Electronegativity Calculator

What is an Electronegativity?

Electronegativity shows how strongly an atom attracts shared electrons in a chemical bond. A higher value means stronger attraction toward bonding electrons.

Electronegativity Scales

Chemists use different electronegativity scales to compare atoms. The Pauling scale is most common in basic chemistry. Mulliken uses ionization energy and electron affinity. Allred Rochow uses nuclear charge and atomic radius.

Pauling Electronegativity Scale

The Pauling scale gives each element an electronegativity value. You normally look up these values instead of calculating them. For two atoms, use $\Delta\chi = |\chi_1 - \chi_2|$. Fluorine has the highest common value at about 3.98.

Mulliken Electronegativity Scale

The Mulliken scale uses two atomic properties. These are ionization energy and electron affinity. Its formula is $\chi_M = (I + A) / 2$. Here, $I$ is ionization energy and $A$ is electron affinity. Both values usually use the same energy unit.

Allred Rochow Electronegativity Scale

The Allred Rochow scale connects electronegativity with nuclear attraction and atomic size. Its common formula is $\chi_{AR} = 0.359Z_{eff}/r^2 + 0.744$. Here, $Z_{eff}$ is effective nuclear charge and $r$ is covalent radius in angstroms.

What is electropositivity?

Electropositivity describes how easily an atom gives up electrons. Metals often show higher electropositivity, while nonmetals usually attract bonding electrons more strongly.

Electronegativity Trend on the Periodic Table

Electronegativity usually increases from left to right across a period. It usually decreases down a group because atomic size increases and outer electrons sit farther from the nucleus.

How to calculate Electronegativity manually

You can compare atoms manually by using an electronegativity scale. For most school chemistry problems, start with the Pauling values and calculate their difference.

Using the Pauling Scale

Formula

The Pauling scale gives standard electronegativity values for elements. To compare two atoms, use $\Delta EN = |EN_1 - EN_2|$.

Step by step guide

1. Find the Pauling value for the first atom.
2. Find the value for the second atom.
3. Subtract the smaller value from the larger value.
4. Use the ΔEN result to classify the bond.

Practical Example

For Na and Cl, use $EN_{Na}=0.93$ and $EN_{Cl}=3.16$. Therefore, $\Delta EN=|0.93-3.16|=2.23$. This suggests an ionic bond under common classroom rules.

Using the Mulliken Scale

Formula

The Mulliken scale uses ionization energy and electron affinity. Its formula is $\chi_M=(I+A)/2$. Both values must use the same energy unit.

Step by step guide

1. Find the atom's ionization energy.
2. Find its electron affinity.
3. Add both values together.
4. Divide the total by two.
5. Use the result as the Mulliken electronegativity.

Practical Example

Suppose an atom has $I=10$ eV and $A=2$ eV. Then $\chi_M=(10+2)/2=6$ eV. This value represents the atom's Mulliken electronegativity.

Using the Allred Rochow Scale

Formula

The Allred Rochow formula uses effective nuclear charge and covalent radius. A common form is $\chi_{AR}=0.359Z_{eff}/r^2+0.744$.

Step by step guide

1. Find the atom's effective nuclear charge.
2. Find its covalent radius in angstroms.
3. Square the covalent radius.
4. Divide $Z_{eff}$ by $r^2$.
5. Apply the formula to get electronegativity.

Practical Example

If $Z_{eff}=4$ and $r=1.0$ Å, then $\chi_{AR}=0.359(4)/1^2+0.744=2.18$. This demonstrates the calculation method.

How to Calculate Electronegativity Difference

Formula

Electronegativity difference measures how far apart two atoms are on an electronegativity scale. Use $\Delta EN=|EN_1-EN_2|$.

Step by step guide

1. Find the electronegativity value for atom one.
2. Find the value for atom two.
3. Subtract one value from the other.
4. Ignore the negative sign by taking the absolute value.
5. Compare ΔEN with common bond classification ranges.

Practical Example

Hydrogen has $EN=2.20$, while chlorine has $EN=3.16$. Therefore, $\Delta EN=|2.20-3.16|=0.96$. This commonly indicates a polar covalent bond.