Question

Identify the metal associated with the weakest metallic bond.
A)Sodium
B)Gold
C)Mercury
D)Gallium

Answer 1

Metallic bonds are the type of bonds that are formed by the collective sharing of delocalized electrons and positively charged cations.

Complete step by step answer:
Metallic bonds are formed by sharing of metallic ions among the lattice structure of atoms.
We know that metals are made of positive ions closely packed together in crystalline solid. These positive ions of metals are surrounded by the negative valence electrons of the atom. These electrons are freely movable inside the lattice structure.
For example, sodium consists of 11 protons. 10 protons in the nucleus form the cation while 1 electron is allowed to roam free.
The metallic bonds are much weaker than the covalent and the ionic bonds.
These metallic bonds are responsible for the shining property of metals. The highly mobile sea of electrons absorbs the photons from light and jumps to higher energy levels. When this excited electron loses energy and falls to a lower energy level, it emits light.
The strength of metallic bond is dependent on the following factors:
Number of delocalized electrons on the lattice structure – More the number of delocalized electrons in the sea, stronger is metallic bond.
Magnitude of positive charge held by the ion – The greater the magnitude of charge, stronger is the metallic bonding.
Radii of cation – Smaller the ionic charge, Stronger is the metallic bonding, as smaller ions exert a greater force of attraction.
Now, the electronic configuration of metals
Sodium - $1s^{2} ,2s^{2} ,2p^{6} ,3s^{1}$
Gold – $[Xe]4f^{14} ,5d^{10} ,6s^{1}$
Mercury - $[Xe]4f^{14} ,5d^{10} ,6s^{2}$
Gallium – $[Ar]3d^{10} ,4s^{2} ,4p^{1}$
Sodium, Gold and Gallium - all have 1 delocalized electron in their electron pool,
However, the electronic configuration of Mercury is complete and hence it is less likely to be ionized.

Thus, Mercury forms weak metallic bonds.

Note:- Metallic Bonding is responsible for shiny appearance, malleability and other properties of metals. However, sodium metal is neither hard nor shiny. This is because most of the electrons shared by sodium in the pool possess positive charge.