Some things are very heavy.
These are special parts of our world. They are very rare. They can even glow blue.
Most of them are made in labs. Do you like science?
Scientists use a chart to group parts of our world.
The seventh row has 32 parts. All of these parts are radioactive. This means they give off energy.
Some parts are found in nature. For example, uranium is found in the ground. Other parts must be made in labs.
Some parts are very rare. Some exist as only a few tiny atoms. One part even glows a faint blue.
These parts help us learn about science.
The periodic table is a chart of all known elements. It uses rows to show how elements act. The seventh row is called a period. This period has 32 elements.
All elements in this row are radioactive. This means they give off energy as they decay. Some are found in nature. For example, uranium and thorium are in the ground. Other elements are synthetic. This means scientists must make them in a lab.
Some elements are very rare. Scientists may only make a few atoms at a time. These are called transactinides. They are the heaviest elements. Oganesson is the heaviest one we know.
Other elements in this row are called actinides. This group includes plutonium. Most actinides must be made by people. However, americium is used in smoke detectors.
Some elements have special traits. Radium is a white metal. It can glow with a faint blue light. Marie and Pierre Curie discovered it in 1898. Francium is also in this row. It is very rare in the Earth's crust. Only about 20 to 30 grams exist at any time.
The seventh period of the periodic table is a very special row. This row contains 32 different chemical elements.
It is tied with the sixth period for having the most elements. The elements in this row follow a specific order. They fill their 7s shells first, then their 5f, 6d, and 7p shells. This pattern helps scientists understand how they will behave. Some elements, like uranium, are exceptions to this rule.
Every single element in the seventh period is radioactive. This means they release energy as they decay. Some elements, like thorium and uranium, are found naturally in the Earth. Most others must be made by people in a laboratory. These man-made elements are called synthetic elements.
Some of these are very rare. Scientists might only make a few atoms at a time. These super-heavy elements are known as transactinides. They are the heaviest elements we have ever found.
History shows us how these elements were found. Marguerite Perey discovered francium in France in 1939. It was the last element found in nature. Marie and Pierre Curie discovered radium in 1898. They found it in a mineral called uraninite. Later, Marie Curie and André-Louis Debierne isolated radium as a metal in 1910.
Scientists like Glenn T. Seaborg also helped. He proposed the idea of the actinide series. The element seaborgium was even named to honor him.
There are many interesting numbers to know about these elements. Period 7 starts with francium and ends with oganesson. Only about 20 to 30 grams of francium exist in the Earth's crust at any time. Radium-226 is a stable isotope with a half-life of 1601 years. In nature, you might find only a seventh of a gram of radium in a ton of uraninite.
Some synthetic elements are only made in tiny amounts. Scientists sometimes work with just a few micrograms. Other times, they only identify a few atoms at once.
You can see these elements working in your own life. Americium is a part of most modern smoke detectors.
Uranium and thorium are used in nuclear reactors. Radium has a special trait where it glows with a faint blue light. This happens because it is unstable. Some elements are also used in nuclear weapons. Even though these elements are hard to find, they help us understand the physical world.
The seventh period of the periodic table contains a collection of 32 chemical elements.
This row is tied with period 6 for containing the most elements. In a periodic table, rows are called periods. These rows show recurring trends in how elements behave as their atomic number increases. A new row begins when chemical behavior starts to repeat. This means elements with similar behaviors fall into the same vertical columns. The elements in period 7 follow a specific pattern of electron shell filling. They generally fill their 7s shells first. Then, they fill their 5f, 6d, and 7p shells in that order. However, some elements like uranium are exceptions to this rule.
Every single element in the seventh period is radioactive. This means they are unstable and release energy as they decay. The period is divided into different groups, such as the s-block, the actinides, and the transactinides. The s-block includes francium and radium. The actinide series consists of 15 metallic elements from actinium to lawrencium. The transactinide elements, also called superheavy elements, have atomic numbers greater than 103.
These superheavies are all synthetic, meaning they must be created in a laboratory. They are the heaviest elements currently discovered, ending with oganesson. Because they are so heavy, their properties can be very different from what scientists expect.
Let us look closer at the mechanism of how these elements are organized. The arrangement depends on how electrons fill their shells. For most period 7 elements, the order of filling follows the Madelung rule. This rule dictates the sequence of the 7s, 5f, 6d, and 7p shells. However, the massive nuclei of these elements create unique physical effects. The very high electric charge of the nucleus causes relativistic effects and spin-orbit coupling. These forces change how the electrons behave. Because of these effects, the actinides show a much wider variety of oxidation states than the lanthanides. This means they can react in many different ways compared to the elements in the row above them.
History shows how we discovered these remarkable substances. Marguerite Perey discovered francium in France in 1939. It was the last element discovered in nature rather than through synthesis. Marie and Pierre Curie discovered radium in 1898. They extracted it from a mineral called uraninite. Five days after their discovery, they published their findings at the French Academy of Sciences. Later, in 1910, Marie Curie and André-Louis Debierne isolated radium as a metal through electrolysis.
Another important figure was Glenn T. Seaborg. He proposed the concept of the actinide series. To honor his work, the element seaborgium was named after him.
Specific numbers help us understand how rare these elements are. Francium is extremely scarce in the Earth's crust. Only about 20 to 30 grams of it exist at any given time. Most other period 7 elements are much harder to find. While the first five synthetic actinides are available in macroscopic quantities, most others are rare. Some have only been prepared in amounts of one microgram or less. The transactinide elements are even more elusive. Scientists often identify them in laboratories in batches of only a few atoms at a time. Even the longest-lived isotopes of many transactinides have half-lives measured in seconds or even less.
There are many surprising facts about how these elements appear. Radium is an almost pure-white metal, but it reacts with nitrogen in the air to turn black. Because it is so unstable, radium luminesces, which means it glows with a faint blue light.
In nature, radium is found in very tiny amounts. You might find as little as a seventh of a gram in a ton of uraninite. In the case of the transactinides, they are all named after scientists or important locations. This is because they are entirely man-made and do not exist naturally in large amounts.
These elements connect to many important parts of our world. Some actinides, like uranium and thorium, are used in nuclear reactors. Others, like plutonium, are used in nuclear weapons.
Even common household items use these elements. For example, the element americium is used in the ionization chambers of most modern smoke detectors. Studying these heavy elements helps scientists understand the fundamental laws of physics. They help us see how extreme electric charges and massive nuclei change the very nature of matter.
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