Question 1

How many elements are in the periodic table?

Accepted Answer

The periodic table contains 118 confirmed elements, from hydrogen (atomic number 1) to oganesson (atomic number 118). The last four — nihonium, moscovium, tennessine and oganesson — were officially named by IUPAC in 2016. No element beyond 118 has been confirmed yet.

Question 2

Who created the periodic table?

Accepted Answer

Russian chemist Dmitri Mendeleev published the first widely recognised periodic table in 1869. He arranged the 63 elements known at the time by atomic mass and chemical behaviour, and left gaps for undiscovered elements — correctly predicting the properties of gallium, scandium and germanium. The modern table is ordered by atomic number, following Henry Moseley's work in 1913.

Question 3

What is the difference between a group and a period?

Accepted Answer

A group is a vertical column — there are 18. Elements in the same group have the same number of outer (valence) electrons, so they behave similarly: group 1 holds the reactive alkali metals and group 18 the unreactive noble gases. A period is a horizontal row — there are 7. Each period starts filling a new electron shell.

Question 4

What do atomic number and atomic mass mean?

Accepted Answer

The atomic number (Z) is the number of protons in the nucleus; it defines the element. The atomic mass is the weighted average mass of an element's naturally occurring isotopes, in atomic mass units (u), which is why it is rarely a whole number. For radioactive elements without stable isotopes, the mass number of the longest-lived isotope is shown in square brackets.

Question 5

What are the element categories?

Accepted Answer

Elements are grouped by shared properties into alkali metals, alkaline earth metals, transition metals, post-transition metals, metalloids, reactive nonmetals, halogens, noble gases, lanthanides and actinides. Click a category chip above the table to highlight its members, or open a category page for a full explanation.

Question 6

Which elements are liquid at room temperature?

Accepted Answer

Only two elements are liquid at standard room temperature (25 °C): mercury (a metal) and bromine (a nonmetal). Caesium (28.5 °C), gallium (29.8 °C) and rubidium (39.3 °C) melt just above room temperature. Use the Phase tab and drag the temperature slider to see every element change state.

Question 7

What is the lightest and the heaviest element?

Accepted Answer

Hydrogen is the lightest element (1.008 u). Oganesson (element 118) is the heaviest known element. The densest naturally occurring element is osmium (about 22.6 g/cm³), closely followed by iridium.

Question 8

Why are the lanthanides and actinides shown below the table?

Accepted Answer

The lanthanides (57–71) and actinides (89–103) belong in periods 6 and 7 between groups 2 and 3. Putting them in line would make the table 32 columns wide, so by convention they are shown as two separate rows underneath to keep it compact.

Question 9

What is electronegativity and how does it change across the table?

Accepted Answer

Electronegativity is an atom's pull on the electrons in a chemical bond, usually measured on the Pauling scale. It increases from left to right across a period and decreases down a group. Fluorine is the most electronegative element (3.98); caesium and francium are among the least. Choose Electronegativity in the Trends tab to see it as a heat map.

Question 10

How do atomic radius and ionization energy trend?

Accepted Answer

Atomic radius gets larger down a group, as each row adds a new electron shell, and smaller across a period, as the growing nuclear charge pulls electrons closer. First ionization energy — the energy needed to remove the outermost electron — follows the opposite pattern: highest for the noble gases at the top right and lowest for the alkali metals at the bottom left.

Question 11

What are valence electrons?

Accepted Answer

Valence electrons are the electrons in an atom's outermost shell, and they decide how an element bonds. For main-group elements the count follows the group: group 1 has one, group 2 has two, and groups 13 to 18 have three to eight. That is why elements in the same group react in similar ways.

Question 12

How do I read an electron configuration?

Accepted Answer

An electron configuration lists the orbitals an atom's electrons occupy, such as 1s² 2s² 2p⁶ for neon. The number is the shell, the letter (s, p, d, f) is the subshell and the superscript is how many electrons it holds. Configurations are often shortened with the previous noble gas in square brackets, so sodium becomes [Ne] 3s¹.

Question 13

Can I print this periodic table or save it as a PDF?

Accepted Answer

Yes. Press the Print button above the table: it switches to a clean, black-on-white A4 landscape layout with every element's number, symbol, name and your chosen value (for example atomic mass or electronegativity). Choose 'Save as PDF' in the print dialog to keep a copy.

Question 14

How does the temperature (phase) slider work?

Accepted Answer

Drag the slider from 0 K to 6000 K, or tap a preset such as room temperature or the surface of the Sun. Every element is coloured by whether it is solid, liquid or gas at that temperature, based on its melting and boiling points. You can switch units between kelvin, Celsius and Fahrenheit.

Question 15

Is there a quiz to learn the elements?

Accepted Answer

Yes. The Quiz tab has four modes — find an element on the table, name it from its symbol, name it from its atomic number, and give the symbol for a name — and you can limit questions to the first 20 or 36 elements. Your best streak is remembered in your browser.

Question 16

Where does the element data come from?

Accepted Answer

Values such as atomic mass, melting and boiling points, density, electronegativity, ionization energy and atomic radius follow standard reference data consistent with IUPAC and CRC Handbook values. Properties of the heaviest synthetic elements (from about element 100 onward) have never been measured and are predictions; the table marks them as predicted or unknown.

Question 17

Is this periodic table free and private?

Accepted Answer

Yes. It is completely free, with no account, no ads and no tracking of what you click. Everything runs in your browser; the site only counts anonymous page views with the cookie-free Simple Analytics.

#	Symbol	Element	Atomic mass	Group	Period	Electron configuration	Category
1	H	Hydrogen	1.008	1	1	1s¹	reactive nonmetal
2	He	Helium	4.003	18	1	1s²	noble gas
3	Li	Lithium	6.941	1	2	[He] 2s¹	alkali metal
4	Be	Beryllium	9.012	2	2	[He] 2s²	alkaline earth metal
5	B	Boron	10.81	13	2	[He] 2s² 2p¹	metalloid
6	C	Carbon	12.011	14	2	[He] 2s² 2p²	reactive nonmetal
7	N	Nitrogen	14.007	15	2	[He] 2s² 2p³	reactive nonmetal
8	O	Oxygen	15.999	16	2	[He] 2s² 2p⁴	reactive nonmetal
9	F	Fluorine	18.998	17	2	[He] 2s² 2p⁵	halogen
10	Ne	Neon	20.18	18	2	[He] 2s² 2p⁶	noble gas
11	Na	Sodium	22.99	1	3	[Ne] 3s¹	alkali metal
12	Mg	Magnesium	24.305	2	3	[Ne] 3s²	alkaline earth metal
13	Al	Aluminium	26.982	13	3	[Ne] 3s² 3p¹	post-transition metal
14	Si	Silicon	28.086	14	3	[Ne] 3s² 3p²	metalloid
15	P	Phosphorus	30.974	15	3	[Ne] 3s² 3p³	reactive nonmetal
16	S	Sulfur	32.06	16	3	[Ne] 3s² 3p⁴	reactive nonmetal
17	Cl	Chlorine	35.45	17	3	[Ne] 3s² 3p⁵	halogen
18	Ar	Argon	39.948	18	3	[Ne] 3s² 3p⁶	noble gas
19	K	Potassium	39.098	1	4	[Ar] 4s¹	alkali metal
20	Ca	Calcium	40.078	2	4	[Ar] 4s²	alkaline earth metal
21	Sc	Scandium	44.956	3	4	[Ar] 3d¹ 4s²	transition metal
22	Ti	Titanium	47.867	4	4	[Ar] 3d² 4s²	transition metal
23	V	Vanadium	50.942	5	4	[Ar] 3d³ 4s²	transition metal
24	Cr	Chromium	51.996	6	4	[Ar] 3d⁵ 4s¹	transition metal
25	Mn	Manganese	54.938	7	4	[Ar] 3d⁵ 4s²	transition metal
26	Fe	Iron	55.845	8	4	[Ar] 3d⁶ 4s²	transition metal
27	Co	Cobalt	58.933	9	4	[Ar] 3d⁷ 4s²	transition metal
28	Ni	Nickel	58.693	10	4	[Ar] 3d⁸ 4s²	transition metal
29	Cu	Copper	63.546	11	4	[Ar] 3d¹⁰ 4s¹	transition metal
30	Zn	Zinc	65.38	12	4	[Ar] 3d¹⁰ 4s²	transition metal
31	Ga	Gallium	69.723	13	4	[Ar] 3d¹⁰ 4s² 4p¹	post-transition metal
32	Ge	Germanium	72.63	14	4	[Ar] 3d¹⁰ 4s² 4p²	metalloid
33	As	Arsenic	74.922	15	4	[Ar] 3d¹⁰ 4s² 4p³	metalloid
34	Se	Selenium	78.971	16	4	[Ar] 3d¹⁰ 4s² 4p⁴	reactive nonmetal
35	Br	Bromine	79.904	17	4	[Ar] 3d¹⁰ 4s² 4p⁵	halogen
36	Kr	Krypton	83.798	18	4	[Ar] 3d¹⁰ 4s² 4p⁶	noble gas
37	Rb	Rubidium	85.468	1	5	[Kr] 5s¹	alkali metal
38	Sr	Strontium	87.62	2	5	[Kr] 5s²	alkaline earth metal
39	Y	Yttrium	88.906	3	5	[Kr] 4d¹ 5s²	transition metal
40	Zr	Zirconium	91.224	4	5	[Kr] 4d² 5s²	transition metal
41	Nb	Niobium	92.906	5	5	[Kr] 4d⁴ 5s¹	transition metal
42	Mo	Molybdenum	95.95	6	5	[Kr] 4d⁵ 5s¹	transition metal
43	Tc	Technetium	98	7	5	[Kr] 4d⁵ 5s²	transition metal
44	Ru	Ruthenium	101.07	8	5	[Kr] 4d⁷ 5s¹	transition metal
45	Rh	Rhodium	102.91	9	5	[Kr] 4d⁸ 5s¹	transition metal
46	Pd	Palladium	106.42	10	5	[Kr] 4d¹⁰	transition metal
47	Ag	Silver	107.87	11	5	[Kr] 4d¹⁰ 5s¹	transition metal
48	Cd	Cadmium	112.41	12	5	[Kr] 4d¹⁰ 5s²	transition metal
49	In	Indium	114.82	13	5	[Kr] 4d¹⁰ 5s² 5p¹	post-transition metal
50	Sn	Tin	118.71	14	5	[Kr] 4d¹⁰ 5s² 5p²	post-transition metal
51	Sb	Antimony	121.76	15	5	[Kr] 4d¹⁰ 5s² 5p³	metalloid
52	Te	Tellurium	127.6	16	5	[Kr] 4d¹⁰ 5s² 5p⁴	metalloid
53	I	Iodine	126.9	17	5	[Kr] 4d¹⁰ 5s² 5p⁵	halogen
54	Xe	Xenon	131.29	18	5	[Kr] 4d¹⁰ 5s² 5p⁶	noble gas
55	Cs	Caesium	132.91	1	6	[Xe] 6s¹	alkali metal
56	Ba	Barium	137.33	2	6	[Xe] 6s²	alkaline earth metal
57	La	Lanthanum	138.91	—	6	[Xe] 5d¹ 6s²	lanthanide
58	Ce	Cerium	140.12	—	6	[Xe] 4f¹ 5d¹ 6s²	lanthanide
59	Pr	Praseodymium	140.91	—	6	[Xe] 4f³ 6s²	lanthanide
60	Nd	Neodymium	144.24	—	6	[Xe] 4f⁴ 6s²	lanthanide
61	Pm	Promethium	145	—	6	[Xe] 4f⁵ 6s²	lanthanide
62	Sm	Samarium	150.36	—	6	[Xe] 4f⁶ 6s²	lanthanide
63	Eu	Europium	151.96	—	6	[Xe] 4f⁷ 6s²	lanthanide
64	Gd	Gadolinium	157.25	—	6	[Xe] 4f⁷ 5d¹ 6s²	lanthanide
65	Tb	Terbium	158.93	—	6	[Xe] 4f⁹ 6s²	lanthanide
66	Dy	Dysprosium	162.5	—	6	[Xe] 4f¹⁰ 6s²	lanthanide
67	Ho	Holmium	164.93	—	6	[Xe] 4f¹¹ 6s²	lanthanide
68	Er	Erbium	167.26	—	6	[Xe] 4f¹² 6s²	lanthanide
69	Tm	Thulium	168.93	—	6	[Xe] 4f¹³ 6s²	lanthanide
70	Yb	Ytterbium	173.05	—	6	[Xe] 4f¹⁴ 6s²	lanthanide
71	Lu	Lutetium	174.97	—	6	[Xe] 4f¹⁴ 5d¹ 6s²	lanthanide
72	Hf	Hafnium	178.49	4	6	[Xe] 4f¹⁴ 5d² 6s²	transition metal
73	Ta	Tantalum	180.95	5	6	[Xe] 4f¹⁴ 5d³ 6s²	transition metal
74	W	Tungsten	183.84	6	6	[Xe] 4f¹⁴ 5d⁴ 6s²	transition metal
75	Re	Rhenium	186.21	7	6	[Xe] 4f¹⁴ 5d⁵ 6s²	transition metal
76	Os	Osmium	190.23	8	6	[Xe] 4f¹⁴ 5d⁶ 6s²	transition metal
77	Ir	Iridium	192.22	9	6	[Xe] 4f¹⁴ 5d⁷ 6s²	transition metal
78	Pt	Platinum	195.08	10	6	[Xe] 4f¹⁴ 5d⁹ 6s¹	transition metal
79	Au	Gold	196.97	11	6	[Xe] 4f¹⁴ 5d¹⁰ 6s¹	transition metal
80	Hg	Mercury	200.59	12	6	[Xe] 4f¹⁴ 5d¹⁰ 6s²	transition metal
81	Tl	Thallium	204.38	13	6	[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p¹	post-transition metal
82	Pb	Lead	207.2	14	6	[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p²	post-transition metal
83	Bi	Bismuth	208.98	15	6	[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p³	post-transition metal
84	Po	Polonium	209	16	6	[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁴	post-transition metal
85	At	Astatine	210	17	6	[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁵	halogen
86	Rn	Radon	222	18	6	[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁶	noble gas
87	Fr	Francium	223	1	7	[Rn] 7s¹	alkali metal
88	Ra	Radium	226	2	7	[Rn] 7s²	alkaline earth metal
89	Ac	Actinium	227	—	7	[Rn] 6d¹ 7s²	actinide
90	Th	Thorium	232.04	—	7	[Rn] 6d² 7s²	actinide
91	Pa	Protactinium	231.04	—	7	[Rn] 5f² 6d¹ 7s²	actinide
92	U	Uranium	238.03	—	7	[Rn] 5f³ 6d¹ 7s²	actinide
93	Np	Neptunium	[237]	—	7	[Rn] 5f⁴ 6d¹ 7s²	actinide
94	Pu	Plutonium	[244]	—	7	[Rn] 5f⁶ 7s²	actinide
95	Am	Americium	[243]	—	7	[Rn] 5f⁷ 7s²	actinide
96	Cm	Curium	[247]	—	7	[Rn] 5f⁷ 6d¹ 7s²	actinide
97	Bk	Berkelium	[247]	—	7	[Rn] 5f⁹ 7s²	actinide
98	Cf	Californium	[251]	—	7	[Rn] 5f¹⁰ 7s²	actinide
99	Es	Einsteinium	[252]	—	7	[Rn] 5f¹¹ 7s²	actinide
100	Fm	Fermium	[257]	—	7	[Rn] 5f¹² 7s²	actinide
101	Md	Mendelevium	[258]	—	7	[Rn] 5f¹³ 7s²	actinide
102	No	Nobelium	[259]	—	7	[Rn] 5f¹⁴ 7s²	actinide
103	Lr	Lawrencium	[266]	—	7	[Rn] 5f¹⁴ 7s² 7p¹	actinide
104	Rf	Rutherfordium	[267]	4	7	[Rn] 5f¹⁴ 6d² 7s²	transition metal
105	Db	Dubnium	[268]	5	7	[Rn] 5f¹⁴ 6d³ 7s²	transition metal
106	Sg	Seaborgium	[269]	6	7	[Rn] 5f¹⁴ 6d⁴ 7s²	transition metal
107	Bh	Bohrium	[270]	7	7	[Rn] 5f¹⁴ 6d⁵ 7s²	transition metal
108	Hs	Hassium	[277]	8	7	[Rn] 5f¹⁴ 6d⁶ 7s²	transition metal
109	Mt	Meitnerium	[278]	9	7	[Rn] 5f¹⁴ 6d⁷ 7s²	transition metal
110	Ds	Darmstadtium	[281]	10	7	[Rn] 5f¹⁴ 6d⁸ 7s²	transition metal
111	Rg	Roentgenium	[282]	11	7	[Rn] 5f¹⁴ 6d⁹ 7s²	transition metal
112	Cn	Copernicium	[285]	12	7	[Rn] 5f¹⁴ 6d¹⁰ 7s²	transition metal
113	Nh	Nihonium	[286]	13	7	[Rn] 5f¹⁴ 6d¹⁰ 7s² 7p¹	post-transition metal
114	Fl	Flerovium	[289]	14	7	[Rn] 5f¹⁴ 6d¹⁰ 7s² 7p²	post-transition metal
115	Mc	Moscovium	[290]	15	7	[Rn] 5f¹⁴ 6d¹⁰ 7s² 7p³	post-transition metal
116	Lv	Livermorium	[293]	16	7	[Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁴	post-transition metal
117	Ts	Tennessine	[294]	17	7	[Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁵	halogen
118	Og	Oganesson	[294]	18	7	[Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁶	noble gas

# What is the periodic table?

# How to read an element tile

# Element categories

# Periodic trends

# List of all 118 elements

# Frequently asked questions

# Related tools

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Interactive Periodic Table of Elements — all 118 elements with names, symbols, atomic mass and electron configuration