What are trends in the periodic table?

Certain properties, such as electronegativity, show a regular similarity in the periodic table after regular intervals. They show patterns of gradual variation in the rows and columns of the periodic table. These properties are called the periodic properties, and this phenomenon is called the periodicity of elements, and commonly referred to as the periodic table trends.

What does periodicity of elements (aka periodic table trends) do?

Periodic table trends occur in the rows and columns of the periodic table. Elements in the periodic table show similarities in their properties (such as electronegativity) after regular intervals. This phenomenon, also known as the chemical periodicity, can be explained by the help of an example:

Electronegativity is a property of elements that indicates the non metallic nature of the elements. In the periodic table, the electronegativities of elements of the seventeenth group (the halogen family of elements) are all high, thus making all of these elements strong non metals. Furthermore, when we move across a row from left to right in the periodic table, the electronegativity of elements increases till the seventeenth group, and when we move down a group of the periodic table, the electronegativities of elements decreases till the 7^th row. Thus, we can see a regular repetition and gradual variation in the electronegativity of elements in the periodic table. This periodic trend is the phenomenon of periodicity of elements.

Apart from electronegativity, there are other periodic properties that follow the phenomenon of periodicity of elements in the periodic table. These properties are :

• atomic size (atomic radius)
• electronegativity
• electron affinity
• ionization energy

Trends of periodic properties in the periodic table are explained in following questions:

• How does atomic size of elements vary in the periodic table?
• How does electronegativity vary on moving across the row and down the columns of the periodic table?