Write the modern stage formula.
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Answer:
The modern periodic table is developed after the periodic law and a periodic table given by Mendeleev. In the latter part of the 18th century, Mendeleev made his periodic table. Scientists did not know about the internal structure of the atom back then.
The development of various atomic models and advances in quantum theory revealed that the atomic number is the most basic property of a chemical element. This led to the modification of Mendeleev’s periodic law, which is today called as modern periodic law.
The atomic number is equal to the number of electrons or protons in a neutral atom. After knowing the fundamental unit of elements, scientists now had a clear idea about quantum numbers and electronic configuration of elements in the periodic table. After knowing the periodic law, chemists noticed that there is an analogy between the 94 naturally occurring chemical elements. This analogy made people more curious about the chemistry of these elements. Scientists made various artificial elements. A new periodic table was developed based on the modern periodic law by modifying the Mendeleev’s periodic table.
he present form of a periodic table that is widely used across the globe is the long form of the periodic table. In this form of a periodic table, the horizontal rows are called periods and the vertical columns are known as the groups.
Groups consist of elements that have similar outer shell electronic configuration in their atoms. Previously the groups were named as IA,…VIIIA, VIII, IB…VIIB and 0. But now they are named as 1, 2, 3…18. In the modern periodic table, periods are the seven horizontal rows. Principle quantum number ‘n’ decides the period of the element. Principle quantum number (n) is one of the four quantum numbers (n, l, m, and s). It tells us about the principle electron shell. For example, if n= 3, then it indicates the principle shell as 3.