Introduction

The Periodic table consists of all of the known elements scientists have discovered. It is arranged in a way that is easy for us to understand, using the atomic number and properties. 

The atomic number is the amount of protons and electrons in the element- which can tell us how many energy levels there are, how many valence electrons there are, and how they tend to react with other elements. From left to right there are alkali earth metals, transition metals, rare earth metals, metalloids, nonmetals, halogens, and noble gasses

Periodic trends are specific patterns that are present in the periodic table that illustrate different aspects of a certain element, including its size and its electronic properties. 

The three major periodic trends we will be discussing are electronegativity, atomic radius, and ionization energy (below).

Ionization energy

On the periodic table ionization energy decreases when going from top to bottom, and increases from left to right. In other words, from the bottom left to the top right of the periodic table, ionization energy increases.

Ionization energy is the amount of energy required to remove electrons from an atom.

Electronegativity

Just like ionization energy, electronegativity decreases down a group and increases across a period. Unlike 

ionization energy, 

electronegativity's 

trend does not 

apply to the noble 

gases on the far right 

of the periodic table.

Electronegativity is the measure of the ability of an atom to attract electrons to itself.

Atomic Radius

It's trend differs from the others. Atomic radius decreases both from left to right and top to bottom.

Atomic radius is described as the measure of the size of an atom. It is calculated by measuring the distance from the atom's nucleus to the outer edge of the electron cloud.

How To Analyze All 3 Trends in the periodic table:

Looking at the periodic table, each trend increases and decreases in a certain direction, left to right or up to down.

Atomic radius decreases across a period from left to right and increases from top to bottom.

Atomic Radius

Atomic radius decreases across the period because a higher effective nuclear charge causes greater attractions to the electrons, pulling the electron cloud closer to the nucleus which results in a smaller atomic radius. Atomic radius increases down a group because there are more energy levels being added to the atom.

If you observe the periodic table, you can see that ionization energy increases from left to right and decreases down a group.

Ionization Energy

Ionization energy increases across a period because it pulls the electron cloud closer to the nucleus, strengthening the nuclear attraction to the outermost electron, and is much more difficult to remove. Ionization energy decreases down a group because the number of energy levels increases and the distance increases between the nucleus and the outer shell so this distance weakens the nuclear attraction and makes it easier to remove an electron.