Question

Which elements in the third period will have the lowest and highest electronegativities? Explain.

Answer 1

• Electronegativity is the tendency of an element to attract the shared pair of electrons towards itself. In the periodic table, the electronegativity increases from left to right and decreases from top to bottom in the group.
• There are eight elements in the third period, namely- Sodium $\left(\mathrm{Na}\right)$, Magnesium $\left(\mathrm{Mg}\right)$, Aluminium $\left(\mathrm{Al}\right)$, Silicon $\left(\mathrm{Si}\right)$, Phosphorus $\left(\mathrm{P}\right)$, Sulphur$\left(\mathrm{S}\right)$, Chlorine $\left(\mathrm{Cl}\right)$ and Argon $\left(\mathrm{Ar}\right)$.
• In a period, the atomic number increases from left to right, so the number of valence electrons also increases. More the number of valence electrons in an atom more is its tendency to attract the shared electron.

1. Argon does not form any covalent bond as it has a filled valence shell. So, it has zero electronegativity.
2. Chlorine has the maximum number of valence electrons (7), so it is highly inclined toward attracting the electron.

• Thus, the order of Electronegativity in the third period is $\mathrm{Ar}<\mathrm{Na}<\mathrm{Mg}<\mathrm{Al}<\mathrm{Si}<\mathrm{P}<\mathrm{S}<\mathrm{Cl}.$
• Hence, the elements in the third period that have the lowest, and highest electronegativities are Argon and Chlorine respectively.