# How The Horizontal Rows In The Periodic Table Are Organized

The periodic table is one of the most important tools for chemists and other scientists who study the elements and the way they interact. It provides a convenient way to organize and visualize the way the elements interact, and it is an invaluable resource for understanding the behavior of matter. The periodic table is divided into many different sections, including the vertical columns and the horizontal rows. In this article, we will take a closer look at how the horizontal rows in the periodic table are organized.

## The Periodic Table of Elements

The periodic table is a chart that lists all of the elements known to man. It was first created by chemist Dmitri Mendeleev in 1869 and is one of the most important tools for chemists and other scientists. It arranges the elements according to their atomic number, which is the number of protons in each element’s atom. The table is divided into seven horizontal rows, which are called periods. Each period contains elements with similar properties because they have the same number of electrons in their outer shell.

### Periods in the Periodic Table

The seven periods in the periodic table are numbered one through seven, starting at the top of the table and going down. Each period contains elements with similar properties because they have the same number of electrons in their outer shell. Periods one and two contain two elements, period three contains eight elements, period four contains eighteen elements, period five contains thirty-eight elements, period six contains sixty-two elements, and period seven contains eighty-four elements. As you move from left to right across the table, the elements become increasingly electronegative, meaning they are more likely to form chemical bonds with other elements.

### Grouping of Elements

Within each period, the elements are further divided into groups. Each group is identified by a number and a letter. The group number indicates the number of electrons in the outer shell of the element. Group one, for example, contains elements with one electron in their outer shell, while group two contains elements with two electrons in their outer shell. The letter indicates the type of element. Group A is composed of non-metals, group B is composed of metals, group C is composed of metalloids, and group D is composed of transition metals. The elements within each group tend to have similar properties, which makes them easier to classify and understand.

### Trends in the Periodic Table

When moving from left to right across a period, certain trends can be observed. Generally, the elements become more electronegative and reactive. That means that as you move from left to right, the elements become more likely to form chemical bonds with other elements. Also, the number of electrons in the outer shell increases as you move from left to right. This means that elements on the right side of the periodic table are more likely to gain electrons and form negative ions.

### The Lanthanides and Actinides

The lanthanides and actinides are two groups of elements that are often grouped together and located at the bottom of the periodic table. These elements, which are also known as “rare earth elements,” are not found in nature in their pure form and must be extracted from ores. The lanthanides are considered to be chemical elements, while the actinides are considered to be radioactive elements. Both groups contain elements with similar chemical and physical properties and are often used in industrial and medical applications.

### Conclusion

The horizontal rows in the periodic table are an important way to organize the elements and understand their behavior. The elements in each period are organized according to their atomic number, and the elements in each group have similar properties. The lanthanides and actinides are two groups of elements that are often grouped together and located at the bottom of the table. By understanding the organization of the horizontal rows in the periodic table, scientists and chemists can better understand the behavior of the elements.