Question

how many period and group does modern periodic table has​

Answer 1

Answer:

seven periods

There are seven periods in the periodic table, with each one beginning at the far left. A new period begins when a new principal energy level begins filling with electrons. Period 1 has only two elements (hydrogen and helium), while periods 2 and 3 have 8 elements. Periods 4 and 5 have 18 elements.

Answer 2

Answer:

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There are 18 groups in the periodic table.

These groups are numbered from 1 to 18.

And

There are 7 periods in the periodic table.

These are numbered as 1, 2, 3, 4, 5, 6 and 7 from top to bottom.

• Groups - There are 18 vertical columns in the periodic table. Each column is called a group. All elements in a group have similar chemical and physical properties because they have the same number of outer electrons.

• Periods - In periodic table elements are arranged in a series of rows. Elements of the same period have the same number of electron shells.