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The Royal Society of Chemistry's interactive periodic table features history, alchemy, podcasts, videos, and data trends across the periodic table. Click the tabs at the top to explore each section. Use the buttons above to change your view of the periodic table and view Murray Robertson's stunning Visual Elements artwork. Click each element to read detailed information.

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Periodic Table - Royal Society of Chemistry

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Interactive periodic table with element scarcity (SRI), discovery dates, melting and boiling points, group, block and period information.

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© 2000-2018 Sandbox Networks, Inc., publishing as Infoplease

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Pictures, stories, and facts about the element Hydrogen in the Periodic Table

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Photographs and descriptions of many samples of the element Hydrogen in the Periodic Table.

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How To Read the Periodic Table of the Elements

Click on an element symbol to get detailed facts about each chemical element. The element symbol is a one- or two-letter abbreviation for an element's name.

The integer number above the element symbol is its atomic number. The atomic number is the number of protons in every atom of that element. The number of electrons can change, forming ions, or the number of neutrons can change, forming isotopes, but the proton number defines the element. The modern periodic table orders the element by increasing atomic number. Mendeleev's periodic table was similar, but the parts of the atom weren't known in his day, so he organized elements by increasing atomic weight.

The number below the element symbol is called the atomic mass or the atomic weight. It's the sum of the mass of protons and neutrons in an atom (electrons contribute negligible mass), but you may notice it isn't the value you'd get if you assumed the atom had an equal number of protons and neutrons.

The atomic weight values may be different from one periodic table to another because it's a calculated number, based on the weighted average of the natural isotopes of an element. If a new supply of an element is discovered, the isotope ratio may be different from what scientists previously believed.

Then, the number may change. Note, if you have a sample of a pure isotope of an element, the atomic mass is simply the sum of the number of protons and neutrons of that isotope!

Element Groups and Element Periods

The periodic table gets its name because it arranges the elements according to recurring or periodic properties. The groups and periods of the table organize elements according to these trends. Even if you didn't know anything about an element, if you knew about one of the other elements in its group or period, you could make predictions about its behavior.

Groups

Most periodic tables are color-coded so that you can see at a glance which elements share common properties with each other. Sometimes these clusters of elements (e.g., alkali metals, transition metals, non-metals) are called element groups, yet you'll also hear chemists refer to the columns (moving top to bottom) of the periodic table called element groups. Elements in the same column (group) have the same electron shell structure and the same number of valence electrons. Since these are the electrons that participate in chemical reactions, elements in a group tend to react similarly.

The Roman numerals listed across the top of the periodic table indicate the usual number of valence electrons for an atom of an element listed below it.

For example, an atom of a group VA element will typically have 5 valence electrons.

Periods

The rows of the periodic table are called periods. Atoms of elements in the same period have the same highest unexcited (ground state) electron energy level. As you move down the periodic table, the number of elements in each group increases because there are more electron energy sublevels per level.

Periodic Table Trends

In addition to the common properties of elements in groups and periods, the chart organizes elements according to trends in ionic or atomic radius, electronegativity, ionization energy, and electron affinity.

Atomic radius is half the distance between two atoms that are just touching. Ionic radius is half the distance between two atomic ions that are barely touching. Atomic radius and ionic radius increase as you move down an element group and decrease as you move across a period from left to right.

Electronegativity is how easily an atom attracts electrons to form a chemical bond. The higher its value, the greater the attraction for bonding electrons. Electronegativity decreases as you move down a periodic table group and increases as you move across a period.

The energy needed to remove an electron from a gaseous atom or atomic ion is its ionization energy. Ionization energy decreases moving down a group or column and increases moving from left to right across a period or row.

Electron affinity is how easily an atom can accept an electron. Except that the noble gases have practically zero electron affinity, this property generally decreases moving down a group and increases moving across a period.

The Purpose of the Periodic Table

The reason chemists and other scientists use the periodic table rather than some other chart of element information is because the arrangement of elements according to periodic properties helps predict properties of unfamiliar or undiscovered elements. You can use the location of an element on the periodic table to predict the types of chemical reactions it will participate in and whether or not it will form chemical bonds with other elements.

Printable Periodic Tables and More

Sometimes it's helpful to print out a periodic table, so you can write on it or have it with you anywhere. I've got a large collection of periodic tables you can download to use on a mobile device or print. I've also got a selection of periodic table quizzes you can take to test your understanding of how the table is organized and how to use it to get information about the elements.

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Look Up Element Facts on the Clickable Periodic Table

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Click on an element symbol to get detailed facts about each chemical element. The element symbol is a one- or two-letter abbreviation for an element's name. The integer number above the element symbol is its atomic number. The atomic number is the number of protons in every atom of that element.

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The Periodic Table of Elements

Download a printable version of the Periodic Table of Elements in PDF format:

- Black and White: Basic / Advanced

The following on-line games based on the Periodic Table of Elements are available:

- Element Flash Cards

- Element Hangman

- Element Matching

- Element Math

- Element Crossword Puzzles

- Element Concentration

- Element Balancing

- Element Word Scramble

The following paper-based activities are available:

- Element BINGO

- Element Word Search

In addition to the information contained within the Periodic Table of Elements, the following articles may be helpful if you are writing a report about an element or if you are making a model of an atom:

- How to calculate the number of protons, neutrons and electrons in an atom of an element

- How to make a model of an atom

- How to draw an atom (video)

- How to read an electron configuration chart

- A list of who discovered each element

The information on this site has been compiled from a number of sources.

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The Periodic Table of Elements Download a printable version of the Periodic Table of Elements in PDF format: - Black and White: Basic / Advanced The following on-line games based on the Periodic Table of Elements are available: - Element Flash Cards - Element Hangman - Element Matching - Element

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The periodic table of the elements by WebElements

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Explore atom properties of the chemical elements through this periodic table

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Periodic Table Key

The periodic table we use today is based on the one devised and published by Dmitri Mendeleev in 1869.

Mendeleev found he could arrange the 65 elements then known in a grid or table so that each element had:

1. A higher atomic weight than the one on its left. For example, magnesium (atomic weight 24.3) is placed to the right of sodium (atomic weight 23.0):

The True Basis of the Periodic Table

In 1913, chemistry and physics were topsy-turvy. Some big hitters - including Mendeleev - were talking seriously about elements lighter than hydrogen and elements between hydrogen and helium. Visualizing the atom was a free-for-all, and Mendeleev's justification for a periodic table based on atomic weights was falling apart at the seams.

This is the story of how Henry Moseley brought light to the darkness.

2. Similar chemical properties to other elements in the same column - in other words similar chemical reactions. Magnesium, for example, is placed in the alkali earths' column, with other elements whose reactions are similar:

Mendeleev realized that the table in front of him lay at the very heart of chemistry. And more than that, Mendeleev saw that his table was incomplete - there were spaces where elements should be, but no-one had discovered them.

Just as Adams and Le Verrier could be said to have discovered the planet Neptune on paper, Mendeleev could be said to have discovered germanium on paper. He called this new element eka-silicon, after observing a gap in the periodic table between silicon and tin:

Similarly, Mendeleev discovered gallium ( eka-aluminum) and scandium ( eka-boron) on paper, because he predicted their existence and their properties before their actual discoveries.

Although Mendeleev had made a crucial breakthrough, he made little further progress. With the benefit of hindsight, we know that Mendeleev's periodic table was underpinned by false reasoning. Mendeleev believed, incorrectly, that chemical properties were determined by atomic weight. Of course, this was perfectly reasonable when we consider scientific knowledge in 1869.

In 1869 the electron itself had not been discovered - that didn't happen for another 27 years.

In fact, it took all of 44 years for the correct explanation of the regular patterns in Mendeleev's periodic table to be found...

Read More... The Periodic Table continued

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Periodic Table of Elements and Chemistry

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Award winning periodic table with user-friendly element data and facts. Cool online chemistry videos, dictionary, tools, etc.