The electronegativity of an element indicates how strongly the element can attract electrons. Elements that usually have close to a full valence shell of electrons typically have a high electronegativity. Some examples of elements with high electronegativities are oxygen and fluorine.
Electronegativity values have a large impact on bonding. If elements have a low electronegativity strength, they are likely to donate electrons and create ionic bonds. This can be seen in bonding done by most metal elements. If both elements have a high electronegativity, they are likely to share electrons and form covalent bonds. However, the atom with the higher electronegativity may become slightly negative since it pulls the shared electron closer.