The Periodic Table Calculator helps you quickly find important information about any chemical element. Enter an element name, symbol, or atomic number to check properties such as atomic number, atomic mass, protons, neutrons, and electrons.
This calculator is useful for chemistry homework, classroom exercises, lab preparation, and exam study. Instead of searching through a large periodic table, you can use the calculator to find key element information in seconds.
What Can the Periodic Table Calculator Find?
Depending on the element and information provided, the calculator can help you identify:
- Atomic number — the number of protons in an atom.
- Atomic mass — the average mass of an element’s naturally occurring isotopes, usually shown in atomic mass units (amu).
- Protons — positively charged particles found in the nucleus.
- Neutrons — neutral particles found in the nucleus.
- Electrons — negatively charged particles surrounding the nucleus.
- Element symbol — the one- or two-letter abbreviation used for the element.
- Element name — the full name of the chemical element.
How Does a Periodic Table Calculator Work?
The calculator uses the relationships between the basic properties of an element. The atomic number identifies the element because it equals the number of protons in a neutral atom.
For a neutral atom, the number of electrons is also equal to the atomic number. The number of neutrons can be estimated from the mass number using:
Neutrons = Mass Number − Atomic Number
For example, carbon has an atomic number of 6. A carbon-12 atom has a mass number of 12, so it contains:
12 − 6 = 6 neutrons
It also has 6 protons and, when neutral, 6 electrons.
Use the calculator below to find these values quickly and make periodic table problems easier to understand and solve.
Periodic Table Calculator: Atomic Number, Mass & Particles
Find atomic number, atomic mass, protons, neutrons, electrons, group, period, and element category for any chemical element.
Find an Element
Carbon
* Neutron count uses Carbon-12, the selected/default isotope. Atomic mass and mass number are different concepts.
Isotope & Particle Calculator
Electrons = Atomic Number − Charge = 6 − 0 = 6
Selection controls
Atomic Structure
Electron Shells
Core formulas
Z = Number of ProtonsA = Protons + NeutronsN = A − ZElectrons = Atomic NumberElectrons = Atomic Number − ChargeInteractive Periodic Table
Element Details
What does the Periodic Table Calculator calculate?
Atomic number identifies an element and equals its number of protons. Atomic mass is usually a weighted average of an element’s naturally occurring isotopes.
For a chosen isotope, the mass number is the total of protons and neutrons, so neutrons equal mass number minus atomic number. A neutral atom has the same number of electrons as protons; an ion gains or loses electrons according to its charge.
- Group is the element’s column, and period is its row.
- Category describes broad chemical behavior such as nonmetal, halogen, or noble gas.
- If a reference property is not included or appropriate, the calculator shows “Not available” rather than guessing.
Carbon-12
Symbol: C
Atomic number: 6
Mass number: 12
Protons = 6
Neutrons = 12 − 6 = 6
Electrons = 6
What Is a Periodic Table Calculator?
A Periodic Table Calculator is an online chemistry tool that helps you find important information about chemical elements. It uses data from the periodic table to show properties such as an element’s atomic number, atomic mass, protons, neutrons, and electrons.
The periodic table organizes elements by their atomic number and groups elements with similar chemical properties. Each element has a unique atomic number, which tells you how many protons are in its nucleus.
What Information Can Be Found from the Periodic Table?
A periodic table provides many useful details about each element. Common information includes:
Element name: The full name of the element, such as Carbon or Oxygen.
Chemical symbol: The one- or two-letter abbreviation, such as C or O.
Atomic number: The number of protons in the nucleus.
Atomic mass: The average mass of the element’s naturally occurring isotopes.
Electron information: The number of electrons in a neutral atom and, in many tables, its electron configuration.
Group and period: The element’s position in the periodic table.
Element category: Such as metal, nonmetal, metalloid, noble gas, or halogen.
The exact information available depends on the periodic table or calculator you use.
How Does a Calculator Make Element Calculations Easier?
Some chemistry questions require you to use periodic table values in calculations. A calculator can organize these values in one place, reducing the need to search through a full periodic table manually.
For example, once you know an element’s atomic number, you can determine the number of protons. For a neutral atom, the number of electrons is equal to the number of protons.
If a mass number is provided, you can also calculate the number of neutrons:
Neutrons = Mass Number − Atomic Number
This makes common atomic-structure questions faster and easier to check.
Who Can Use a Periodic Table Calculator?
A Periodic Table Calculator can be useful for:
High school students learning atomic structure and periodic table basics.
AP Chemistry and other chemistry students working on atomic calculations.
College and university students reviewing general chemistry concepts.
Beginner chemistry learners who need quick access to element information.
Students checking homework or verifying calculations before submitting their work.
It is especially helpful when you need a quick reference while studying or solving chemistry problems.
How to Use a Periodic Table Calculator
Using a Periodic Table Calculator is simple. Follow these steps to find the information you need.
1. Select or Search for an Element
Start by selecting an element from the periodic table or searching for it by name, symbol, or atomic number, depending on the calculator.
For example, you could search for Oxygen, O, or atomic number 8. The calculator can then display the available information for that element.
2. Find the Atomic Number and Atomic Mass
After selecting an element, look for its atomic number and atomic mass.
The atomic number identifies the element and equals the number of protons in its nucleus. Atomic mass is commonly displayed as a decimal because it represents the weighted average of the masses of the element’s naturally occurring isotopes.
For example, oxygen has an atomic number of 8 and a standard atomic weight of about 16.00 atomic mass units.
3. Determine Protons, Neutrons, and Electrons
The atomic number helps you determine the number of protons and electrons in a neutral atom.
Protons = Atomic Number
Electrons = Atomic Number for a neutral atom.
To determine neutrons, you need the mass number of a specific isotope:
Neutrons = Mass Number − Atomic Number
For example, oxygen-16 has an atomic number of 8 and a mass number of 16.
Neutrons = 16 − 8 = 8
Therefore, a neutral oxygen-16 atom contains 8 protons, 8 neutrons, and 8 electrons.
Remember that atomic mass and mass number are not the same thing. Atomic mass is usually an average value, while mass number is the total number of protons and neutrons in one specific isotope.
4. Understand the Additional Element Information
A calculator may provide more than basic atomic information. Depending on the tool, you may also see the element’s symbol, group, period, category, electron configuration, atomic mass, and other properties.
Use these details to understand where the element appears on the periodic table and how its atomic structure relates to its properties.
For the most accurate chemistry work, always distinguish between atomic number, atomic mass, and mass number. These values are related, but they serve different purposes in atomic calculations.
How to Calculate Protons, Neutrons, and Electrons
Protons, neutrons, and electrons are the three main subatomic particles used to describe an atom. Their numbers help you identify an element, determine its isotope, and understand whether an atom is neutral or charged.
The atomic number gives you the number of protons. The number of electrons depends on whether the atom is neutral or an ion. To find neutrons, you use the mass number of a specific isotope.
How to Calculate Protons
The number of protons in an atom is equal to its atomic number.
Number of Protons = Atomic Number
Every element has a unique atomic number. Changing the number of protons changes the element itself.
Example: Oxygen
Oxygen has an atomic number of 8.
Therefore:
Protons = 8
Every oxygen atom has 8 protons, regardless of which oxygen isotope it is.
How to Calculate Neutrons From the Periodic Table
To calculate neutrons, you need the mass number and atomic number.
Number of Neutrons = Mass Number − Atomic Number
Follow these steps:
Identify the element’s atomic number.
Find the mass number of the isotope you are studying.
Subtract the atomic number from the mass number.
The result is the number of neutrons.
Example: Carbon-12
Carbon has an atomic number of 6. Carbon-12 has a mass number of 12.
Neutrons = 12 − 6
Neutrons = 6
Therefore, a carbon-12 atom contains 6 neutrons.
Mass Number vs. Average Atomic Mass
It is important not to confuse mass number with average atomic mass.
The mass number is the total number of protons and neutrons in one specific atom or isotope. It is always a whole number.
The average atomic mass shown on most periodic tables is a weighted average based on the naturally occurring isotopes of an element. It often contains decimals.
For example, chlorine has an average atomic mass of about 35.45 amu because naturally occurring chlorine consists mainly of different isotopes.
When calculating neutrons for a specific isotope, use its mass number, not the decimal average atomic mass.
How to Calculate Electrons
The number of electrons depends on whether the atom is neutral or an ion.
Neutral Atoms
A neutral atom has no overall electrical charge. Therefore, it has equal numbers of protons and electrons.
Electrons = Protons = Atomic Number
Example: Sodium
Sodium has an atomic number of 11.
A neutral sodium atom has:
11 protons
11 electrons
Positive Ions
A positive ion, called a cation, has lost one or more electrons. Therefore, it has fewer electrons than protons.
Example: Na⁺
A sodium atom has 11 protons. A Na⁺ ion has lost one electron.
Electrons = 11 − 1 = 10
So, Na⁺ has 10 electrons.
Negative Ions
A negative ion, called an anion, has gained one or more electrons. Therefore, it has more electrons than protons.
Example: Cl⁻
Chlorine has 17 protons. A Cl⁻ ion has gained one electron.
Electrons = 17 + 1 = 18
So, Cl⁻ has 18 electrons.
Understanding Atomic Number and Atomic Mass
Atomic number and atomic mass are two of the most important values shown on the periodic table. Understanding the difference between them helps you correctly identify elements and solve problems involving protons, neutrons, and electrons.
What Is Atomic Number?
The atomic number is the number of protons in the nucleus of an atom.
Atomic Number = Number of Protons
This number uniquely identifies an element. For example, hydrogen has atomic number 1, carbon has atomic number 6, and oxygen has atomic number 8.
The atomic number does not change between isotopes of the same element. For example, every carbon isotope has 6 protons.
For a neutral atom, the atomic number also equals the number of electrons.
What Is Atomic Mass?
Atomic mass is the weighted average mass of an element’s naturally occurring isotopes. It is commonly expressed in atomic mass units (amu).
Atomic mass often contains a decimal because most elements exist naturally as a mixture of isotopes with different masses.
For example, chlorine has an average atomic mass of approximately 35.45 amu. This does not mean that every chlorine atom has exactly 35.45 protons and neutrons. Instead, it reflects the average of the naturally occurring chlorine isotopes.
Atomic Mass vs. Mass Number
Although the terms sound similar, atomic mass and mass number have different meanings.
| Feature | Atomic Mass | Mass Number |
|---|---|---|
| Meaning | Weighted average of naturally occurring isotopes | Protons + neutrons in one isotope |
| Usually shown as | Decimal | Whole number |
| Applies to | The element’s natural isotopic mixture | A specific isotope |
| Used to calculate neutrons? | Not directly | Yes |
The mass number is calculated as:
Mass Number = Protons + Neutrons
Therefore:
Neutrons = Mass Number − Atomic Number
For example, carbon-14 has 6 protons and a mass number of 14.
Neutrons = 14 − 6 = 8
The distinction matters because the periodic table usually gives you average atomic mass, while neutron calculations require the mass number of a specific isotope.
How to Read the Periodic Table
The periodic table is organized so you can quickly find important information about each chemical element. Once you understand what the numbers, symbols, rows, and columns mean, you can use it to solve many basic chemistry problems.
Element Name
The element name identifies the chemical element. Examples include Hydrogen, Carbon, Oxygen, Iron, and Gold.
Each element has its own position on the periodic table.
Chemical Symbol
The chemical symbol is a short abbreviation for an element. It usually contains one or two letters.
The first letter is always capitalized. If there is a second letter, it is lowercase.
Examples include:
Hydrogen — H
Carbon — C
Oxygen — O
Sodium — Na
Chlorine — Cl
Chemical symbols are commonly used in chemical formulas and equations.
Atomic Number
The atomic number identifies an element and tells you the number of protons in its nucleus.
For example, oxygen has atomic number 8, so every oxygen atom has 8 protons.
For a neutral atom, the atomic number also tells you the number of electrons.
Atomic Mass
The atomic mass is usually displayed as a decimal number on a periodic table. It represents the weighted average of the naturally occurring isotopes of that element.
For example, an element may have an atomic mass of 10.81 amu. This decimal value is an average, not the number of particles inside one individual atom.
Groups
Groups are the vertical columns of the periodic table. There are 18 groups.
Elements in the same group often have related chemical properties because they have similar patterns in their outer electron arrangements.
Some important groups include:
Group 1: Alkali metals
Group 2: Alkaline earth metals
Groups 3–12: Transition metals
Group 17: Halogens
Group 18: Noble gases
Periods
Periods are the horizontal rows of the periodic table. There are 7 periods.
As you move from left to right across a period, the atomic number generally increases by one from one element to the next.
The period number is also related to the occupied principal energy levels in an atom.
Element Categories
The periodic table also classifies elements into broad categories based on their properties.
Common categories include:
Metals — generally good conductors of heat and electricity.
Nonmetals — generally have different physical and chemical properties from metals.
Metalloids — have properties between those of metals and nonmetals.
Noble gases — elements in Group 18 with very low chemical reactivity under ordinary conditions.
Halogens — highly reactive nonmetals in Group 17.
Alkali metals — highly reactive metals in Group 1.
Knowing how to read these basic features makes it easier to find an element’s information and use the Periodic Table Calculator for chemistry calculations.
Periodic Table Groups and Periods
The periodic table is organized into groups and periods. Learning these two terms makes it easier to locate elements and understand their relationships.
What Are Groups?
Groups are the vertical columns of the periodic table. There are 18 groups.
Elements in the same group often have similar chemical properties because they have related outer-electron arrangements. For example, the elements in Group 1 are known as alkali metals.
What Are Periods?
Periods are the horizontal rows of the periodic table. There are 7 periods.
As you move from left to right across a period, the atomic number generally increases. The period also corresponds to the highest principal energy level occupied by electrons in the ground-state atom.
Why Are Groups and Periods Important?
Groups and periods help students quickly understand where an element belongs and how it relates to other elements. They are useful when studying electron arrangements, chemical properties, reactivity, and periodic trends.
Periodic Table Element Categories
Elements can also be grouped into broad categories based on their physical and chemical properties.
Alkali metals: Group 1 elements, excluding hydrogen. They are highly reactive metals and commonly form +1 ions.
Alkaline earth metals: Group 2 elements. They are reactive metals that commonly form +2 ions.
Transition metals: Elements in Groups 3–12. They are metals with characteristic metallic properties and often form multiple types of ions.
Metalloids: Elements with properties that fall between metals and nonmetals. Silicon and boron are common examples.
Nonmetals: Elements that generally do not show typical metallic properties. They include elements such as carbon, oxygen, nitrogen, and sulfur.
Halogens: Group 17 elements. They are reactive nonmetals that commonly form −1 ions.
Noble gases: Group 18 elements. They are generally very unreactive under ordinary conditions.
Lanthanides: A series of 15 elements, from lanthanum through lutetium, commonly shown in the upper of the two detached rows below the main table.
Actinides: A series of 15 elements, from actinium through lawrencium, commonly shown in the lower detached row. Many are radioactive.
These categories help you recognize broad patterns in element behavior and periodic trends.
Periodic Table Calculator Examples
The following examples show how periodic table information can be used to determine the number of protons, neutrons, and electrons.
Example: Carbon
Consider carbon-12 (C-12).
| Property | Value |
|---|---|
| Atomic number | 6 |
| Atomic mass | About 12.011 amu |
| Mass number | 12 |
| Protons | 6 |
| Neutrons | 6 |
| Electrons | 6 |
Step 1: Find protons
Carbon’s atomic number is 6, so it has 6 protons.
Step 2: Find neutrons
For carbon-12:
Neutrons = Mass Number − Atomic Number
Neutrons = 12 − 6 = 6
Step 3: Find electrons
A neutral carbon atom has the same number of electrons as protons.
Electrons = 6
Therefore, carbon-12 has 6 protons, 6 neutrons, and 6 electrons.
Note that the periodic table’s atomic mass, about 12.011 amu, is an average value. The 12 used for the neutron calculation is the mass number of carbon-12.
Example: Oxygen
Consider oxygen-16 (O-16).
| Property | Value |
|---|---|
| Atomic number | 8 |
| Atomic mass | About 15.999 amu |
| Mass number | 16 |
| Protons | 8 |
| Neutrons | 8 |
| Electrons | 8 |
Step 1: Find protons
Oxygen has an atomic number of 8.
Protons = 8
Step 2: Find neutrons
For oxygen-16:
Neutrons = 16 − 8 = 8
Step 3: Find electrons
Because the oxygen atom is neutral:
Electrons = 8
Therefore, oxygen-16 has 8 protons, 8 neutrons, and 8 electrons.
Again, the atomic mass shown on the periodic table is an average value. The mass number 16 refers specifically to oxygen-16.
Example: Sodium
Consider a neutral sodium-23 (Na-23) atom.
| Property | Value |
|---|---|
| Atomic number | 11 |
| Mass number | 23 |
| Protons | 11 |
| Neutrons | 12 |
| Electrons | 11 |
Step 1: Find protons
Sodium has an atomic number of 11.
Protons = 11
Step 2: Find neutrons
Sodium-23 has a mass number of 23.
Neutrons = 23 − 11 = 12
Step 3: Find electrons
The atom is neutral, so its number of electrons equals its number of protons.
Electrons = 11
Therefore, sodium-23 has 11 protons, 12 neutrons, and 11 electrons.
These examples show why it is important to identify whether a question gives an atomic mass or a specific mass number. Atomic mass is an average for the element, while mass number identifies a particular isotope and is used directly when calculating neutrons.
Common Mistakes When Using the Periodic Table
The periodic table is easy to use once you understand what each value means. However, students often make a few common mistakes when solving problems involving atomic structure. Knowing these errors can help you check your work and avoid incorrect calculations.
Confusing Atomic Mass With Mass Number
Atomic mass and mass number are related but not identical.
Atomic mass is the weighted average of an element’s naturally occurring isotopes. It is often a decimal.
Mass number is the total number of protons and neutrons in one specific isotope. It is a whole number.
For example, chlorine has an average atomic mass of about 35.45 amu, while chlorine-35 has a mass number of 35.
Using Atomic Mass Directly as an Exact Isotope Mass Number
A common mistake is to take the decimal atomic mass from the periodic table and use it directly to calculate neutrons.
For example, you should not automatically calculate chlorine’s neutrons as:
35.45 − 17 = 18.45
That does not represent the neutron count of a specific chlorine atom.
To calculate neutrons, you need the mass number of a specific isotope:
Neutrons = Mass Number − Atomic Number
For chlorine-35:
35 − 17 = 18 neutrons
For chlorine-37:
37 − 17 = 20 neutrons
Forgetting That Ions Can Have Different Numbers of Electrons
Neutral atoms have equal numbers of protons and electrons. Ions do not.
A positive ion has lost electrons, while a negative ion has gained electrons.
For example:
Na⁺: 11 protons and 10 electrons
Cl⁻: 17 protons and 18 electrons
The number of protons does not change when an atom becomes an ordinary ion. The change in electron count creates the electrical charge.
Confusing Atomic Number With Number of Neutrons
The atomic number tells you the number of protons, not the number of neutrons.
For example, oxygen has an atomic number of 8, so every oxygen atom has 8 protons. However, oxygen isotopes can have different numbers of neutrons.
For oxygen-16:
Neutrons = 16 − 8 = 8
For oxygen-18:
Neutrons = 18 − 8 = 10
So, always remember:
Atomic Number = Protons
Mass Number = Protons + Neutrons
Neutrons = Mass Number − Atomic Number
Keeping these relationships clear makes periodic table calculations much easier and helps you use a Periodic Table Calculator correctly.
Use the Periodic Table Calculator
Finding atomic information does not have to be complicated. The Periodic Table Calculator gives you quick access to important element properties and helps you work through common chemistry calculations.
Use it to check an element’s atomic number, atomic mass, protons, neutrons, and electrons. It can also help you review the difference between mass number and average atomic mass when solving isotope problems.
Whether you are completing chemistry homework, preparing for an exam, or reviewing atomic structure, the calculator can save time and help you check your calculations.
Ready to find an element’s atomic information? Use the calculator now.
Frequently Asked Questions
To calculate neutrons, subtract the atomic number from the mass number of a specific isotope.
Neutrons = Mass Number − Atomic Number
For example, carbon-12 has a mass number of 12 and an atomic number of 6, so it has 6 neutrons.
The number of protons is equal to the element's atomic number.
For example, oxygen has an atomic number of 8, so every oxygen atom has 8 protons.
For a neutral atom, the number of electrons equals the atomic number.
For example, sodium has atomic number 11, so a neutral sodium atom has 11 electrons. Ions have different numbers of electrons because they gain or lose electrons.
For a positive ion, subtract the charge from the atomic number. For a negative ion, add the charge magnitude to the atomic number.
For example, Na⁺ has 11 protons but 10 electrons, while Cl⁻ has 17 protons and 18 electrons.
The atomic number tells you the number of protons in an atom's nucleus. It identifies the element.
For a neutral atom, the atomic number also equals the number of electrons.
Atomic mass is the weighted average of the masses of an element's naturally occurring isotopes, so it is often a decimal.
Mass number is the total number of protons and neutrons in one specific isotope and is always a whole number.
A periodic table commonly provides an element's name, chemical symbol, atomic number, and average atomic mass.
It may also show its group, period, category, electron configuration, and other chemical properties.
Find the element on the periodic table and look for the number assigned to it, usually displayed near its chemical symbol.
For example, carbon has an atomic number of 6, meaning every carbon atom contains 6 protons.
Not always. The periodic table usually shows an element's average atomic mass, not the mass number of a specific isotope.
To calculate the exact number of neutrons, you need the isotope's mass number.
Neutrons = Mass Number − Atomic Number