''The physical and chemical properties of the elements are periodic functions of their atomic numbers'' is known as Modern periodic law.There are 18 groups and 7 periods in the modern periodic table.It was proposed by Moseley. You can see the modern periodic table in the below image.
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The Modern Periodic Law is stated as: "Properties of elements are a periodic functions of their atomic number". Atomic number is the basis for modern periodic table.
Atomic number is the number of protons in the nucleus, it is also equal to the number of electrons in the atom.•  Elements are arranged in the increasing order of atomic numbers.
        •  Horizontal rows in the periodic table are called periods and vertical columns in the table are called groups.
        •  Elements in the modern periodic table are arranged in 7 periods and 18 groups.
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