Question

What are `"metallic properties"`, and how do these arise on account of `"metallic bonding"`?

Answer 1

So what are the properties of metals?

Explanation:

I can think of 4 defining characteristics:

`(i)` `"metals are malleable; they can be beaten out into a sheet"`

`(ii)` `"metals are ductile; they can drawn out into a wire"`

`(iii)` `"metals tend to be good conductors of heat"`

`(iv)` `"metals tend to be good conductors of electricity"`

And metallic bonding is typically described as `"positive ions in a sea of electrons"`. Here, a close-packed array of metal atoms, each donate 1, or 2, (or more) electrons to the entire lattice (and these are the so-called valence electrons). The metal ions, which are of course positive because of their electron deficiency, are attracted to the electron sea, and the non-directionality, and non-molecularity of the attraction results in the given properties.

Metals atoms within the lattice can thus move with respect to each other, WITHOUT disrupting the electrostatic bonding interaction, the which is based on free electrons that can move across the entire lattice (and transfer heat or charge!). Metals also typically exhibit metallic lustre, for which the delocalized electrons are also held to be responsible.

Answer 2

Using metallic bonding we can explain many characteristics of transitional elements.

MELTING & BOILING POINTS

The transitional metals have high M.P & B.P.
Their M.P rise to maximum and then fall as the atomic number`uarr`

Strong metallic bonds{M.B} between the atoms of these elements are responsible for higher M.P and B,P.

As unpaired electrons increases the M.B in that atom `uarr`

As we know the amount of unpaired electrons `uarr`upto Mn and then decreases{paired up}.Similarly Metallic bonding `uarr` upto Mn and then decreases as M.B`prop`unpaired electrons.
You should remember that " Greater the no. of unpaired electrons greater the Metallic bonding".

{`rarr`Dip of Mn{ as you can see in graph }although it has 5 unpaired electrons{max in 3d series} is explained on the basis of exactly half filled d orbitals `rarr` stable and electrons tightly held and less delocalisation and thus weak M.B. Similar for Tc{4d} and Re{5d}.}

HARDNESS & OTHER PHYSICAL PROPERTIES
`rarr`can be explained using M.B.

As unpaired electrons `uarr` hardness of the metal increases.
for eg: Cr, Mo ,and W have maximum no, of unpaired d electrons and therefore are hard metals whereas Zn ,Cu ,and Hg are not very hard metals due to absence of unpaired electrons and thus weak M.B.

hope it helps.