How does the absorption of ultraviolet radiation by the ozone layer sustain life? a. this process maintain the temperature of the earth. b. it keeps a low level of harmful ultraviolet radiation from reaching living organisms. c. this process keeps ozone concentrations in the troposphere at lower levels. d. all of the above are true.

d. All of the above are true.

Explanation: Ozone is a protective shield present in earth's stratosphere which absorbs the harmful radiations from the sun and thus keeps a low level of harmful ultraviolet radiation from reaching living organisms.

As the sun rays are absorbed by the ozone layer, not all the sun rays reach the earth's surface and thus the temperature of the earth is also maintained.

The ozone present in the troposphere also called as ground level ozone is harmful as it can trigger a variety of health problems and is formed by reactions of pollutants from vehicular emissions in the presence of sunlight. Thus ozone in stratosphere blocks the sunlight and thus prevents the formation of ground level ozone.

Thus all the statements are true.

explanation:

metals have excess of electrons whereas non-metals have deficiency of electrons. thus, in order to gain stability metals easily donate their electrons to the non-metals.

for example, electronic configuration of sodium is and electronic configuration of phosphorous is .

when a phosphorous atom and sodium atom combine together then sodium will donate is extra one electron to the phosphorous atom. as a result there will be formation of ionic bond between sodium and phosphorous.

the reaction will be as follows.

there, are three sodium sodium atoms and each of them will donate its one extra electron to phosphorous atom. thus, the sub-shell of phosphorous gets completely filled.  

thus, we can conclude that electrons are transferred from atoms of sodium to atoms of phosphorous. this transfer makes the sodium atoms donate one electron and the phosphorous atoms to gain one electron. as a result, the sodium and phosphorus atoms strongly attract each other.