How many electrons must the atoms of the elements below share with other atoms in covalent bonding to achieve an octet of electrons

air quality

poor drinking water

and heavy polution

can lead to poor health

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.

the answer is 0.42 is that is an option. this question provides no info