Question

define activity series of metals arrange the metal gold copper iron and manganese in the order of their increasing reactivity

Answer 1

it is a Series in which metal are arranging according to decreasing Reactivity power.
*gold
*copper
*iron
*manganese
Hope it helps u☺

Answer 2

The activity series is a list of metals arranged in the order of their decreasing activities.
......
Increasing reactivity...
Gold
Copper
Iron