Explain the outline of the modern periodic table.

1.	Explain the outline of the modern periodic table.
Answer» SOLUTION :In the modern periodic table, the elements are ARRANGED in the increasing order of atomic NUMBERS. The atomic number of any element is equal to the number of protons in the nucleus. The number of protons in the nucleus is equal to the total number of electrons in the atom. In the modern periodic table, elements having same number of valence electrons are placed in vertical columns called groups. The vertical columns of elements in a periodic table are called groups. The horizontal rows of elements in a periodic table are called periods. The modern periodic table consists of 18 groups and 7 periods. Electronic configuration of elements in a period : Period number indicate the value of .n or shell (orbit) number .n. is the number of the given shell starting from the nucleus. The maximum number of electrons that can be accommodated in any shell is `2n^(2)`, where .n. is the number of the given shell. Electronic configuration of elements in a group : All the elements in any group of the periodic table have IDENTICAL outershell electronic configuration. All the elements in a group have same number of electrons in their valence shell as well as they have similar properties. The valence shell electronic configuration of ALKALI metals is ns which is shown below:

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