Which one of the following statements best describes electronegativity in atoms? A) Electronegativity is what happens when an atom gains an electron to become an anion.
B) Electronegativity is the attraction an element's nucleus has for the electrons in a chemical bond
C) Electronegativity is the energy lost when an atom gains an electron
D) Electronegativity is the energy absorbed when an atom loses an electron

B) Electronegativity is the attraction an element's nucleus has for the electrons in a chemical bond

Explanation:

Electronegativity is defined as the property of an element to attract a shared pair of electron towards itself.

When the size of an atom decreases as we move across the period, as the electrons get added to the same shell and the nuclear charge keeps on increasing. Thus the electrons get more tightly held by the nucleus.

As, the size of an element decreases, the valence electrons come near to the nucleus. So, the attraction between the nucleus and the shared pair of electrons increases and thus the electronegativity increases.

answer:

technetium is the most reactive. this is followed by silver. the least reactive out of these three elements is strontium.