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Modern Periodic Law

  • Difficulty Level : Hard
  • Last Updated : 29 Oct, 2021

All matter in our environment is made up of basic units known as elements. In the beginning, only 31 chemical elements were discovered in 1800. Around 63 more elements were discovered after technological advancements in 1865. This necessitated the periodic classification of elements. There are currently 118 elements known to us. Some of the 118 chemical elements are created by humans.

When there were only 31 elements, studying the properties of these chemical elements individually was relatively simple. With the number of elements now at 118, studying the properties of each element individually would be extremely time-consuming. Scientists began thinking about a method to simplify the study of elements in order to make their work easier. They decided to arrange the elements in a periodic table based on the information available about the elements and the various properties they exhibit.

Elements’ properties have been observed to have periodicity. To study the properties of elements in a fixed pattern, many tables were created to arrange the elements in an ordered manner based on their characteristics.

Significance of the Periodic Classification of Elements

  • The classification of elements into groups provides us with a fixed pattern in which the elements’ properties change on a regular basis. The periodic table simplified and organised the study of elements’ physical and chemical properties. We can now simply go to the group and see the properties of the periodic table elements or predict the properties of an element if we know the properties of other elements in the same group.
  • Despite the fact that so many elements have already been discovered, there is still a chance that new elements will be discovered. Scientists can use a periodic table to learn about the trending characteristics of elements based on their properties, and thus distinguish new elements from existing ones. Furthermore, researchers are constantly striving to discover new elements and investigate their properties.

Modern Periodic Law

The modern periodic table is based on Mendeleev’s periodic law and the periodic table. Mendeleev created his periodic table in the late 18th century. Back then, scientists had no idea about the internal structure of the atom. The advancement of quantum theory and the development of various atomic models revealed that the atomic number is the most fundamental property of a chemical element. This resulted in the modification of Mendeleev’s periodic law, now known as modern periodic law. Modern Periodic law can be stated as follows:

Elements’ physical and chemical properties are periodic functions of their atomic numbers.

where the atomic number is the number of electrons or protons in a neutral atom. Scientists now had a clear understanding of quantum numbers and the electronic configuration of elements in the periodic table after learning about the fundamental unit of elements. Chemists discovered an analogy between the 94 naturally occurring chemical elements after learning about the periodic law. This analogy piqued people’s interest in the chemistry of these elements. Scientists created a variety of artificial elements. By modifying Mendeleev’s periodic table, a new periodic table based on modern periodic law was created.

Modern Periodic Table

The long form of the periodic table is the current form that is widely used around the world. The horizontal rows are known as periods in this form of a periodic table, and the vertical columns are known as groups. Groups are made up of elements that have atoms with similar outer shell electronic configurations. 

The groups are labelled as 1, 2, 3, and so on. Periods are the seven horizontal rows of the modern periodic table. The period of the element is determined by the quantum number n. One of the four quantum numbers is the principal quantum number (n) (n, l, m, and s). It informs us about the fundamental electron shell. For example, if n=3, the principle shell is indicated as 3.

Classification of the Elements in the Periodic Table

  1. Noble gas elements: Noble gases are elements from group 18 of the modern periodic table. Because the octet of these elements is complete, they are extremely stable.
  2. Representative elements: S-block and P-block elements are examples of representative elements. The elements in groups 1 and 2 are referred to as s – block elements. The p-block elements are those in groups 13-17.
  3. Transition elements: Transition elements are elements that belong to groups 3 to 12. These elements are also referred to as d-block elements.
  4. Inner transition elements: The inner transition elements are the lanthanides and actinides series, which are found at the bottom of the periodic table. Some orbitals in these elements are partially filled, giving them unique properties.

The number of elements in each period:

  • The first period has 2 elements.
  • The second period has 8 elements.
  • The third period has 8 elements.
  • The fourth period has 18 elements.
  • The fifth period has 18 elements.
  • The sixth period has 32 elements.
  • The seventh period has the rest of the elements.

Sample Questions

Question 1: What was the need for the classification of elements?

Answer:

The process of categorizing elements into different classes is known as periodic element classification. This method entails the arrangement of related elements as well as the separation of unlike elements. Elements’ properties are compared. It aids us in understanding how different compounds combine to form different elements.

Question 2: What are the advantages of the classification of elements?

Answer:

Chemists can predict the properties of elements and their compounds in the periodic table based on their positions, and vice versa. It becomes easier to study, comprehend, compare, and contrast the relative properties of elements and their compounds from various groups.

Question 3: What are the two types of alloys?

Answer:

There are two types of alloys. Interstitial alloys and substitutional alloys are the terms for these. The atoms of the original metal are essentially substituted by atoms of a similar size from another element in substitute alloys. Brass, for example, is a copper and zinc replacement alloy.

Problem 4: Who gave the modern periodic law?’

Answer:

Dmitri Mendeleev and Lothar Meyer independently established the periodic law in 1869. Mendeleev created the first periodic table, which was quickly followed by Meyer. Each grouped the elements based on their mass and proposed that those properties reoccur on a regular basis.

Question 5: Is atomic mass a periodic property?

Answer:

Nuclear mass generally decreases from left to right and always increases from top to bottom. Because the atomic number was developed as the foundation for organizing the elements on the periodic table, it will always increase from left to right and top to bottom.

Question 6: Define relative periodic property?

Answer:

The valence shell electronic configuration of any two elements during a given period is not the same. As a result, elements have different chemical properties over time, with a periodic gradation from left to right for their physical properties. This is known as the periodic property.

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