How does an ionic bond form?

Why does Aluminum chloride form a covalent bond instead of an ionic ?

• 2 Questions: 1) Why does Aluminium Chloride form covalent bonds instead of ionic ? 2) Why does Aluminium Fluoride form ionic bonds instead of covalent ?

• Answer:

  Dear Shaun W, AlCl3 - Molecular compound ( molecular formula) - Type III - Binary covalent compound - Apparent charges Al (+3) and Cl (-1) - EN (electronegativity) Al is 1.61 - EN (electronegativity) Cl is 3.16 - the difference in electronegativity is 1.55 AlF3 - Ionic compound ( formula compound) - Type I - Binary ionic compound - Ionic charges Al (+3) and F (-1) - EN (electronegativity) Al is 1.61 - EN (electronegativity) F is 3.98 - the difference in electronegativity is 2.37 The fluorine atom (F) is the most electronegative of all the elements, and the francium atom (Fr) is the least electronegative of all the elements. "Electronegativity (EN), is the chemical property that describes the ability of an atom (or, more rarely, a functional group), to attract electrons(or electron density) towards itself in a covalent bond (or ionic bond)." Trends in Electronegativity (Periodic Trends): "In general, the electronegativity of the atoms (elements) on the periodic table of elements increases on the passing from left to right along the period, and decreases from top to the bottom on desending on a group." Example #1: Sodium (Na) and Chlorine (Cl) = Ionic Bond ______________________________________… *There is a very large difference in electronegativity, so * the chlorine aton takes on the electron from the sodium atom, * converting the atom's into ions Na(+1) and Cl(-1). * These are held together by their opposit electrical charges forming ionic bonds. * Each sodium ion is held by 6 chlorine ions while each chlorine is held by 6 sodium ions. Example #2 : Carbon (C) and Oxygen (O) = Covalent Bond ______________________________________… *There is only a small difference in electronegativity, so *the two atoms share the electrons, *the result of this sharing a pair of electrons forms a covalent bond between the atoms of the elements. *that is the atoms a held together by mutual affinity for their shared electrons. (and depicted by C:O or C--O) *an array of atoms that are held together by covalent bonds forms a true molecular compound. Example #3: Hydrogen (H) and Oxygen (O) = Polar Covalent Bond ______________________________________… *There is a moderate difference in the eletronegativity, so * the oxygen atom pulls or tugs on the electron of the hydrogen atom closer to itself. *Result: a polar covalent bond is formed. *Oxygen does this with 2 hydrogen atoms to form a molecule of water H2O. It is my sincere hope and prayer that the information provided will be able to assist you in your information quest. " May the Lord Jesus Christ continue to bless you and keep you always in His Love and Grace.........." Sincerely yours, [email protected] (a.k.a. calvaliear)