As you pass the border (steps) on the periodic table, the atoms tend to form negative ions. Why is this so?

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This is because they want to gain more electrons to become stable. Nonmetals tend to gain electrons more than lose them. Moreover, Ions form in such a way so that the  ion will have the same number of electrons as a noble gas. Take oxygen, for example.  Oxygen has 8 electrons. To become like a noble gas it could either gain two to become  like neon or it could lose six to become like helium. So what will oxygen do—gain two or lose six? As a general rule, atoms will gain or lose the fewest number of electrons  possible.

Explanation:

when atmosphere interacts with biosphere they focuses on on the sources and sinks of green house gases (ghgs) air pollutants, particular matters, water and energy between the earth's surface and the atmosphere. the biosphere affects the climate. the atmosphere and biosphere are in constant interaction with each other, and all living things rely on gases in the atmosphere for life. organisms such as animals take in oxygen gas form the atmosphere to use in every cell of their body for smooth functioning of daily routine exercises.

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.