The 7 Periods Of The Periodic Table

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A period on the periodic table is a row of chemical elements. All elements in a row have the same number of electron shells. Each next element in a period has one more proton and is less metallic than its predecessor. Arranged this way, elements in the same group (column) have similar chemical and physical properties, reflecting the periodic law. For example, the halogens lie in the second-to-last group (group 17) and share similar properties, such as high reactivity and the tendency to gain one electron to arrive at a noble-gas electronic configuration. As of 2022[update], a total of 118 elements have been discovered and confirmed.

Modern quantum mechanics explains these periodic trends in properties in terms of electron shells. As atomic number increases, shells fill with electrons in approximately the order shown in the ordering rule diagram. The filling of each shell corresponds to a row in the table.

In the s-block and p-block of the periodic table, elements within the same period generally do not exhibit trends and similarities in properties (vertical trends down groups are more significant). However, in the d-block, trends across periods become significant, and in the f-block elements show a high degree of similarity across periods.

There are currently seven complete periods in the periodic table, comprising the 118 known elements. Any new elements will be placed into an eighth period; see extended periodic table. The elements are colour-coded below by their block: red for the s-block, yellow for the p-block, blue for the d-block, and green for the f-block.

The first period contains fewer elements than any other, with only two, hydrogen and helium. They therefore do not follow the octet rule, but rather a duplet rule. Chemically, helium behaves like a noble gas, and thus is taken to be part of the group 18 elements. However, in terms of its nuclear structure it belongs to the s-block, and is therefore sometimes classified as a group 2 element, or simultaneously both 2 and 18. Hydrogen readily loses and gains an electron, and so behaves chemically as both a group 1 and a group 17 element.

Period 4 includes the biologically essential elements potassium and calcium, and is the first period in the d-block with the lighter transition metals. These include iron, the heaviest element forged in main-sequence stars and a principal component of the Earth, as well as other important metals such as cobalt, nickel, and copper. Almost all have biological roles.

Period 5 has the same number of elements as period 4 and follows the same general structure but with one more post transition metal and one fewer nonmetal. Of the three heaviest elements with biological roles, two (molybdenum and iodine) are in this period; tungsten, in period 6, is heavier, along with several of the early lanthanides. Period 5 also includes technetium, the lightest exclusively radioactive element.

Period 6 is the first period to include the f-block, with the lanthanides (also known as the rare earth elements), and includes the heaviest stable elements. Many of these heavy metals are toxic and some are radioactive, but platinum and gold are largely inert.

All elements of period 7 are radioactive. This period contains the heaviest element which occurs naturally on Earth, plutonium. All of the subsequent elements in the period have been synthesized artificially. Whilst five of these (from americium to einsteinium) are now available in macroscopic quantities, most are extremely rare, having only been prepared in microgram amounts or less. Some of the later elements have only ever been identified in laboratories in quantities of a few atoms at a time.

No element of the eighth period has yet been synthesized. A g-block is predicted. It is not clear if all elements predicted for the eighth period are in fact physically possible. There may therefore be no ninth period.

A group is a vertical column of the periodic table, based on the organization of the outer shell electrons. There are a total of 18 groups. There are two different numbering systems that are commonly used to designate groups, and you should be familiar with both. The traditional system used in the United States involves the use of the letters A and B. The first two groups are 1A and 2A, while the last six groups are 3A through 8A. The middle groups use B in their titles. Unfortunately, there was a slightly different system in place in Europe. To eliminate confusion, the International Union of Pure and Applied Chemistry (IUPAC) decided that the official system for numbering groups would be a simple 1 through 18 from left to right. Many periodic tables show both systems simultaneously.

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In this tutorial, you will learn how to read the periodic table. We will take a close look at the groups of the periodic table. In addition, you will learn about the different properties of the periodic table groups, periods, and families. If you enjoy this article, be sure to check out our others!

We think our periodic table is one of the best in the world! Visit our new interactive periodic table. You can view all sorts of trends, properties, magnetism, electrons, and even articles on all the elements!

So what is a period on the periodic table? Periods are the horizontal rows of the periodic table. There are seven periods total and each element in a period has the same number of atomic orbitals. The top period, which contains hydrogen and helium, has only two orbitals. As you go down the rows, the number of orbitals increases. Below is a table to help visuals the periodic number and the corresponding orbitals.

The number of valence electrons present dictates the properties of an element. The reason for this is that the valence electrons, which are the electrons in the outermost shell, are the ones taking part in chemical reactions. These electrons are either donating, accepting, or sharing. Moreover, the more filled the valence shell is, the more stable the element.

The first group is the least stable as it only has one valence electron. Meanwhile, group eighteen is the most stable as these elements have a full valence shell (eight valence electrons). Below is a table relating the group numbers to the number of valence electrons.

On the periodic table, there are families which are groups of elements with similar properties. These families are alkali metals, alkaline earth metals, transition metals, post-transition metals, metalloids, halogens, noble metals, and noble gases. Many of these families belong to a single group on the periodic table. However, not all of the families overlap with periodic table groups. For example, the transition metals contain all elements from group three to group twelve. Below is a periodic table where displaying the location of each family. You can also get a tutor to learn more about the table and see examples of several real elements.

The alkali metals consist of all of the elements in group one with the exception of hydrogen. These elements are extremely reactive and for this reason, are usually found in compounds. In addition, they are water-sensitive (they react violently with water), so they must be stored in oil. The most reactive alkali metal is francium and it decreases as you go up the group. This means lithium is the least reactive. Physically, the alkali metal family is silvery, white, and light. They also have low melting and low boiling points.

The alkaline earth metals are the second most reactive family on the periodic table (following behind the alkali metals). Moreover, they are strong reducing agents which means they donate electrons in chemical reactions. They are also good thermal and electrical conductors. Physically, they have low density, low melting point, and a low boiling point.

Lanthanides are a family of rare earth metals that contain one valence electron in the 5d shell. They are highly reactive and a strong reducing agent in reactions. Furthermore, they are a silvery-bright metal and are relatively soft. They also have both high melting points and high boiling points. The rare earths include elements like neodymium and erbium.

Actinides are another family of rare earth metals. Like the lanthanides, these elements are highly reactive. They also have high electropositivity and are radioactive. Additionally, these elements contain paramagnetic, pyromorphic, and allotropic properties. Physically, they are very similar to lanthanides. They are silvery metals that are soft, malleable, and ductile.

The transition metals typically form two or more oxidation states. They have low ionization energies and high conductivity. In addition, they have high melting points, high boiling points, and high conductivity. Physically they are both metallic and malleable.

The post transition metals are located in between the transition metals and the metalloids. At standard temperature, they are in a solid state of matter. They tend to have a high density as well as high conductivity. Physically they are malleable and ductile.

The metalloids display properties of both metals and non-metals. For example, metals are good conductors and non-metals are poor conductors. This means metalloids are semiconductors (only conducts electricity at high temperatures.). Also, they are more brittle than metals but less brittle than non-metals. Physically they can be either shiny or dull and are typically ductile and malleable.

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