How can u predict if a bond will be ionic, covalent or polar covalent?
i know that its the difference between electronegativities, but i cant seem to find the numbers it has to be between for each.
I'm also getting confused because isnt covalent the same as polar covalent?
Last question first.
No, a polar covalent bond is not the same as a covalent bond. A pure covalent bond occurs between two atoms of the same kind; for example, H2, N2, Cl2, F2, etc. But if the bond is between two different atoms what might otherwise be a covalent bond is a polar covalent bond. HCl gas is a polar covalent bond because H has an electronegativity of 2.1 and Cl has EN of 3.0 (check me on that--this is from memory). HF is polar covalent as is HI, HBr, etc. ClF is polar covalent. It is true that all polar covalent bonds are covalent but not all covalent bonds are polar.
Now to the other part of the question. You're right, the difference in electronegativity is the way to know if the bond is covalent, ionic, etc. Where is the dividing line? About 1.9. Some books use 1.7, some have used 2.0 and different teachers use different cut offs. I was taught to use 1.9 as the 50-50 mark; that is, a difference of 1.9 meant the bond was 50% covalent/50% ionic. Few bonds are 100% ionic and few are 100% covalent. GENERALLY, we call the bond ionic if it has more than 50% ionic character and we call it covalent if the bond is more than 50% covalent character. An EN difference of about 1.0 is 25% ionic/75% covalent. Technically those are polar covalent bonds although we may refer to them as covalent. NaF then is ionic with an EN difference of 3.1. I call NaN3 ionic; the EN difference is 2.1 but it may be about 60% ionic/40% covalent or something like that.
I hope this helps clear up the confusion.
To predict whether a bond will be ionic, covalent, or polar covalent, you can consider the difference in electronegativities between the atoms involved in the bond.
Electronegativity is a measure of the tendency of an atom to attract electrons towards itself in a chemical bond. The greater the difference in electronegativities between two atoms, the more likely the bond will be ionic.
Here's how you can use electronegativity differences to predict the type of bond:
1. Ionic bond: If the electronegativity difference between the two atoms is greater than 1.7, the bond is considered ionic. In this type of bond, one atom will strongly attract electrons from the other, resulting in the formation of ions.
2. Covalent bond: If the electronegativity difference between the two atoms is less than 0.5, the bond is considered covalent. In a covalent bond, the electrons are shared equally or near-equally between the atoms.
3. Polar covalent bond: If the electronegativity difference between the two atoms is between 0.5 and 1.7, the bond is considered polar covalent. In a polar covalent bond, one atom attracts the shared electrons more strongly than the other, resulting in a partial positive charge on one atom and a partial negative charge on the other.
It's important to note that while covalent and polar covalent bonds both involve the sharing of electrons, the difference lies in the degree of electronegativity difference between the atoms. Covalent bonds have a smaller electronegativity difference, while polar covalent bonds have a slightly larger difference.
To determine the electronegativity values for specific elements, you can refer to the periodic table. There are multiple scales for electronegativity values, such as the Pauling scale or the Mulliken-Jaffe scale, depending on the source. However, the general trends remain consistent among the scales.
Remember that these rules provide a general guideline, and there are exceptions and variations in certain compounds.