Question

The oxidising power of elements increases on moving from left to right along a period in the periodic table. give reason

Answer 1

The electropositivity (the power to give away electrons) increases as we move right to left in the periodic table.This results in a higher valence since electropositivity affects the valence or here,the oxidation number.
Hence the oxidation number/oxidizing power increases as we move from left to right in the modern periodic table.
Hope this helps :)

Answer 2

Oxidising power is the tendency of an element to accept electron.The greater is its ability greater will be its oxidising power

Down the group the effective nuclear charge decreases whereas across the period the oxidising power increases as the effective nuclear charge increases across the perid

The periodic table tendency for effective nuclear charge:

Increase across a period (due to increasing nuclear charge with no accompanying increase in shielding effect).

Decrease down a group (although nuclear charge increases down a group, shielding effect more than counters its effect)