The answer is ClF3. This molecule is a good illustration of VSEPR (valence shell electron pair repulsion) theory with Cl as the central atom with 7 valence electrons and each F atom contributing 1 electron. This forms an "expanded octet" of 10 electrons (5 electron pairs).
The octet rule states that the element will try to attain 8 electrons in its outer-most shell. Following this, chlorine should share only electron but is sharing 3.
