To know this you pretty much do have to kind of memorize a few electronegativities. I don't recall ever getting a table of electronegativities on an exam.
From the structure, you have:
I remember the following electronegativities most because they are fairly patterned:
EN
H
=
2.1
EN
C
=
2.5
EN
N
=
3.0
EN
O
=
3.5
EN
F
=
4.0
EN
Cl
=
3.5
Notice how carbon through fluorine go in increments of
~
0.5
. I believe Pauling made it that way when he determined electronegativities in the '30s.
Δ
EN
C
−
Cl
=
1.0
Δ
EN
C
−
H
=
0.4
Δ
EN
C
−
C
=
0.0
Δ
EN
C
−
O
=
1.0
Δ
EN
O
−
H
=
1.4
So naturally, with the greatest electronegativity difference of
4.0
−
2.5
=
1.5
, the
C
−
F
bond is most polar, i.e. that bond's electron distribution is the most drawn towards the more electronegative compound as compared to the rest.
When the electron distribution is polarized and drawn towards a more electronegative atom, the less electronegative atom has to move inwards because its nucleus was previously favorably attracted to the electrons from the other atom.
That means generally, the greater the electronegativity difference between two atoms is, the shorter you can expect the bond to be, insofar as the electronegative atom is the same size as another comparable electronegative atom.
However, examining actual data, we would see that on average, in conditions without other bond polarizations occuring:
r
C
−
Cl
≈
177 pm
r
C
−
C
≈
154 pm
r
C
−
O
≈
143 pm
r
C
−
F
≈
135 pm
r
C
−
H
≈
109 pm
r
O
−
H
≈
96 pm
So it is not necessarily the least electronegativity difference that gives the longest bond.
Therefore, you cannot simply consider electronegativity. Examining the radii of the atoms, you should notice that chlorine is the biggest atom in the compound.
r
Cl
≈
79 pm
r
C
≈
70 pm
r
H
≈
53 pm
r
O
≈
60 pm
So assuming the answer is truly
C
−
C
, what would have to hold true is that:
The
C
−
F
bond polarization makes the carbon more electropositive (which is true).
The now more electropositive carbon wishes to attract bonding pairs from chlorine closer, thereby shortening the
C
−
Cl
bond, and potentially the
C
−
H
bond (which is probably true).
The shortening of the
C
−
Cl
bond is somehow enough to be shorter than the
C
−
C
bond (this is debatable).
Answer:
MgO.
Explanation:
charges of both satisfy one another (balanced) -- producing a compound MgO.
Answer:
0.087 moles of water
Explanation:
Given data:
Number of molecules of water = 5.24×10²² molecules
Number of moles of water = ?
Solution:
The given problem will solve by using Avogadro number.
1 mole = 6.022 × 10²³ molecules of water
5.24×10²² molecules × 1 mol / 6.022 × 10²³ molecules
0.87×10⁻¹ mol
0.087 mol
Avogadro number:
It is the number of atoms , ions and molecules in one gram atom of element, one gram molecules of compound and one gram ions of a substance. The number 6.022 × 10²³ is called Avogadro number.
Answer:
Mass in nuclear reactions is not strictly conserved due to this principle of mass and energy being quite similar. We know that nuclear reactions release a lot of energy. This energy, though, is actually mass that is lost from nucleons, converted into energy, and lost as the mass defect.
Some mass is turned into energy, according to E=mc2.
<em><u>Explanation:</u></em>
E=mc2 is probably the most famous equation. E is the energy, m is mass, and c is the constant speed of light. Einstein came up with it to show that energy and mass are proportional - one can turn into the other, and back again.
Mass in nuclear reactions is not strictly conserved due to this principle of mass and energy being quite similar. We know that nuclear reactions release a lot of energy. This energy, though, is actually mass that is lost from nucleons, converted into energy, and lost as the mass defect.
