Periodic Table
with Atomic Mass
Explore our interactive periodic table to easily find the atomic mass, atomic number, and symbol for all 118 elements.
Interactive Periodic Table Hub
Hover over any element to explore its atomic properties and access specialized deep-dive guides.
What is the Periodic Table of Elements?
The periodic table is the most iconic map in science. It is a tabular display of all known chemical elements, arranged by their atomic number, electron configuration, and recurring chemical properties. It is not just a chart; it is a fundamental framework that allows chemists and physicists to understand the building blocks of the universe.
In its modern form, the periodic table organizes 118 confirmed elements into 18 columns (groups) and 7 rows (periods). This arrangement is far from arbitrary; it reflects the underlying quantum mechanical structure of atoms, specifically the way electrons occupy different energy levels or "shells."
Core Search Intent: "How many elements are on the periodic table?"
As of today, there are 118 confirmed elements on the periodic table. The last four elements (Nihonium, Moscovium, Tennessine, and Oganesson) were officially added in 2016, completing the 7th period. While researchers are currently searching for element 119 and beyond, 118 remains the official count.
- 94Naturally occurring elements found on Earth.
- 24Synthetic elements created in laboratories.
- 118Total elements as recognized by IUPAC.
Who Invented the Periodic Table?
The story of the periodic table's creation is one of the most famous episodes in scientific history. While many scientists contributed (including Johann Döbereiner, John Newlands, and Lothar Meyer), the primary credit goes to the Russian chemist Dmitri Mendeleev.
1869Mendeleev's Dream
Legend says Mendeleev saw the structure of the table in a dream after years of trying to organize elements by their atomic weights. He famously wrote each element on a card and played "chemical solitaire" until they fell into place.
PREDPredictive Power
What made Mendeleev's table superior was his willingness to leave empty gaps. He predicted that elements not yet discovered would fill these spots and even calculated their properties (like Gallium and Germanium) with stunning accuracy.
MODThe Modern Shift
In 1913, Henry Moseley used X-ray spectroscopy to prove that the table should be ordered by atomic number (protons) rather than atomic weight, resolving the few anomalies in Mendeleev's original design.
How is the Periodic Table Organized?
The table's layout is its most powerful feature. It is divided into Periods (horizontal rows) and Groups (vertical columns), each revealing different secrets about an element's nature.
What is a Period?
A period is a horizontal row in the periodic table. There are 7 periods in total.
- ✓Elements in the same period have the same number of occupied electron shells.
- ✓Period 1 has 1 shell, Period 2 has 2 shells, and so on.
- ✓As you move from left to right across a period, the atomic number increases, and properties shift from metallic to non-metallic.
What is a Group?
A group (or family) is a vertical column. There are 18 numbered groups.
- ✓Elements in the same group usually have the same number of valence electrons.
- ✓Because they have similar valence counts, they exhibit similar chemical behavior.
- ✓Example: All Group 18 elements (Noble Gases) are stable and rarely react because their outer shells are full.
Periodic Trends & Search Intents
The periodic table allows us to predict the behavior of elements through "trends"—patterns that emerge as you move across rows or down columns.
Electronegativity Periodic Table
Electronegativity is a measure of how strongly an atom attracts electrons in a chemical bond.
- Trend:Increases as you move left to right across a period.
- Trend:Decreases as you move down a group.
- Champion:Fluorine is the most electronegative element (4.0 on the Pauling scale).
Visualizing Electron Attraction
Atomic Volume Measurement
Atomic Radius Periodic Table
Atomic radius represents the size of the atom, measured as the distance from the nucleus to the boundary of the electron cloud.
- Trend:Decreases left to right across a period (due to higher nuclear charge pulling shells tighter).
- Trend:Increases down a group (due to adding new electron shells).
- Champion:Cesium has one of the largest atomic radii among stable elements.
Valence Electrons Periodic Table
Valence electrons are the electrons in the outermost shell. These are the "active" electrons that participate in bonding.
Group 1
1
Group 2
2
Group 13
3
Group 18
8*
*Helium is in Group 18 but has only 2 valence electrons because its first shell is full with 2.
Metals, Nonmetals & Metalloids
Metals
Occupying roughly 80% of the table, metals are located on the left and middle. They are typically shiny, conductive, and malleable.
- • Alkali Metals (Group 1)
- • Alkaline Earth Metals (Group 2)
- • Transition Metals (Groups 3-12)
- • Lanthanides & Actinides
Metalloids
These elements sit along the "staircase" line. They share properties of both metals and nonmetals.
- • Boron (B)
- • Silicon (Si)
- • Germanium (Ge)
- • Arsenic (As), Antimony (Sb), Tellurium (Te)
Nonmetals
Found on the right side of the table. They vary in appearance and are generally poor conductors of heat and electricity.
- • Reactive Nonmetals (C, N, O, P, S, Se)
- • Halogens (Group 17)
- • Noble Gases (Group 18)
Deep Dive: Periodic Table Groups
Group 1: Alkali Metals
Except for Hydrogen, Group 1 consists of the Alkali Metals. These are soft, silvery metals that are extremely reactive. They have only one valence electron, which they "want" to lose desperately to achieve stability.
Did you know?
Sodium and Potassium are so reactive that they must be stored in oil to prevent them from reacting with moisture in the air. When dropped in water, they explode!
Group 17: The Halogens
The Halogens are a group of highly reactive nonmetals. They have 7 valence electrons and are just one electron short of a full shell. This makes them "hungry" for electrons.
Includes: Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), and Astatine (At).
Group 18: The Noble Gases
Formerly known as the inert gases, the Noble Gases are the royalty of the periodic table. They have full outer shells, making them extremely stable and non-reactive under standard conditions.
Includes: Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), and Radon (Rn).
Periodic Table with Charges
Atoms "want" to have a full outer shell (usually 8 electrons). To do this, they will either lose or gain electrons, which gives them an electric charge.
| Group Number | Typical Ionic Charge | Common Examples |
|---|---|---|
| Group 1 | +1 | Li⁺, Na⁺, K⁺ |
| Group 2 | +2 | Mg²⁺, Ca²⁺ |
| Group 13 | +3 | Al³⁺ |
| Group 15 | -3 | N³⁻, P³⁻ |
| Group 16 | -2 | O²⁻, S²⁻ |
| Group 17 | -1 | F⁻, Cl⁻, Br⁻ |
What is 67 on the Periodic Table?
Element number 67 is Holmium (Ho). It is a rare earth metal belonging to the Lanthanide series.
- ✓Found in Period 6.
- ✓Atomic mass: 164.93 u.
- ✓Known for having the highest magnetic strength of any element.
- ✓Used in high-power magnets and medical lasers.
How to Read the Periodic Table
Reading an element's box is like reading its resume. Every symbol and number tells you something important about its "personality."
6
C
Carbon
12.011
Atomic Number
The whole number at the top. It tells you exactly how many protons are in the nucleus.
Element Symbol
One or two letters that represent the element's name (e.g., C for Carbon, Au for Gold).
Atomic Mass
The decimal number at the bottom. It's the weighted average mass of all naturally occurring versions (isotopes) of the element.
Periodic Table — Common Questions
What is the periodic table?
The periodic table is a tabular map of chemical elements, organized by their atomic number and electron configuration to show recurring chemical trends.
How many periods are in the periodic table?
There are 7 horizontal periods in the modern periodic table. Each period corresponds to the number of electron shells an atom has.
How many groups are in the periodic table?
There are 18 vertical groups. Elements in the same group share similar valence electron counts and chemical properties.
Where are metals located on the periodic table?
Metals occupy the left side and the middle sections of the periodic table, separated from nonmetals by a staircase-like diagonal of metalloids.
Can I lick it periodic table?
Definitely not! While some elements like Iron or Calcium are nutrients, many elements on the table are highly toxic (like Lead), radioactive (like Uranium), or corrosive (like Fluorine).
What is a group on the periodic table?
A group is a vertical column. It represents a family of elements that have the same number of electrons in their outer shell, making them react in similar ways.
What is a period on the periodic table?
A period is a horizontal row. Moving across a period, the atomic number increases as protons and electrons are added to the same principal shell.
Who invented the periodic table?
Dmitri Mendeleev is widely credited with the invention of the periodic table in 1869, primarily because he used his chart to predict the existence of undiscovered elements.
Quantum Mechanics: The "Why" Behind the Table
The periodic table isn't just a convenient way to list elements; it's a direct visualization of Quantum Mechanics. Every row and column is dictated by the Pauli Exclusion Principle and the way electrons fill orbitals (s, p, d, and f).
As we move to more complex atoms, we encounter the SPDF model. Group 1 & 2 elements are the "s-block," Groups 13-18 are the "p-block," transition metals are the "d-block," and those two rows at the bottom? Those are the "f-block" lanthanides and actinides.
Your Reliable Chemistry Resource
This interactive periodic table and guide were built to provide the most accurate, up-to-date data for students, educators, and science enthusiasts. We cross-reference all values with IUPAC and NIST databases to ensure scientific integrity.
By Emmanuel TUYISHIMIRE · May 2026 · Last Reviewed May 2026
Emmanuel TUYISHIMIRE (Toni)
Principal Software Engineer & STEM Educator · Toni Tech Solution · Kigali, Rwanda
Toni cross-references every data value on this site against at least three authoritative sources: PubChem, NIST Chemistry WebBook, and the Royal Society of Chemistry. When sources conflict, all three are cited and the discrepancy is explained. Read the full methodology →
Data Sources & References
All numerical values on this page are sourced from and cross-referenced against the following authoritative databases:
- PubChem (National Library of Medicine)— Element property database, NCBI/NIH
- NIST Chemistry WebBook— National Institute of Standards and Technology
- Royal Society of Chemistry — Periodic Table— RSC authoritative element data
- Pauling, L. (1932)— The Nature of the Chemical Bond, original electronegativity scale