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Elements are the fundamental building blocks of all matter in our environment. Only 31 chemical elements have been found before 1800. In 1865, a total of 63 new elements were discovered. The periodic classification of elements became necessary as a result. There are 118 elements that we are currently aware of. Some of the 118 chemical elements are the result of human activity.
Classification of the Elements in the Periodic Table:
Based on their electrical configurations, the elements in the periodic table can be categorised in four ways:
Noble gas Elements – Noble gas elements are elements in group 18 of the modern periodic table. The initial element in this group (helium) has an electrical configuration of 1s2. The remaining elements (neon, argon, krypton, xenon, and radon) share an electrical configuration of ns2 np6. These elements are particularly stable since their octet is full.
Representative elements – S-block and p-block elements are two instances of representative elements. S – block elements refer to the items in groups 1 and 2. (elements with 1s2 and 2s2 outermost configuration). The p-block components are those in groups 13-17. (outermost configuration varies from ns2 np1 to ns2 np5).
Transition elements –Transition elements are elements that belong to groups 3 to 12 and have an electrical configuration of (n-1)d1-10 ns1-2 on their outer shell. D-block elements are another name for these elements.
Inner transition Elements – Elements of inner transition: The lanthanides and actinides series, which are situated at the bottom of the periodic table, are the inner transition elements. These elements have partially filled 4f and 5f orbitals, giving them distinctive features.
Advantages of classifying elements in the Periodic Table
Today, we know about 116 elements.
During the 18th and 19th centuries, most of the elements we know today were discovered.
Many scientists had given their time and effort to carefully arrange the elements in a table. As a result, the Periodic Table that we use today was created.
The Periodic Table’s systematic classification of elements gives the following benefits.
- Chemists can use it to analyse and comprehend the properties of elements and their compounds in a more systematic and organised manner.
- It allows scientists to predict the properties of elements and their compounds based on their placements in the Periodic Table, as well as the other way around.
- It is simpler to study, analyse, compare, and contrast the associated properties of elements and their compounds from various groups.
Earlier attempts in classifying elements
1.Classification of Greeks
The ancient Greeks incorrectly assumed that all matter was made up of only four elements: earth, air, fire, and water. However, the experiments did not confirm their hypothesis.
The contribution of Dalton
The following are some of Dalton’s most noteworthy contributions.
Simple bodies (elements) and compound bodies make up all matter (compounds). The atom is the smallest component of an element . The compound atom is the smallest component of a complex body (later called the molecule).
(ii) The properties of all atoms in the same element are the same, such as form, size, and mass. Distinct elements have different properties in their atoms.
(iii)When matter undergoes chemical transformations, atoms of various elements either mix or separate.
(iv)Atoms can’t be destroyed, even if the environment changes.
In his ‘Table of the relative atomic weights of the ultimate particles of gaseous and other things,’ published in 1808, John Dalton produced the first list of atomic weights.
He shifted chemists’ thinking from qualitative to quantitative, kicking off the 19th-century chemical revolution.
Prout’s Hypothesis
Prout proposed in 1814 that hydrogen is the source of all other elements. To put it another way, Prout suggested that hydrogen is the most basic element. Prout came to this conclusion after noticing that atom masses are whole number multiples of hydrogen’s atomic mass. This theory gave rise to the concept of atomic mass, which is defined as the relative mass of an atom on a scale where hydrogen has a mass of one unit. Later, oxygen was adopted as the industry standard. Later, the notion of the atomic mass unit (amu) was established, using carbon-12 as a benchmark.
Prout’s concept sounded groundbreaking at the time. Prout may have been close to the truth, it now appears.Modern scientists believe that all elements can be derived from hydrogen based on evidence from studies of radioactive alterations.
Classification based on the value of the item
Recognizing the relevance of valency in chemistry, an attempt was made to categorise elements based on it.
The monovalent elements, as well as the divalent, trivalent, and other elements, were grouped together.
However, there are a number of disadvantages to this categorisation.
(I) The valency of certain elements varies, for example, iron has a valency of 2 and 3, copper has a valency of 1 and 2, tin has a valency of 2 and 4, lead has a valency of 2 and 4, and so on. As a result, the placement of such elements is unknown.
(ii) Such classification does not explain the diverse nature of elements having the same valency. For example, both sodium and chlorine are monovalent, but they are quite different from each other in chemical behaviour. Sodium is a strongly electropositive metal whereas chlorine is a strongly electronegative nonmetal.
Lavoisier’s classification
More than 60 chemical elements had been recognised by the late 1860s. Lavoisier and early chemists divided the elements into metals and non-metals based on similar physical and chemical properties.
I Metals are elements that are malleable and ductile, good conductors of heat and electricity, and have a distinctive metallic sheen.
(ii) Non-metals were defined as brittle materials that were poor conductors of heat and electricity and lacked a metallic sheen.
Antimony, arsenic, boron, silicon, and tellurium, for example, were metalloids because they resembled metals in some ways and non-metals in others.
Conclusion
The grouping of elements creates a fixed pattern in which the properties of the elements change on a regular basis. The periodic table simplified and arranged the study of physical and chemical properties of elements.To understand it simply and effectively.Elements are arranged on it in order of increasing atomic number. The position of an element on the table, on the other hand, conveys a lot more about it than the number of protons in its nucleus. The periodic table, as we have seen, includes a wealth of information on an element’s chemical and physical properties.
