Periodic table and Classification of Elements

Alfred Ajibola - Tue, 26th March, 2019 @ 18:15: PM

What is the Periodic Table?

The periodic Table (also called periodic table of elements or Mendeleev's table) is the table that shows an organized arrangement of the 118 chemical elements according to their atomic number. (Atomic number is the number of protons in the nucleus of an atom). Out of the 118 elements, elements 1 - 94 are present in nature while elements 95 - 118 are synthesized artificially. Also, the manner at which elements are arranged on this table reveals some similarities in their electronic configuration and chemical properties.  On this table, The Atomic symbol of elements is used to represent each element, for instance Sodium is represented as Na. The atomic number of each element of the periodic table can be seen on the top left (or on top) of each atomol symbol. Also seen are the elements' atomic mass, just below the atomic symbol. (Atomic mass is the sum of protons and neutrons in the nucleus of an atom).

Image Credit: Gstatic


The elements on the periodic table can be classified into the followings:



The vertical columns of the periodic table are called the Groups (up - down). These groups are 8 in numbers (numbered I, II, III, IV, V, VI, VII and VIII). They appear to be the most significant criteria in the classification of elements in the periodic table. Most of the elements within a group have similar chemical properties and share a common name. For instance, the group VIII elements are referred to as the noble or rare or inert gases while groups I, II and VII are called alkali metals, alkali earth metals and halogens respectively. All elements in the same group have the same valence electron(s), for instance all group "I" elements have one valence electron while group "II" elements have got two. (Valence electron is the number of electron(s) in the outermost shell of an atom). These outermost electrons determine the chemical behaviour of elements, giving rise to the basis of the periodic law which states that the properties of the elements are a periodic functions of their atomic numbers. To simply put, elements with the same valence electron(s) will tend to chemically behave in a similar way.



The horizontal rows of the periodic table make up the periods (left - right). They also show some similar trends, for instance, all elements in period one have one shell while elements in period two have got two shells or atomic orbitals (electrons revolve round the shell). Also, as we go across the period, the number of electrons increases by "1".



Elements in the periodic table are also classified into blocks depending on the electrons present on the outermost shell of the elements. For this reason, we have the s-block elements, p-block elements, d-block elements and the f-block elements. Understanding how these configurations are written is important.

Apart for the above classifications, elements in the periodic table can further be classified as transition metals, lanthanides and actinides.

Note: As a student, understanding the chemical properties and trends that elements share within a group or period is vital. These will include atomic radiusionic radius, ionization energy, electronegativity, electron affinity and so on. An article will be written to explain those terms, including the periodic law.

Topics in Chemistry

Physical and Chemical properties of Acids Matter, Mass and Weight Interesting facts about Gold Differences between Molecular Mass and Molar Mass Introduction to Organic Chemistry Emperical Formula explained with worked example Periodic table and Classification of Elements Daltons Atomic Theory and its Modifications Physical Properties of Metals Grahams law of diffusion


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