Reactive nonmetalElement 6 · p-block

Carbon (C)

Carbon (C) is a reactive nonmetal with atomic number 6 and a standard atomic weight of 12.011. At room temperature it is a solid that sublimes at 3,642 °C.

6CCarbon12.011

Atomic number

protons

Atomic weight

12.011

CIAAW 2024

Melting point

—

Boiling point

3,642 °C

sublimes (graphite) at 1 atm

Density

2.2 g/cm³

near room temperature

Electronegativity

2.55

Pauling scale

State at 25 °C

Solid

Discovered

Prehistoric

Carbon at a glance

Identity

Symbol	C
Atomic number (Z)	6
Atomic weight	12.011 ± 0.002 (CIAAW 2024)
Category	Reactive nonmetal
Group	14 — carbon group
Period	2
Block	p-block
CAS number	7440-44-0

Atomic properties

Electron configuration	[He] 2s² 2p² Full: 1s² 2s² 2p²
Electrons per shell	2, 4
Oxidation states	-4, +4 Less common: -3, -2, -1, 0, +1, +2, +3
Electronegativity (Pauling)	2.55
First ionisation energy	11.26 eV (1,086.5 kJ/mol) 2nd: 24.383 eV · 3rd: 47.888 eV
Electron affinity	1.262 eV
Atomic radius (empirical)	70 pm
Covalent radius	75 pm
Van der Waals radius	170 pm

Physical properties

State at 25 °C	Solid
Boiling / sublimation point	3,641.8 °C · 6,587.3 °F · 3,915 K sublimes (graphite) at 1 atm
Density	2.2 g/cm³
Specific heat capacity	0.709 J/(g·K)
Thermal conductivity	1.59 W/(m·K)
Crystal structure	Diamond cubic

Isotopes & abundance

Natural occurrence	Primordial
Radioactive	No
Natural isotopes (abundance)	¹²C 98.94%, ¹³C 1.06%
Stable isotopes	4
Known isotopes	16
Abundance in Earth's crust	200 mg/kg
Abundance in seawater	28 mg/L

Atomic weights: CIAAW Abridged Standard Atomic Weights 2024. Other properties: standard reference compilations, checked October 2026; predicted values are marked.

Carbon electron configuration

Carbon has 6 electrons. Written in short form, its ground-state configuration is [He] 2s² 2p² — the electrons of the noble gas helium, plus 2s² 2p².Written out in full: 1s² 2s² 2p².

As a member of group 14 it has 4 valence electrons in its outer shell (shell 2), which largely decide its chemistry.

2s↑↓

2p↑↑

Discovery and name

Discovered

Prehistoric — Known since antiquity (as charcoal and soot).

Name

Latin carbo, charcoal.

Known for

The basis of all known life and of organic chemistry. It exists as graphite, diamond, graphene and fullerenes, and as carbon dioxide drives the greenhouse effect.

Isotopes of carbon

Naturally occurring carbon is a mix of 2 isotopes. Each has 6 protons; they differ in the number of neutrons:

Isotope	Protons	Neutrons	Natural abundance	Stability
¹²C	6	6	98.94%	stable
¹³C	6	7	1.06%	stable

16 isotopes of carbon are known in our data set (half-lives as published in nuclear data tables).

Carbon compared with group 14

The other elements in group 14 (carbon group), from top to bottom of the table:

Element	Z	Atomic weight	Melting point	Boiling point	Density	Electronegativity
Carbon	6	12.011	—	3,642 °C	2.2 g/cm³	2.55
Silicon	14	28.085	1,414 °C	3,265 °C	2.33 g/cm³	1.9
Germanium	32	72.630	938 °C	2,833 °C	5.323 g/cm³	2.01
Tin	50	118.71	232 °C	2,586 °C	7.287 g/cm³	1.96
Lead	82	207.2	327 °C	1,749 °C	11.3 g/cm³	2.33
Flerovium	114	[290]	—	—	9.928 g/cm³ (pred.)	—

Frequently asked questions

6 answers

What is the atomic mass of carbon?

The standard atomic weight of carbon is 12.011 ± 0.002 (CIAAW 2024), so one mole weighs about 12.011 grams.

How many protons, neutrons and electrons does carbon have?

A neutral carbon atom has 6 protons and 6 electrons. Its most common isotope, carbon-12, has 6 neutrons.

What is the electron configuration of carbon?

[He] 2s² 2p² (in full: 1s² 2s² 2p²).

What are the melting and boiling points of carbon?

Carbon sublimes at 3,641.85 °C (6,587.3 °F).

Is carbon a metal?

Carbon is a nonmetal. It is in group 14, period 2, and is a solid at room temperature.

Who discovered carbon?

Carbon has been known since ancient times.