Since you did not give the reactions, i cannot give the answers.
In organic and inorganic chemistry, nucleophilic substitution is a fundamental class of reactions in which an electron rich nucleophile selectively bonds with or attacks the positive or partially positive (+ve)charge of an atom or a group of atoms to replace a leaving group; the positive or partially positive atom is referred to as an electrophile. The whole molecular entity of which the electrophile and the leaving group are part is usually called the substrate.
The most general form for the reaction may be given as the following:
<span>Nuc: + R-LG → R-Nuc + LG<span>:</span></span>
Nitrogen is the chemical element with the symbol N and atomic number 7. ... At standard temperature and pressure, a colourless and odorless atomic gas with the formula N. nitrogen forms about 78% of Earth's atmosphere.
Radioisotopes are used to study chemical reactions because of the fact that they attach radioactive isotopes to certain atoms.<span> Tracer radioisotopes used to study chemical reactions in molecular structures by adding radioistopes to reactants and using the uptake compared to the original isotope. </span>
Covalent bond forms between the oxygen and hydrogen atoms.
(I attached a picture that could help)
-Hope that helps,
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