Question

Between the atomic numbers $1,11,13$and $31$, which of these elements is the most metallic? Explain.

Answer 1

• The elements with atomic number $1,11,13$and $31$are Hydrogen $\left(\mathrm{H}\right)$, Sodium $\left(\mathrm{Na}\right)$, Aluminium $\left(\mathrm{Al}\right)$ and Gallium $\left(\mathrm{Ga}\right)$ respectively.
• Metallic character in the periodic table decreases from left to right in a period and increases from top to bottom in a group.
• Hydrogen and Sodium belong to group $1$, Aluminum and Gallium to group $13$.
• Group $1$ is more metallic than Group $13$ and referred to as the Alkali metals.
• Also, Hydrogen is a non-metal under normal conditions and Sodium, Aluminium, and Gallium are metals. So it will have low metallic character than the other three elements.
• Sodium has one valence electron. It gives away that electron to form ${\mathrm{Na}}^{+}$ion. On the other hand, Aluminium and Gallium have three electrons in the outer shell. So, they have to lose three electrons to become ${\mathrm{Al}}^{3+}$and ${\mathrm{Ga}}^{3+}$.
• The metallic character is determined when the elements lose electrons to form electropositive atoms. It is inversely proportional to the ionization enthalpy. Less the ionisation enthalpy, more is the metallic character.
• The ionization energy of Sodium is $5.14$, Aluminium is $5.98$, Gallium is $6.00$. Sodium has the least Ionization enthalpy which indicates it is more metallic. Thus, Sodium is more metallic than Hydrogen.

Hence, among the elements with atomic number $1,11,13$and $31$, the element with atomic number $11$ is the most metallic.