How do I know which part of a compund is negectivly charged and which side is positivly charged? In BH3 how would I know if the B is positivly charged or negetively charged? and for hydrogen?
H is 2.1. B is 2.0. Almost the same. I would write a delta delta (two small delta) + for B and a delta delta - for H. The delta delta + or - signifies an extremely small negative or positive charge. You can carry this when explaining to delta delta delta - and +.
Scroll down to the delta. Both the cap and the lower case are shown.
http://www.mathacademy.com/pr/prime/articles/greek/index.asp
For something that has 3 different elements how would I know which is positive and which is negetive? For exmaple HCN.
HCN is a linear moecule, H-CtriplebondN so you write H as the + end and CN as the negative end. If you are forced into breaking it down further, just use the electronegativities. H is 2.1, C is 2.4, and N is 3.0, so I would write H as +, N as negative, and C as delta delta +. When you get into the three dimensional arrangement of HCN and other polyatomic molecules, you will see how it is done spatially.
Why isnt the carbon negetive ?
But most polyatomic ions, as CN, SO4^=, CLO4^- etc are considered together not separately.
Ohhhh OK. Thank you :)
C is 2.4 and N is 3.0; therefore, N must be negative with respect to C. Then the H is 2.1 and it must be positive with respect to C. You see why trying to assign partial + or - charges to everything becomes problematic.
Ohh. Yes I do see that. Thanks :)
To determine the charges within a compound like BH3, you need to consider the electronegativity of the elements involved. Electronegativity is a measure of an atom's ability to attract electrons towards itself in a chemical bond. Elements with higher electronegativity tend to attract electrons more strongly, resulting in a partial negative charge (δ-) on that atom, while the atom with lower electronegativity would have a partial positive charge (δ+).
In the case of BH3, boron (B) has a lower electronegativity compared to hydrogen (H). As a result, the hydrogen atoms tend to pull the shared electrons of the B-H bonds closer to themselves, resulting in a partial positive charge on the hydrogen atoms (δ+). Conversely, boron carries a partial negative charge (δ-) due to the electron-withdrawing effect of the hydrogen atoms.
To recap:
- Boron (B) in BH3 is partially negatively charged (δ-).
- Hydrogen (H) atoms in BH3 are partially positively charged (δ+).
It's important to note that the charges in BH3 are not full charges like +1 or -1 but rather partial charges due to electron distribution. Electronegativity trends in the periodic table can be useful for estimating charge distribution, but more accurate values can be found in electronegativity tables or through experimental data.