Is MgCl2 polar or non polar? Does it have ion-dipole forces? How can I discern between polar and non polar molecules?

4 Answers

• I’ll explain at as simple as I can. MgCl2 is a polar molecule. If you draw out it lewis structure, you will notice how the lone pairs on top of Magnesium causes for the entire molecule to have a bent molecular geometry. Because the molecular geometry is bent, it’s not symmetrical thus leading MgCl2 being polar since the dipole forces are pulling downwards. MgCl2 is polar-ionic.

  This compound does have an ion-dipole force. An easy way to determine that is you have to first look and see if the compound is ionic or an cation plus an anion. After that’s confirmed, take a look at the charges of both of the atoms. If the numbers are different, i.e.: +2 and -1, then it is an ion-dipole intermolecular bond. If the compound is ionic and the numbers are the same, i.e.: +1 and -1 then it is an ion-ion intermolecular bond. In this case, the charge of Mg is +2 and the charge of Cl is -1, this makes it an ion-dipole bond (2nd strongest after ion-ion).

  A simple way of distinguishing between polar and non-polar molecules is drawing out the lewis structure. Taking a look at its molecular or electron geometry is a key indicator of determining whether the compound is polar or not. If the molecular geometry is linear, then it’s likely that the compound will be non polar due to the fact that it is symmetrical (3-D). If the electron geometry is a tetrahedral, then it is also likely that the compound will be non-polar due to the symmetry. However, the only way a compound would be polar is if the atoms in the compound have different electronegativities. That is one main reason for a compound being polar. Another reason would be the lone pairs causing the shape of the compound to shift and the dipole forces not canceling out.

  Hope that was clear. If I missed anything, let me know.

• Usually the shape of the molecule will give you the information

  Mg has 2 valence electrons

  Cl has 5 valence

  Mg is the central atom

  It bonds with each Cl because each Cl needs one electron

  That makes the Cl octet happy. And this is symetrical because the Cl will push each other as far as they can which is 180 degrees sp2 hybridized if you know about that

  Now middle has 2 bonds giving it 4 electrons

  It needs 4 more electrons to be octet happy so that means two more electrons share with Mg

  From each Cl

  This means the atom is perfectly symmetrical and so has. No polarity

  Look at h2O if you like to see polarity

  It has 2 unbonded electron pairs on the central O molecule

  And one bonds on each of the H

  Since there is sp3 hybridization because it has 4 bonds

  2 unbonded electron pair

  2 hydrogen bond

  Now the two unbonded electron pairs are more negative then the H bonds

  The electron pairs push together the hydrogen bonds making the angle is smaller than usual

  Creating polar

• Magnesium chloride, MgCl2, is NOT molecular, it is a network solid with alternating Mg and Cl atoms throughout the entire sample. MgCl2 is merely the empirical formula. Therefore, any reference to it being a polar or nonpolar molecule are not applicable.

  Note: Nothing that “Forever” has said about MgCl2 is actually true. It is not a polar molecule. The Lewis structure is fictitious. Lewis structures are only applicable to discrete molecules. It is not a “bent” molecule, the structure of MgCl2 is represented by…. https://upload.wikimedia.org/wikipedia/commons/e/e…

  The remained of what “Forever” describes is also incorrect since magnesium chloride is not molecular.

  If you are going to deal with “polar” vs “nonpolar” molecules, then choose a substances which actually exist as discrete molecules. Water is a common example of a molecular substance which is polar, that is, it has a net dipole moment which is not zero. Because water molecules have two lone pairs and two bonding pairs on the central oxygen atom the molecule is bent and therefore, polar.

  Carbon dioxide, CO2, also exists as discrete molecules. CO2 is nonpolar since it is linear. Therefore are no lone pairs of electrons on the central atom to give a bent molecule.

  To get a grip on molecular geometry and polarity you need to become familiar with VSEPR theory.

  #electron pairs ….. e- pair geom….. molecular geom….. bond angle

  2 …………………….. linear ……………….. linear ……………….. 180

  3 (no lone pairs) .. trigonal planar …… trigonal planar …… 120

  3 (one lone pair) .. trigonal planar …… bent …………………..LT 120

  4 (no lone pairs) .. tetrahedral ………… tetrahedral ………… 109.5

  4 (one lone pair) .. tetrahedral ………… trigonal pyramidal . LT 109.5

  4 (2 lone pairs) …. tetrahedral ………… bent ………………….. LT. 109.5

  5 (no lone pairs) .. trig bipyramidal ……trig bipyramidal …. 90 and 120

  5 (one lone pair) .. trig bipyramidal ….. see-saw ……………. 90 and 120

  5 (2 lone pairs) …. trig bipyramidal ……T-shaped ………..,… 90

  5 (3 lone pairs) …. trig bipyramidal ……linear ………………….180

  6 (no lone pairs) .. octahedral ………… octahedral ………….. 90

  6 (one lone pair) .. octahedral ………… square pyramidal ….90

  6 (2 lone pairs) …. octahedral ………… square planar ……….90

  (LT = “less than”)

• polar. electronegativity difference > 1.7