Final answer:
Electronegativity is a relative measure of an atom's ability to attract electrons in a covalent bond and generally increases across a period and decreases down a group on the periodic table.
Step-by-step explanation:
The correct answer to the provided question about electron gravity is 'A: is a relative measure of an atom's attraction for electrons it shares in a covalent bond.' This concept is actually known as electronegativity, which is defined as the ability of an atom to attract shared electrons when the atom is part of a covalent bond. Electronegativity values on the periodic table typically increase from left to right across a period, and electronegativity plays a crucial role in determining the polarity of covalent bonds and the physical and chemical properties of molecules.
It's important to note that electronegativity is not the same for all elements in a family or group; instead, it generally decreases as you move down a group due to the increasing atomic radius, which places the valence electrons further from the nucleus and weakens the electrostatic pull. Moreover, electronegativity should not be confused with electron affinity, which is the energy change that occurs when an atom gains an electron.