The element which has the strongest metallic bond among ${\mathrm{ }}_{11}{\mathrm{A}}^{23}$ , ${ }_{12}{\mathrm{B}}^{24}$ ,${\mathrm{ }}_{13}{\mathrm{C}}^{27}$ and ${\mathrm{ }}_{19}{\mathrm{D}}^{39}$ is:

The metallic bond can be called the chemical bond that arises from the electrostatic forces between the electrons of the metal.

In this bond, the delocalized electrons lie in the pool of positively charged ions.

The strength of a metallic bond depends on the number of valence electrons. More the valence electrons, the stronger the metallic bond.

Now, to determine the strongest metallic bond, first find the number of electrons and then write their electronic configuration to find the number of valence electrons.

• ${ }_{11}{A}^{23}$has 11 electrons, thus its electronic configuration is$1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^1$
  Therefore, it has 1 valence electron.
• ${ }_{12}{B}^{24}$has 12 electrons, thus its electronic configuration is  $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^2$ . Therefore, it has 2 valence electrons.
• ${ }_{13}{C}^{27}$has 13 electrons, thus its electronic configuration is  $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^1$. Therefore, it has 3 valence electron.
• ${ }_{19}{D}^{39}$has 19 electrons, thus its electronic configuration is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}3{\mathrm{s}}^1$Therefore, it has 1 valence electrons.

As C has the highest number of valence electrons, that means it forms the strongest metallic bond.