Question

Explain, the statement 'In each period, the atomic radii gradually decrease with increase in atomic number'. Give one example to justify your answer.

Answer 1

Atomic radius of elements depends on number of shells and nuclear charge on the atom. The number of shells in a period is same for all atoms; hence, the only factor that governs the variation in atomic radii across a period is nuclear charge. Increase in nuclear charge will decrease the atomic radii because increase in positive charge of nucleus attracts the outermost electrons more strongly towards itself. Nuclear charge increases from left to right across a period with addition of electron; hence, atomic radii decreases accordingly. For example, carbon atom (atomic number 6) with a nuclear charge value of +6 has an atomic radii of 0.77Å and oxygen atom (atomic number 8) with a nuclear charge of +8 has an atomic radii of 0.74Å.