Final answer:
Electronegativity measures an atom's ability to attract electrons in a compound and generally increases across a period on the periodic table. It decreases within a group as you move down due to an increase in atomic radius.
Step-by-step explanation:
Electronegativity is a measure of the ability of an atom to attract electrons when the atom is part of a compound. This chemical property reflects how strongly an atom can pull electron density towards itself when forming a covalent bond. Typically, electronegativity values increase from left to right across a period on the periodic table.
Within a group or family on the periodic table, the electronegativity generally decreases as you move down. This is because atoms lower in a group have more filled electron shells, thus increasing their atomic radius and weakening their attraction for additional electrons. Contrary to one of the options given, electronegativity is not the total negative charge on a polyatomic ion, nor is it the same for all elements in a family or group.
It's important to note that the most electronegative element is fluorine, which has an electronegativity value of 3.98, serving as a reference point for other elements. When atoms with different electronegativities form covalent bonds, the difference in electronegativity determines the polarity of the bond, with electrons being more attracted to the atom with higher electronegativity.