 89–103 | La, U |
Hydrogen sits above group 1 but is a nonmetal, which surprises many students.
What are the s, p, d and f blocks?
The blocks show which type of orbital the last electron enters. The s-block is groups 1 and 2 (plus helium), the p-block is groups 13 to 18, the d-block is the transition metals, and the f-block is the lanthanides and actinides. The block tells you the shape of the electron configuration, which you can practise with how to find electron configuration.
Where are metals, nonmetals and metalloids?
A diagonal staircase from boron down to astatine separates the table. Metals are to the left, nonmetals to the right, and the elements touching the staircase are the metalloids. Two elements are liquid at room temperature: mercury (a metal) and bromine (a nonmetal).
Common mistakes
- Reading the decimal number as the atomic number. The whole number is the atomic number, and the decimal is the atomic mass.
- Mixing up groups and periods. Groups are columns, periods are rows.
- Forgetting that hydrogen is a nonmetal even though it sits in group 1.
- Counting the lanthanides and actinides as a separate part. They belong in periods 6 and 7.
Frequently asked questions
What are the labels on a periodic table?
A labeled periodic table shows group numbers 1–18, period numbers 1–7, element families (alkali metals, halogens, noble gases and so on), blocks (s, p, d, f) and the split between metals, metalloids and nonmetals. Each element box also gives the symbol, atomic number and atomic mass.
How many groups and periods are in the periodic table?
There are 18 groups (columns) and 7 periods (rows). Together they hold 118 confirmed elements, from hydrogen (atomic number 1) to oganesson (atomic number 118).
Why are the lanthanides and actinides separate?
They belong in periods 6 and 7, between groups 2 and 3. Putting them in line would make the table 32 columns wide, so they are pulled out and placed in two rows below the main table to keep it compact.
How do you find the number of valence electrons from the table?
For the main groups, the valence electron count is the last digit of the group number: group 1 has 1, group 2 has 2, group 13 has 3, and group 17 has 7. Group 18 has 8, except helium, which has 2.
Try it yourself
Open the interactive Periodic Table, click an element such as carbon or sodium, and find its group, period and block. Then compare the table's colours to the families above, and read the periodic table trends to see how properties change across a period.
See it for yourself, in 3D and free.
Try it in the Interactive Periodic Table