Electronegativity (EN) is a property that describes an atom’s attraction for electrons in a bond. This property determines the type of bond which forms between two atoms. An atom with a higher electronegativity means it has more attraction for electrons in a bond. Flourine has the highest electronegativity and is assigned a value of around 4. The periodic trend for electronegativity is that it increases as you go up and to the right of the periodic table.
The difference in electronegativity between the two bonding atoms is calculated to determine the bond type. There is a general scale used to determine the bond types. If the difference in electronegativity is between 3.3 – 1.7, the bond is ionic. If the difference is from 0 – 1.7, the bond is covalent. More specifically, if it is between 0 – 0.5, the bond is non-polar covalent. A polar covalent bond is formed between 0.5 – 1.7.
Molecular Range: 0 – 1.7
– Non-polar covalent: 0 – 0.5
– Polar covalent: 0.5 – 1.7
Ionic Range: 1.7 – 3.3
1) Na and Cl
Electronegativity of Na = 0.93
EN of Cl = 3.16
Difference in EN = 3.16 – 0.93 = 2.23
Therefore, the bond is ionic.
2) H and O
EN of H = 2.2
EN of O = 3.44
Difference in EN = 3.44 – 2.2 = 1.24
Therefore, the bond is polar covalent.
3) N and O
EN of N = 3.04
EN of O = 3.44
Difference in EN = 3.44 – 3.04 = 0.4
Therefore, the bond is non-polar covalent.
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