Periodic Table of Elements
Explore all 118 chemical elements and their properties.
Showing 118 of 118 elements
Scroll horizontally to view the complete periodic table. Select any element to explore its properties.
Element information is provided as an educational reference. Atomic masses in square brackets represent the mass number of a representative isotope for elements without a standard atomic weight.
The periodic table is one of the most important tools in chemistry. It organizes all known chemical elements in a systematic way according to their atomic numbers and electronic structures. From the oxygen we breathe to the iron used in buildings and the silicon found in electronic devices, every chemical element has a place in the periodic table.
The periodic table makes it easier to study the properties of elements, understand how atoms behave, and predict how different elements react with one another. Instead of memorizing the properties of every element separately, we can use the arrangement of the periodic table to identify patterns and relationships between them.
The modern periodic table contains 118 confirmed chemical elements. These elements are arranged in rows called periods and columns called groups. Elements in the same group often have similar chemical properties because they have similar outer electron configurations.
Understanding the periodic table provides a strong foundation for learning chemistry, chemical bonding, atomic structure, chemical reactions, and many other scientific concepts.
What Is the Periodic Table?
The periodic table is a tabular arrangement of chemical elements based primarily on their increasing atomic numbers. Each element is represented by a chemical symbol and placed in a specific position according to its atomic number and electron configuration.
An element is a pure substance made up of atoms that contain the same number of protons in their nuclei. For example, every hydrogen atom contains one proton, while every carbon atom contains six protons.
The periodic table provides important information about each element, including:
Atomic number
Chemical symbol
Element name
Relative atomic mass
Group number
Period number
General chemical properties
The arrangement of elements also reveals periodic trends. These are repeating patterns in the physical and chemical properties of elements as we move across periods or down groups.
For example, elements in Group 1 are generally highly reactive metals, while elements in Group 18 are known as noble gases and are generally very unreactive.
History of the Periodic Table
The development of the periodic table took many years. Scientists gradually discovered new elements and studied their physical and chemical properties. Their work helped establish the modern arrangement of chemical elements.
Early Attempts to Classify Elements
Before the modern periodic table was developed, scientists tried different methods to organize known elements.
In 1829, German chemist Johann Wolfgang Döbereiner introduced the concept of triads. He observed that certain elements could be grouped into sets of three because they had similar chemical properties.
For example, lithium, sodium, and potassium formed one such group. Their properties showed a relationship, and the atomic mass of the middle element was approximately the average of the other two.
However, this method could not classify all known elements.
Newlands’ Law of Octaves
In 1864, English chemist John Newlands proposed the Law of Octaves.
He arranged elements in increasing order of atomic mass and observed that every eighth element showed similar properties to the first element in the sequence.
This pattern was compared to musical octaves. Although the idea was important, it worked mainly for lighter elements and could not explain the properties of all known elements.
Mendeleev’s Periodic Table
In 1869, Russian chemist Dmitri Mendeleev developed one of the earliest widely accepted periodic tables.
He arranged elements mainly according to increasing atomic mass and placed elements with similar chemical properties in the same groups.
One of his most important contributions was leaving gaps for elements that had not yet been discovered. He predicted the properties of these missing elements based on the properties of surrounding elements.
Later discoveries confirmed several of his predictions, demonstrating the importance of his arrangement.
Development of the Modern Periodic Table
Mendeleev’s arrangement was an important achievement, but some elements did not fit perfectly when arranged according to atomic mass.
In 1913, English physicist Henry Moseley studied the atomic numbers of elements using X-ray spectra. His work established that elements should be arranged according to increasing atomic number rather than atomic mass.
This became the foundation of the modern periodic table.
Today, the periodic table contains 118 confirmed elements, from hydrogen (H), atomic number 1, to oganesson (Og), atomic number 118.
Structure of the Modern Periodic Table
The modern periodic table is divided into horizontal rows, vertical columns, and four major blocks. Each part provides useful information about the electronic structure and chemical behavior of elements.
Periods
Horizontal rows in the periodic table are called periods.
There are seven periods in the modern periodic table. The period number generally corresponds to the highest occupied principal electron shell of an element in its ground-state electronic configuration.
For example:
Hydrogen and helium belong to Period 1.
Lithium to neon belong to Period 2.
Sodium to argon belong to Period 3.
Potassium to krypton belong to Period 4.
As we move from left to right across a period, the atomic number increases by one for each successive element.
The properties of elements also change gradually across a period. For example, metallic character generally decreases from left to right, while nonmetallic character generally increases.
Groups
Vertical columns in the periodic table are called groups.
There are 18 groups in the modern periodic table. Elements in the same group often show similar chemical properties because they have similar valence electron configurations.
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
For example, lithium, sodium, and potassium belong to Group 1. They are reactive metals and generally form ions with a positive charge of +1.
Blocks of the Periodic Table
The periodic table is also divided into four blocks based on the type of atomic orbital that receives the last electron in the ground-state electronic configuration.
These blocks are:
1. s-block
The s-block mainly includes Groups 1 and 2, along with hydrogen and helium based on their electron configurations.
These elements generally have their outermost electrons in an s orbital.
2. p-block
The p-block contains elements from Groups 13 to 18, except that helium is placed in Group 18 because of its chemical properties.
It includes metals, metalloids, nonmetals, halogens, and noble gases.
3. d-block
The d-block contains elements from Groups 3 to 12. These are commonly known as transition elements.
Many transition metals have high melting points, good electrical conductivity, and the ability to form compounds with different oxidation states.
4. f-block
The f-block consists of two rows usually displayed separately at the bottom of the periodic table.
These rows contain the lanthanoids and actinoids.
They are associated with the filling of f orbitals and include many important elements used in modern technologies.
Classification of Elements in the Periodic Table
Elements can be classified into different categories according to their physical and chemical properties.
Metals
Metals are elements that generally have properties such as metallic shine, good electrical conductivity, and good thermal conductivity.
Most metals are solid at room temperature, although mercury is an important exception because it is liquid under ordinary room conditions.
Common examples include:
Iron (Fe)
Copper (Cu)
Aluminium (Al)
Gold (Au)
Silver (Ag)
Sodium (Na)
Metals are widely used in construction, electrical equipment, transportation, machinery, and manufacturing.
Nonmetals
Nonmetals generally have properties different from those of metals. Many are poor conductors of heat and electricity.
They may exist as solids, liquids, or gases at room temperature.
Examples include:
Oxygen (O)
Nitrogen (N)
Carbon (C)
Sulfur (S)
Chlorine (Cl)
Phosphorus (P)
Nonmetals play important roles in living organisms, chemical reactions, industrial processes, and environmental systems.
Metalloids
Metalloids are elements that show a mixture of metallic and nonmetallic characteristics.
Their properties often fall between those of metals and nonmetals.
Common examples include:
Boron (B)
Silicon (Si)
Germanium (Ge)
Arsenic (As)
Antimony (Sb)
Tellurium (Te)
Silicon is particularly important because of its semiconductor properties. It is widely used in computer chips, solar cells, and electronic devices.
Noble Gases
Noble gases belong to Group 18 of the periodic table.
They generally have very low chemical reactivity because their outer electron shells are filled.
Examples include:
Helium (He)
Neon (Ne)
Argon (Ar)
Krypton (Kr)
Xenon (Xe)
Radon (Rn)
Oganesson (Og)
Helium is used in balloons and certain cooling applications, while neon is used in lighting.
Halogens
Halogens are the elements in Group 17.
They are reactive nonmetals and generally have seven valence electrons.
Examples include fluorine, chlorine, bromine, iodine, and astatine. Tennessine is also included in this group.
Halogens can react with metals to form salts. For example, sodium reacts with chlorine to produce sodium chloride, commonly known as table salt.
Important Families of Elements
Some groups of the periodic table are known as element families because their members share important chemical characteristics.
Alkali Metals
Alkali metals belong to Group 1, excluding hydrogen in the usual chemical classification.
They include lithium, sodium, potassium, rubidium, caesium, and francium.
These elements are generally soft, highly reactive metals. They have one valence electron and commonly form +1 ions.
Their reactivity generally increases down the group.
Sodium and potassium are particularly important in biological systems. They help maintain fluid balance and support nerve and muscle functions.
Alkaline Earth Metals
Alkaline earth metals belong to Group 2.
They include beryllium, magnesium, calcium, strontium, barium, and radium.
These elements have two valence electrons and commonly form +2 ions.
Calcium is essential for bones and teeth, while magnesium is important for many biological processes and is also used in lightweight metal alloys.
Transition Metals
Transition metals are generally associated with Groups 3–12.
They often show variable oxidation states and can form colorful compounds.
Examples include iron, copper, nickel, chromium, and zinc.
Transition metals are important in construction, electrical systems, industrial catalysts, machinery, and manufacturing.
Lanthanoids
The lanthanoids are a series of 15 elements, generally from lanthanum to lutetium.
They are often called rare-earth elements, although some are relatively abundant in the Earth’s crust.
Many lanthanoids are used in permanent magnets, electronic devices, display technologies, and specialized optical materials.
Actinoids
The actinoids are a series of 15 elements, generally from actinium to lawrencium.
All actinoids are radioactive.
Some naturally occurring actinoids, such as uranium and thorium, are found in Earth’s crust. Other members are mainly produced artificially.
Certain actinoids have important applications in nuclear science and research.
Important Information Found in an Element’s Box
Each element in the periodic table is represented by a small box containing important information.
Consider carbon as an example.
Atomic Number: 6
The atomic number represents the number of protons in the nucleus of an atom. Carbon has six protons.
Chemical Symbol: C
A chemical symbol is a short representation of an element. Carbon is represented by the symbol C.
Element Name: Carbon
This is the full name of the chemical element.
Atomic Mass: Approximately 12.011 u
The relative atomic mass is based on the weighted average masses of the naturally occurring isotopes of an element. It is commonly displayed as a numerical value in the periodic table.
Group: 14
Carbon belongs to Group 14.
Period: 2
Carbon is located in the second period of the periodic table.
Understanding these details makes it easier to study an element and compare it with other elements.
Periodic Law
The modern periodic table is based on the modern periodic law.
The modern periodic law states:
The physical and chemical properties of elements are periodic functions of their atomic numbers.
This means that when elements are arranged in increasing order of atomic number, similar physical and chemical properties appear at regular intervals.
For example, lithium, sodium, and potassium belong to the same group and show similar chemical behavior.
This periodic repetition occurs because similar valence electron configurations appear at regular intervals in the arrangement of elements.
The periodic law helps scientists understand why elements have particular properties and predict the behavior of elements that have not been studied extensively.
Periodic Trends in the Periodic Table
Periodic trends are predictable changes in the properties of elements across periods and down groups.
These trends help explain the behavior of atoms and their chemical reactions.
Atomic Radius
Atomic radius is a measure of the size of an atom.
Across a period from left to right, atomic radius generally decreases because the nuclear charge increases while electrons are added to the same principal shell.
Down a group, atomic radius generally increases because additional electron shells are added.
Ionization Energy
Ionization energy is the energy required to remove an electron from an isolated gaseous atom.
Across a period, ionization energy generally increases because the effective nuclear attraction on the outer electrons becomes stronger.
Down a group, it generally decreases because the outermost electrons are farther from the nucleus and experience greater shielding.
Electronegativity
Electronegativity describes the ability of an atom to attract shared electrons in a chemical bond.
It generally increases across a period and decreases down a group.
Fluorine is the most electronegative element.
Electron Affinity
Electron affinity refers to the energy change associated with adding an electron to a neutral gaseous atom.
Its trend across the periodic table is not perfectly regular, but many nonmetals have favorable electron-gain behavior.
Halogens generally have high electron affinities.
Metallic Character
Metallic character describes how strongly an element displays metallic properties, including its tendency to lose electrons in chemical reactions.
It generally decreases across a period from left to right and increases down a group.
These trends are useful for comparing elements and predicting their chemical behavior.
Importance and Applications of the Periodic Table
The periodic table is not simply a chart used in chemistry classrooms. It is an important scientific reference that supports research, industrial development, and technological progress.
Understanding Chemical Reactions
The periodic table helps scientists understand how elements react with one another.
For example, Group 1 metals commonly lose one electron, while Group 17 elements commonly gain one electron when forming simple ionic compounds.
This knowledge helps explain the formation of many chemical compounds.
Developing New Materials
Scientists use information about elements and their properties to develop new materials.
For example, silicon is used in semiconductor technology, titanium is used in aerospace applications, and various transition metals are used in strong alloys.
Medicine and Healthcare
Several elements have important medical applications.
Iodine is used in thyroid-related healthcare, iron is essential for hemoglobin, and radioactive isotopes of certain elements are used in medical imaging and treatment.
Electronics and Technology
Modern electronic devices depend on elements with specific electrical and physical properties.
Silicon is essential in semiconductor manufacturing. Lithium is widely used in rechargeable batteries, while rare-earth elements are important in many electronic components.
Environmental Science
The periodic table helps scientists understand the chemical composition of air, water, soil, and living organisms.
It is also useful for studying pollution, toxic metals, nutrient cycles, and environmental chemical reactions.
How to Read and Use the Periodic Table
Learning to use the periodic table becomes easier when you understand its basic arrangement.
Follow these steps:
Find the element by its name or chemical symbol.
Identify its atomic number to determine the number of protons.
Check its atomic mass for information about its average atomic mass.
Identify its group to understand its relationship with other elements.
Identify its period to understand its position in the periodic arrangement.
Check its block and category to learn about its electronic structure and general properties.
Compare its position with nearby elements to recognize periodic trends.
For example, if you want to study magnesium, find Mg in Group 2 and Period 3. Its atomic number is 12, meaning that a neutral magnesium atom contains 12 protons and 12 electrons.
Its position in Group 2 indicates that it has two valence electrons and commonly forms Mg²⁺ ions.
Conclusion
The periodic table is a fundamental tool for understanding chemistry and the properties of matter. It organizes all 118 confirmed chemical elements according to their atomic numbers and reveals important relationships between their atomic structures and chemical behavior.
Its arrangement into groups, periods, and blocks makes it easier to classify elements, recognize periodic trends, and predict chemical reactions. From the highly reactive alkali metals to the relatively unreactive noble gases, each group provides valuable information about the characteristics of its elements.
The periodic table also plays an important role in modern science and technology, including medicine, electronics, material development, environmental research, and industrial chemistry.
By understanding its structure, classifications, and periodic trends, anyone can build a strong foundation in chemistry and better understand the elements that make up the world around us.
FAQs
1. What is the periodic table?
The periodic table is a systematic arrangement of all known chemical elements according to their increasing atomic numbers. It organizes elements into horizontal rows called periods and vertical columns called groups. Elements are placed in specific positions based on their atomic structures and electronic configurations. The periodic table provides important information about each element, including its atomic number, chemical symbol, atomic mass, and chemical properties. It also helps scientists understand similarities between elements, recognize periodic trends, and predict how elements behave during chemical reactions.
2. How many elements are present in the modern periodic table?
The modern periodic table contains 118 confirmed chemical elements. These elements are arranged in increasing order of atomic number, starting with hydrogen (H), which has atomic number 1, and ending with oganesson (Og), which has atomic number 118. Some elements occur naturally, while others have been produced artificially in laboratories and nuclear research facilities. Each element has a unique atomic number and chemical symbol. Scientists continue to study these elements and investigate the possibility of discovering or producing new elements in the future.
3. Who invented the periodic table?
Russian chemist Dmitri Mendeleev is widely recognized for developing one of the earliest successful periodic tables in 1869. He arranged elements mainly according to increasing atomic mass and grouped elements with similar chemical properties together. One of his most important contributions was leaving gaps for elements that had not yet been discovered. He also predicted the properties of these missing elements. Later discoveries confirmed several of his predictions. The modern periodic table was subsequently developed using atomic number, following Henry Moseley’s important research in 1913.
4. What are groups and periods in the periodic table?
Groups and periods describe the arrangement of elements in the periodic table. Groups are the 18 vertical columns, while periods are the seven horizontal rows. Elements in the same group often have similar chemical properties because they have similar valence electron configurations. The period number generally indicates the highest occupied principal electron shell in an element’s ground-state configuration. Moving across a period or down a group reveals predictable changes in atomic radius, ionization energy, electronegativity, and metallic character. These patterns are known as periodic trends.
5. What are the four blocks of the periodic table?
The four blocks of the periodic table are s-block, p-block, d-block, and f-block. They are classified according to the type of atomic orbital that receives the last electron in the ground-state electronic configuration. The s-block mainly contains Groups 1 and 2, the p-block contains Groups 13–18, the d-block contains transition elements, and the f-block includes lanthanoids and actinoids. Each block has characteristic electronic structures and chemical properties. This classification helps scientists understand electron configurations and explain the chemical behavior of different elements.
6. What is the difference between metals, nonmetals, and metalloids?
Metals, nonmetals, and metalloids are three broad categories of chemical elements. Metals generally have good electrical and thermal conductivity, metallic shine, and the ability to lose electrons. Nonmetals are usually poor conductors and often gain or share electrons during chemical reactions. Metalloids have properties intermediate between metals and nonmetals. Silicon and germanium are common examples of metalloids and are important in semiconductor technology. These categories help scientists classify elements and understand their physical properties, chemical behavior, and practical applications.
7. What is the modern periodic law?
The modern periodic law states that the physical and chemical properties of elements are periodic functions of their atomic numbers. This means that when elements are arranged in increasing order of atomic number, similar properties appear at regular intervals. These repeating patterns occur because elements develop similar valence electron configurations at different positions in the periodic table. The modern periodic law forms the scientific foundation of the present periodic table. It helps explain periodic trends, classify elements, and predict their chemical properties and reactions.
8. What is atomic number in the periodic table?
Atomic number is the number of protons present in the nucleus of an atom. It is a fundamental property used to identify and arrange chemical elements in the modern periodic table. Every element has a unique atomic number. For example, hydrogen has atomic number 1, carbon has atomic number 6, and oxygen has atomic number 8. In a neutral atom, the number of electrons is equal to the number of protons. Atomic number determines an element’s identity and plays an important role in understanding its electronic configuration and chemical behavior.
9. What are periodic trends in the periodic table?
Periodic trends are predictable patterns in the physical and chemical properties of elements across periods and down groups. Important periodic trends include atomic radius, ionization energy, electronegativity, electron affinity, and metallic character. For example, atomic radius generally decreases from left to right across a period and increases down a group. Ionization energy generally increases across a period and decreases down a group. These trends are influenced by nuclear charge, electron shielding, and electron-shell structure. Understanding periodic trends helps scientists compare elements and predict their chemical behavior.
10. Why is the periodic table important in chemistry?
The periodic table is important because it provides a systematic way to study and understand chemical elements. It helps students and scientists identify elements, compare their properties, understand electron configurations, and predict chemical reactions. Its arrangement reveals relationships between elements and explains why certain elements show similar chemical behavior. The periodic table is also useful in medicine, electronics, agriculture, environmental science, and material development. By studying the periodic table, scientists can better understand the composition of matter and develop new materials and technologies for practical applications.
