Electronegativity (χ) is a bit like the popularity contest of atoms. It's a measure of how much an atom wants to hang out with electrons, particularly when it's in a covalent bond (think of it like sharing a dessert with a friend - some friends hog the dessert, just like some atoms hog the electrons!).

Just like there's a pecking order in a school playground, there's a similar order in the world of atoms. On the periodic table, electronegativity increases as you go across periods (left to right) and up groups (bottom to top). This makes fluorine the 'cool kid' of the periodic table - the most electronegative element, always drawing the electrons towards itself.