How Many Periods are There in Modern Periodic Table

Introduction

There are 7 periods in the modern periodic table. The periodic table was originally developed by Mendeleev in 1869. He made a tabular diagram of known elements and group them based on atomic weight. In his chart, he allotted some space for elements yet to be discovered.

Many new elements have been discovered since then. Also few elements have been made up in the laboratory. In the modern periodic table, elements are arranged based on their atomic number. So that the elements with the same property come under the same group or horizontal column. In total there are eighteen vertical groups and seven horizontal periods.

Properties of 1st period

The first period consisting of hydrogen, 1, and helium, 2, is also known as the hydrogen period. Since they have lower atomic numbers they don't follow octet rules they follow duplet rules. Helium shows chemical properties the same as Noble elements and thus it is considered a part of group 18.

• Hydrogen (H) is the most found chemical element in the universe comprising roughly 75% of the universe's element mass. Hydrogen is present in water and most organic compounds since it can easily form compounds with most of the elements.

• Helium (He) is the second most found element in the universe and the second lightest element. It is present in the form of gas.

Properties of 2nd period

The second period consists of lithium, beryllium, Boron, Carbon, Nitrogen, Oxygen fluorine, and neon. Carbon, Nitrogen, and Oxygen are the most biologically Essential elements present in this group.

• Lithium (Li) is the lightest metal. It is one of the most reactive elements when it is in a non-ionized state.

• Beryllium (Be) has one of the highest melting points among light metals. It comes under alkaline earth metals.

• Boron (B) does not occur as a free element but is found in compounds like borates. High levels of boron are toxic though they come under essential plant micronutrient

• Carbon (C) forms long stable chain compounds with another element that separates it from all the other elements in the periodic table.

• Nitrogen (N) is present mostly in the form of inert diatomic gas.

• Oxygen (O) is the third most abundant element in the universe and oxygen compounds dominate Earth's crust.

• Fluorine (F) in its non-ionized state is the most reactive element.

• Neon (Ne) is a noble gas.

Properties of 3rd period

Except for the noble gas Argon, all period three elements occur in nature. The third period consists of sodium, magnesium aluminum Silicon Phosphorus Sulphur chlorine, and Argon.

Properties of 4th period

The fourth period consists of some biologically important elements like potassium and Calcium. It also consists of some important metals such as Cobalt Nickel Copper and iron.

Properties of 5th period

The fifth period consists of the two heaviest elements with biological importance molybdenum and Iodine.

Properties of 6th period

The sixth period comprises rare Earth elements and also includes the heaviest stable elements.

Properties of 7th period

All elements present in the seventh period are Radioactive. Most of the elements are extremely rare and can only be prepared in the laboratory in lesser amounts.