The periodic table
Period — পর্যায়
Quick answer
A period is a horizontal row of the table; along it, elements slowly shift from metal to nonmetal.
Definition
A period is one of the seven horizontal rows of the periodic table. The period number equals the number of electron shells being filled: period 3 elements like sodium, magnesium and chlorine are all writing electrons into their third shell. Moving left to right, atoms gain protons and the nuclear pull tightens, so metallic character fades, atomic radius shrinks and ionization energy climbs. Period 1 has just two elements; periods 6 and 7 hold 32 each.
For example
Walk period 3 from sodium to argon: a soft reactive metal, magnesium, aluminium, silicon the semiconductor, phosphorus, sulfur, a choking yellow-green gas — then argon closes the row in calm.