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Classification of Elements

  • Last Updated : 27 Sep, 2021

Periodic categorization of elements is a way of grouping elements based on their characteristics, such as keeping elements that are similar in one group and the rest of the elements in the other. The elements are grouped in the long-form periodic table in order of their atomic numbers. The atomic number of an element is equal to the number of protons inside the nucleus of its atom. The long-form periodic table has the following characteristics:

  • The long-form periodic table has 18 vertical columns and 18 groups in total.
  • Beginning on the left, these groups are numbered 1 through 18.
  • In a long-form periodic table, there are seven horizontal rows known as periods. In the long-form periodic table, this results in seven periods.
  • The main group elements are those found in Groups 1, 2, and 13–17. These elements are also referred to as a typical, representative, or normal elements.
  • The elements of Groups 3 to 12 are called transition elements.
  • Lanthanides are elements with atomic numbers 58 to 71 (Ce to Lu) that exist after lanthanum (La). Actinides are elements with atomic numbers 90 to 103 (Th to Lw). F-block elements, as well as inner transition elements, are the names given to these elements.

Periodic categorization of elements is a way of grouping elements based on their characteristics, such as keeping elements that are similar in one group and the rest of the elements in the other. Some empty spots have been left in the periodic table to accommodate elements that will be discovered in the future without disrupting the elements’ trending periodicity.

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Classification of Elements 

The classification of elements is the grouping of elements with comparable qualities. Even though each element is unique, there are some commonalities between them. Scientists were finally successful in categorising the various elements into groups or chemical families based on these similarities, allowing comparable elements to be grouped together and dissimilar elements to be separated after showing a group. The periodic table is formed as a result of the classification of elements. The s, p, d, and f-blocks divide the long version of the periodic table into four sections.



  • Elements of the s-block

The last electron in the valence s-sub-shell of the outermost energy shell is filled in the elements in the s-block of the periodic table. This block has just two groups since the s-subshell can only have two electrons (1, 2). Alkali metals are elements that belong to group 1 and have an ns1 electrical configuration. Similarly, alkaline earth metals having an ns2 electrical structure are found in group 2. As a result, s-block elements are group 1 and 2 elements, such as hydrogen and helium, in which the s-orbitals are gradually filled in.

The general electronic configuration of s-block elements is ns1-2 (where n = 2 – 7).

  • Elements of the p-block

The last electron in a P-block element enters one of the three p-orbitals of the corresponding outermost shell. There are six groups in this block because the p-subshell can only hold six electrons (13 to 18). Representative elements are the elements in the periodic table that belong to the s and p-block.

General electronic configuration of p-block elements is ns2  np1-6 (where n = 2 – 7).

  • Elements of the d-block

Elements in which the last electron enters any one of the five d-orbitals of their respective penultimate shells are called d-block elements. The d-block is organised into 10 vertical columns or groups numbered 3 to 12 since the d-subshell can only have five orbitals and ten electrons. Because their ground state has incompletely filled d-orbitals, the d-block elements are known as transition elements.

General electronic configuration of p-block elements is (n–1)d1 – 10ns0–2 (where n = 4 – 7).

  • Elements of the f-block

D-block elements are those in which the final electron enters one of the seven f-orbitals of their respective ante-penultimate shells. All of the f-block elements are divided into two series, each with fourteen elements: in the first series, electrons are filled in the 4f-subshell, which is known as the lanthanoid series (atomic number 5871); in the second series, electrons are filled in the 4f-subshell, which is known as the lanthanoid series. The filling takes place in the 5f-subshell in the second series, which is known as the actinide series.

General electronic configuration of p- block elements is (n-2)f0 – 14(n-1)d0 – 2ns2 (where n = 6 – 7).



Newland’s Law of Octaves

In 1864, a British chemist named John Newlands sought to combine the 62 elements known at the time. He arranged them in ascending order based on their atomic weights and discovered that every eighth element had the same properties. As a result of this discovery, Newland’s law of octaves was born. The law of octaves asserts that when the elements are arranged in ascending order of their atomic masses, every eighth element has similar properties. The elements having equivalent properties according to Newland’s law of octaves are depicted below.

The components’ proximity to musical octaves, in which every eighth note is comparable to the first, was contrasted by Newlands. This was the first time each element was given an atomic number. However, in the scientific community, this method of classifying elements was met with scepticism. While the properties of the eighth element are similar to those of the first, they are ordered in increasing order of their atomic masses.

Some Examples of Newland’s Law of Octaves are,

  • Sodium is one of lithium’s eight elements. Similarly, the chemical characteristics of eight sodium elements are potassium, lithium, sodium, and potassium.
  • Chlorine is the eighth element after fluorine. Fluorine and chlorine have chemical characteristics that are similar.

When elements are organised by increasing atomic mass, Newland’s law of octaves states that the properties of every eighth element are the same as the first.

Limitations of Newland’s Law of Octaves

Newland’s law of octaves has the following main faults.

  • Some elements were placed together in Newland’s periodic classification. For example, cobalt and nickel were placed in the same slot.
  • Distinctive element qualities were grouped together. Metals like cobalt, nickel, and platinum, for example, were classed alongside halogens.
  • Newland’s law of octaves was only valid up to calcium. The atomic masses of elements with higher atomic masses were too large to fit within octaves.
  • The octave layout could not accommodate later found components. As a result, there was no way for new elements to be discovered using this classification scheme.
  • Newland could only organise elements up to calcium out of the entire 56 known elements.
  • After calcium, every eighth element lacked qualities similar to the first.
  • Newlands rearranged the current element order by putting two elements in the same position that have different chemical and physical properties.
  • Iron, for example, has characteristics that are similar to those of cobalt and nickel. Iron, on the other hand, is located far from these elements.

Advantages of  Newland Law of Octaves

  • Some of the advantages of Newlands’ Octaves law are as follows:
  • This law creates a framework for grouping objects with similar characteristics.
  • The Act provided the government with broad powers to compile all known data into a tabular format.
  • The law of octave, developed by Newlands, was the first to rationally based on atomic weight, relating the properties of elements to their atomic masses.
  • This approach performed considerably better for the lighter sections. For example, lithium, sodium, and potassium were combined. Every eighth element has the same qualities as the first. The elements are arranged in order of increasing atomic mass.

Sample Questions 

Question 1: What are the four different types of elements?

Answer:

The four sorts of elements are s, p, d, and f block elements.

Question 2: What are the benefits of element classification?

Answer:



It allows scientists to predict the properties of elements and compounds based on their periodic table positions, and vice versa. The relative properties of elements and their compounds from diverse classes become easier to study, interpret, compare, and contrast.

Question 3: What is Newland’s octave law? Give an example to illustrate your point.

Answer:

When elements are placed in sequence of increasing atomic masses, the properties of the eighth element (beginning from a particular element) are a repetition of the qualities of the first element, according to Newland’s law of octaves.

For example, if we start with lithium as the first element, the eighth element is sodium, which has qualities comparable to lithium.

Question 4: What are the limitations of Newlands’ Octaves Law?

Answer:

The following were the main disadvantages:

  1. Only elements with atomic weights of up to 40 u, or up to calcium, were included. The first and eighth elements did not have the same properties as calcium.
  2. Only 63 elements were assumed to exist in nature, with no new elements predicted to be discovered in the near future. However, the table later encountered a number of new components whose properties did not conform to the octave law.
  3. Some portions that are similar have been split, while others that are not comparable have been placed together in the same column.
  4. The properties of the eighth element were no longer identical to those of the first when noble gases were discovered.It was now the first and ninth element that shared attributes with another.It was now the first and ninth element that shared attributes with another.

Question 5: Why do all of the elements of a group have the same valency?

Answer:

The valency of an element is proportional to the valence of its atom’s electronic configuration. Because all of the elements in a group have the same electrical valence shell configuration. They have a similar valency.




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