(ATPT) Trends on the Periodic Table Lesson

Trends on the Periodic Table

The wonderful thing about the periodic table is that it's periodic! There are many patterns that can be found within the periodic table that can help understand the chemistry and interactions of different elements at a glance. These trends reduce the need for memorization of these characteristics. Instead, you should understand how these trends work, which is what this lesson will cover.

We have talked in great detail about how the periodic table was developed, but we have yet to talk about where the periodic table gets its name. To be periodic means to "have repeating cycles" or repeating patterns. In the periodic table, there are a number of physical properties that are "trend-like". What this means is that as you move down a group or across a period, you will see the properties changing in a general direction.

The periodic table is a powerful tool that provides a way for chemists to organize the chemical elements. The word "periodic" means happening or recurring at regular intervals. The periodic law states that when elements are arranged in order of increasing atomic number, there is a periodic repetition of their chemical and physical properties. The electron configurations of the atoms vary periodically with their atomic number. Because the physical and chemical properties of elements depend on their electron configurations, many of the physical and chemical properties of the elements tend to repeat in a pattern.

One general trend that we have already observed is in regard to metals and nonmetals. Look at the picture below for review. We can see that the further down a given group, the elements have an increased metallic character: they are good conductors of both heat and electricity, solids at room temperature, and shiny in appearance. Moving from left to right across a period, the elements have greater non-metallic character. These elements are insulators, poor heat conductors, and can exist in different phases at room temperature (brittle solid, liquid, or gas). The elements at the boundary between the metallic elements (grey elements) and nonmetal elements (green elements) are metalloid in character (pink elements). They have low electrical conductivity that increases with temperature. They also share properties with both the metals and the nonmetals.

main elements on a periodic table with metals, nonmetals, and metalloids color coded

Definitions and Important Concepts

Before we can talk about the trends in the periodic table in more detail, we first need to define some terms that are used:

  • Atomic radius - The atomic radius is a measure of the size of an atom.
  • Ionization energy - The energy required to remove the most loosely held electron from an atom in the gas phase. The higher the value of the ionization energy, the harder it is to remove that electron.
  • Electronegativity - Electronegativity is the tendency of atoms to attract electrons. The values of electronegativity are higher for elements that more strongly attract electrons.

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