Identify the element whose compounds show phosphorescence.

Hint: According to the given question, to know the element whose compounds show phosphorescence, firstly we will explain the concept and the properties of phosphorescence and then we will discuss the element that shows the properties of phosphorescence.

Complete answer:
Phosphorus compounds are phosphorescent. They store light and give it off later.
Phosphorescence is a type of photoluminescence related to fluorescence. When exposed to light (radiation) of a shorter wavelength, a phosphorescent substance will glow, absorbing the light and reemitting it at a longer wavelength. Unlike fluorescence, a phosphorescent material does not immediately reemit the radiation it absorbs.

Instead, a phosphorescent material absorbs some of the radiation energy and re-emits it for a much longer time after the radiation source is removed. In a general or casual sense, there is no unmistakable limit between the discharge seasons of fluorescence and brightness (i.e.: if a substance gleams under a dark light it is by and large thought to be fluorescent, and on the off chance that it sparkles in obscurity it is frequently basically called glowing).

In a cutting edge, logical sense, the wonders can for the most part be arranged by the three distinct instruments that produce the light, and the normal timescales during which those components emanate light. While fluorescent materials quit emanating light inside nanoseconds (billionths of a second) after the excitation radiation is taken out, glowing materials may keep on discharging a phosphorescence going from a couple of microseconds to numerous hours after the excitation is taken out.

Hence, the element Phosphorus whose compounds show the property of phosphorescence.

Note: The reason phosphorescence lasts longer than fluorescence is because the excited electrons jump to a higher energy level than for fluorescence. The electrons have more energy to lose and may spend time at different energy levels between the excited state and the ground state.