1) How are elements classified? Explain with examples.
Dear student, Initially all the elements were only classified into two groups namely metals and non metals. The main disadvantage was that the metals group was quite big and certain elements had the properties of both metals and non metals. Hence there was a need for a more lucid classification.
Russian chemist Dmitry Mendeleev arranged the elements based on their chemical and physical properties in a tabular form known as the ‘periodic table’. It is ‘periodic’ in the sense that after a certain interval, the physical and chemical properties repeat themselves.
The periodic table arranges all of the known elements in order of increasing atomic number. Order generally coincides with increasing atomic mass. The different rows of elements are called periods. The period number of an element signifies the highest energy level an electron in that element occupies (in the unexcited state). The number of electrons in a period increases as one moves down the periodic table; therefore, as the energy level of the atom increases, the number of energy sub-levels per energy level increases.
Elements that lie in the same column on the periodic table (called a "group") have identical valance electron configurations and consequently behave in a similar fashion chemically. For instance, all the group 18 elements are inert, or noble gases.
Element groups are either nonmetals or various subsets of metals, but there is no distinct line between the two types of elements. Metal elements are usually good conductors of both electricity and heat. Subsets are based on similar characteristics and chemical properties.
Regards
Initially all the elements were only classified into two groups namely metals and non metals. The main disadvantage was that the metals group was quite big and certain elements had the properties of both metals and non metals. Hence there was a need for a more lucid classification.
Russian chemist Dmitry Mendeleev arranged the elements based on their chemical and physical properties in a tabular form known as the ‘periodic table’. It is ‘periodic’ in the sense that after a certain interval, the physical and chemical properties repeat themselves.
The periodic table arranges all of the known elements in order of increasing atomic number. Order generally coincides with increasing atomic mass. The different rows of elements are called periods. The period number of an element signifies the highest energy level an electron in that element occupies (in the unexcited state). The number of electrons in a period increases as one moves down the periodic table; therefore, as the energy level of the atom increases, the number of energy sub-levels per energy level increases.
Elements that lie in the same column on the periodic table (called a "group") have identical valance electron configurations and consequently behave in a similar fashion chemically. For instance, all the group 18 elements are inert, or noble gases.
Element groups are either nonmetals or various subsets of metals, but there is no distinct line between the two types of elements. Metal elements are usually good conductors of both electricity and heat. Subsets are based on similar characteristics and chemical properties.
Regards
