Answer:
Three hydrogen atoms to form PH₃.
Explanation:
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In this case, since the elements belonging to the nitrogen family (N, P, As, Sb and Bi) show five valence electrons, because there are five electrons at their outer shell, it is clear that if phosphorous bonds with hydrogen, it is going to require the same amount of oxygen atoms (3) because elements having five valence electrons need 3 bonds in order to attain the octet (5+3=8).
Therefore the compound would be:

Which is phosphine.
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Answer:
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Answer:
The statement true is A. A and B are isotopes of the same element.
Explanation:
Isotopes correspond to atoms of the same element with different mass numbers (A), that is to say they differ in the amount of neutrons in the nucleus. In the case of compound A it has 10 neutrons, and B has 11.
this is a dilution question where a certain volume is taken from a more concentrated solution and diluted to make a solution with a lower concentration.
the dilution forumla is as follows
c1v1 = c2v2
where c1 is concentration and v1 is volume of the more concetrated solution
c2 is concentration and v2 is volume of the diluted solution
substituting the values in the equation
18.0 M x V = 0.126 M x 16.5 L
V = 0.1155 L
volume of 115.5 mL is taken from the 18.0 M solution and diluted upto 16.5 L solution.