Final answer:
Group 1 elements have the lowest electronegativity mainly due to their larger atomic size, which increases electron shielding and reduces the electrostatic attraction between the nucleus and valence electrons.
Step-by-step explanation:
Group 1 elements are known for having the lowest electronegativity on the periodic table. One of the primary reasons for this is their larger atomic size. As you move down Group 1, the atomic radii increase due to the addition of electron shells, which increases the distance between the nucleus and the valence electrons. This increased distance results in less electrostatic attraction between the nucleus and the valence electrons, making the atoms less effective at attracting additional electrons. Moreover, with every added electron shell, there’s more electron shielding, which hinders the nucleus' ability to attract electrons from other atoms. The result is a low electronegativity. Thus, the correct answer would be C) Larger atomic size. Additionally, the fact that Group 1 elements become larger as electrons are added and form anions does show the relationship between size and electronegativity negatively correlates. However, the comparison in ionic sizes between Group 16 and 17, and statements about ionization energies and electron shielding further illustrate how atomic and ionic sizes, effective nuclear charge, and inner electron shielding affect an element's ability to attract electrons.