No, chlorine is not more electronegative than sodium. Electronegativity is a measure of an atom's ability to attract electrons. The more electronegative an atom is, the more strongly it attracts electrons. On the periodic table, electronegativity generally increases from left to right across a period and decreases from top to bottom within a group. Chlorine is located in the same period as sodium but to the right of it. This means that chlorine is more electronegative than sodium.