Periodic Table (Chemistry Reference)

Chemistry-focused element reference: electron shells, valence behaviour, oxidation states and common laboratory constants.

Search this reference

Where the standard periodic table answers "what is this element?", a chemistry reference answers "how will it react?". This page groups the elements by the properties that matter at the bench — valence electrons, common oxidation states, electronegativity trends and shell structure — and adds the constants and conventions you need when balancing equations or preparing solutions.

Group properties and valence behaviour

Group	Name	Valence electrons	Common oxidation states	Reactivity trend
1	Alkali metals	1	+1	Increases down the group
2	Alkaline earth metals	2	+2	Increases down the group
3–12	Transition metals	2 (plus d-electrons)	+2, +3, +4, +6, +7	Varies; multiple stable states
13	Boron group	3	+3 (also +1 for Tl)	Metallic character increases down
14	Carbon group	4	+4, +2, −4	Nonmetal to metal down the group
15	Nitrogen group (pnictogens)	5	−3, +3, +5	Nonmetal to metal down the group
16	Oxygen group (chalcogens)	6	−2, +4, +6	Decreases down the group
17	Halogens	7	−1, +1, +3, +5, +7	Decreases down the group
18	Noble gases	8 (2 for He)	0	Essentially inert

9 rows

Electron shell capacity

Shell	Principal quantum number n	Subshells	Maximum electrons
K	1	1s	2
L	2	2s, 2p	8
M	3	3s, 3p, 3d	18
N	4	4s, 4p, 4d, 4f	32
O	5	5s, 5p, 5d, 5f	32 (occupied)
P	6	6s, 6p, 6d	18 (occupied)
Q	7	7s, 7p	8 (occupied)

7 rows

Common elements: symbol, mass and state

The forty most frequently used elements in general chemistry, pulled from the full 118-element list.

Z	Symbol	Element	Atomic mass (u)	Family	State at 20 °C
1	H	Hydrogen	1.008	Reactive nonmetal	Gas
2	He	Helium	4.0026	Noble gas	Gas
3	Li	Lithium	6.94	Alkali metal	Solid
4	Be	Beryllium	9.0122	Alkaline earth metal	Solid
5	B	Boron	10.81	Metalloid	Solid
6	C	Carbon	12.011	Reactive nonmetal	Solid
7	N	Nitrogen	14.007	Reactive nonmetal	Gas
8	O	Oxygen	15.999	Reactive nonmetal	Gas
9	F	Fluorine	18.998	Reactive nonmetal	Gas
10	Ne	Neon	20.180	Noble gas	Gas
11	Na	Sodium	22.990	Alkali metal	Solid
12	Mg	Magnesium	24.305	Alkaline earth metal	Solid
13	Al	Aluminium	26.982	Post-transition metal	Solid
14	Si	Silicon	28.085	Metalloid	Solid
15	P	Phosphorus	30.974	Reactive nonmetal	Solid
16	S	Sulfur	32.06	Reactive nonmetal	Solid
17	Cl	Chlorine	35.45	Reactive nonmetal	Gas
18	Ar	Argon	39.95	Noble gas	Gas
19	K	Potassium	39.098	Alkali metal	Solid
20	Ca	Calcium	40.078	Alkaline earth metal	Solid
21	Sc	Scandium	44.956	Transition metal	Solid
22	Ti	Titanium	47.867	Transition metal	Solid
23	V	Vanadium	50.942	Transition metal	Solid
24	Cr	Chromium	51.996	Transition metal	Solid
25	Mn	Manganese	54.938	Transition metal	Solid
26	Fe	Iron	55.845	Transition metal	Solid
27	Co	Cobalt	58.933	Transition metal	Solid
28	Ni	Nickel	58.693	Transition metal	Solid
29	Cu	Copper	63.546	Transition metal	Solid
30	Zn	Zinc	65.38	Transition metal	Solid
31	Ga	Gallium	69.723	Post-transition metal	Solid
32	Ge	Germanium	72.630	Metalloid	Solid
33	As	Arsenic	74.922	Metalloid	Solid
34	Se	Selenium	78.971	Reactive nonmetal	Solid
35	Br	Bromine	79.904	Reactive nonmetal	Liquid
36	Kr	Krypton	83.798	Noble gas	Gas
37	Rb	Rubidium	85.468	Alkali metal	Solid
38	Sr	Strontium	87.62	Alkaline earth metal	Solid
39	Y	Yttrium	88.906	Transition metal	Solid
40	Zr	Zirconium	91.224	Transition metal	Solid

40 rows

Key chemistry constants

Constant	Symbol	Value	Unit
Avogadro constant	N_A	6.02214076 × 10²³	mol⁻¹
Molar gas constant	R	8.314462618	J mol⁻¹ K⁻¹
Molar volume of ideal gas (STP, 0 °C, 100 kPa)	V_m	22.711	L mol⁻¹
Faraday constant	F	96485.332	C mol⁻¹
Standard atmosphere	atm	101325	Pa
Boltzmann constant	k_B	1.380649 × 10⁻²³	J K⁻¹
Elementary charge	e	1.602176634 × 10⁻¹⁹	C
Ion product of water at 25 °C	K_w	1.0 × 10⁻¹⁴	—

8 rows

Diatomic and polyatomic elements

Element	Natural form	Notes
Hydrogen	H₂	Diatomic gas; lightest element
Nitrogen	N₂	Diatomic; triple bond makes it very stable
Oxygen	O₂ (also O₃)	Diatomic gas; ozone is the triatomic allotrope
Fluorine	F₂	Most electronegative element
Chlorine	Cl₂	Diatomic yellow-green gas
Bromine	Br₂	Diatomic liquid at room temperature
Iodine	I₂	Diatomic solid that sublimes readily
Phosphorus	P₄	Tetratomic in white phosphorus
Sulfur	S₈	Puckered eight-membered ring at room temperature

9 rows

From atomic number to molar mass

Each element is defined by its atomic number, the count of protons in an atom of that element. The atomic weight in the table is also the molar mass in g/mol, so 1 mol of carbon, 12.011 in the table, has a mass of about 12.011 g. The mole itself is defined in the SI units table.

About the Periodic Table (Chemistry)

Sources

Classification: Standard atomic data + educational chemistry reference

Sources

IUPAC — Standard Atomic Weights and element data
International Union of Pure and Applied Chemistry

Electron shells, valence behaviour and common oxidation states are compiled from standard chemistry references. Oxidation states shown are the common states; many elements exhibit additional rare states. Laboratory constants are standard reference values. The table is an educational chemistry reference, not a complete spectroscopic dataset.

How it was compiled

Electron-shell configuration follows the Aufbau principle; valence behaviour is inferred from the outer-shell electrons. Common oxidation states reflect the typical loss/gain/sharing of valence electrons in compounds. The table complements the main periodic table with chemistry-focused detail.

How current it is

Classification: Stable (educational reference)

Electron configurations and common oxidation states are stable. Atomic weights are refined periodically by IUPAC; the values shown are current conventional weights.

Limitations

Common oxidation states are the typical ones; many elements have additional rare states not listed.
Electron-shell notation is the ground-state configuration; excited states and anomalous configurations exist.
Laboratory constants are reference values; confirm precise values from a current chemistry handbook for critical work.

Using it

Use the table for chemistry education and quick reference; use a full handbook for complete oxidation-state and spectroscopic data.
Treat listed oxidation states as common, not exhaustive.
For reaction balancing, confirm the relevant oxidation state for the specific compound.

Units and notation

Atomic number dimensionless; atomic weight in unified atomic mass units (u); oxidation states as signed integers.

Frequently Asked Questions

How is this different from the Periodic Table of Elements page?

The elements page is the complete 118-element data table. This page focuses on reaction chemistry: valence electrons, oxidation states, shell capacities, diatomic forms and the constants used in stoichiometry.

What are valence electrons?

Valence electrons are the electrons in the outermost shell. They determine bonding behaviour, and elements in the same group share the same valence count.

Why do transition metals have several oxidation states?

Their d-orbital electrons are close in energy to the outer s electrons, so different numbers of electrons can be removed at comparable energy cost.

What is the difference between STP and standard ambient conditions?

STP as defined by IUPAC is 0 °C and 100 kPa, giving a molar volume of 22.711 L/mol. Standard ambient temperature and pressure (SATP) is 25 °C and 100 kPa, giving 24.79 L/mol.

How do I use the Avogadro constant?

Multiply the number of moles by 6.022 × 10²³ to get the number of particles, or divide a particle count by it to get moles.

Which elements exist as diatomic molecules?

Hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine and iodine occur naturally as diatomic molecules.

Explore Knowledge

Go deeper with FlowUtil guides that explain the concepts behind this reference table.

Browse Knowledge Library