(i) All the transition elements are metals, since the number of electrons in the outermost shell is very small being equal to `2`.

(ii) They are hard, malleable and ductile, except `Hg` which is liquid and soft.

(iii) They exhibit all the three types of structures. Face Centred Cubic (fcc), Hexagonal Close packed (hcp) and Body Centred Cubic (bcc).

(iv) Covalent and Metallic bonding both exist in the atom of transition metals.

(v) The presence of unfilled `d`-subshell favour covalent bonding, and metallic bonding is due to possession of one or two electron in outermost energy shell.

(vi) These metals are good conductors of heat and electricity.

(i) The transition elements have very high melting & boiling points as compared to those of `s` & `p` block elements.

(ii) The high melting and boiling point of transition metals are attributed to the stronger force that bind their atoms together.

(iii) As the number of `d`-electron increases the number of covalent bond between the atoms are expected to increase up to `Cr- Mo-W` family where each of the `d`-orbital has only unpaired electrons and the opportunity for covalent sharing is greatest.

(iv) lnspite of presence of five unpaired electrons in `Mn`, the unexpected low melting and boiling is due to its complex structure it is unable to form metallic and covalent bonds.

(v) The absence of unpaired electron `[(n- 1) d^10 4s^2]` in `Zn`, `Cd`, & `Hg` is responsible for its low melting & boiling point.

The value of these radii decreases generally, on moving from left to right in the period(See table 1).

`text(Reason)` :

(i) This is due to the fact that an increase in the nuclear charge tends to attract the electron cloud inwards.

(ii) The radii for the elements from `Cr` to `Cu` are however very close to one another.

(iii) The simultaneous addition of electron of `3d`-level exercises the reverse effect by screening the outer `4s`-electron from the inward pull of the nucleus.

(iv) As a result of these two opposing effects, the atomic radii do not alter much on moving from `Cr` to `Cu`.

(v) The radii of `M^(2+)` ions, although some what smaller than that of `Ca^(2+)` ion `(= 0.99 A^o)` are comparable with it.

`text(Oxides)` :

(i)Thus `MO` oxides of transition element should be similar to `CaO` in many ways, although some what less basic and less soluble in water(See fig.).

(ii)Similarly the Hydration energy of `M^(2+)` ion `[Ti^(2+) -> Cu^(2+)]` are between `446 kcal` to `597 kcal` is some what greater than that of `Ca^(2+)` ion `[ 395 kcal]`.

(i) The first ionisation potential of transitional elements lie between those of `s` & `p` block elements.

(ii) The first ionization potential of all the transition elements lie between `6` to `10` `text(eV)`.

(iii) In case of transition elements the addition of the extra electron in the (`n- 1`)`d` provides a screening effect which shields the outer `ns` electron from the inward pull of positive nucleus.

(iv) Thus the effect of increasing nuclear charge & the shielding effect created due to the expansion of (`n- 1`) `d` orbital oppose each other.

(v) On account of these counter affects, the ionisation potentials increases rather slowly on the moving in a period of the first transition series.

(vi) The `IE_1` for the first four `3d`-block elements (`Sc`, `Ti`, `V` & `Cr`) differ only slightly from one another.

(vii) Similarly the value of `Fe`, `Co`, `Ni` & `Cu` also are fairly close to one another.

`text(Colour: (aquated))`

`Sc^(3+) ->` `text(colourless)`
`Ti^(4+) ->` `text(colourless)`
`Ti^(3+) ->` `text(purple)`
`V^(4+) ->` `text(blue)`
`V^(3+) ->` `text(green)`
`V^(2+) ->` `text(violet)`
`Cr^(2+) ->` `text(blue)`
`Cr^(3+) ->` `text(green)`
`Mn^(3+) ->` `text(violet)`
`Mn^(2+) ->` `text(light pink)`
`Fe^(2+) ->` `text(light green)`
`Fe^(3+) ->` `text(yellow)`
`Co^(2+) ->` `text(pink)`
`Ni^(2+) ->` `text(green)`
`Cu^(2+) ->` `text(blue)`
`Zn^(2+) ->` `text(colourless)`

`text(Relative stability of various oxidation states)` : See fig.1

(i) The relative stabilities of various oxidation states of `3d`- series element can be correlated with the extra stability of `3d^(10)`, `3d^5` & `3d^(10)` configuration to some extent.

`text(Example)` - `Ti^(4+) (3d^0)` is more stable than `Ti^(3+) ( 3d^1)`

`Mn^(2+) ( 3d^5)` is more stable than `Mn^(3+) ( 3d^4).`

(ii) The higher oxidation state of `4d` and `5d` series element are generally more stable than those of the element of `3d` series.

`text(Example)` -

(a) `Mo text( )^(vi)O_4^(-2)`(`4d`-series element) & `W text( )^(vi)O_4^(-2)` , `Re text( )^(vii)O_4^(-)`(`5d-` series elements) are more stable
and in which the transition element concerned show their maximum oxidation state.

(b) `Cr text( )^(vi)O_4^(-)` & `Mn text( )^(vii)O_4^-` ( `3d`-series) are strong oxidizing agents.

(iii) Strongly reducing states probably do not form fluorides or oxides, but may well form the heavier halides. Conversely, strong oxidizing state form oxides & fluoride, but not Bromide and Iodide.

`text(Example)`-

(a) `V` react with halogens to form `VF_5`, `VCl_4`, `VBr_3`, but doesn't form `VBr_5` or `VI_5` because in `+5` oxidation state `V` is strong oxidizing agent thus convert `Br^(-)` & `I^(-)` to `Br^2` & `I_2` respectively, So `VBr_3` & `VI_3` are formed but not `VBr_5` & `VI_5`

(b) On the other hand `VF_5` is formed because `V^(+5)` ion unable to oxidize highly electronegative & small anion `F^-`.

(c) Similarly highly electronegative and small `O^(2-)` ion formed oxides eg. `VO_4^(3-), CrO_4^(2-) & MnO_4^(-)` etc.

(iv) All transition elements in their lower oxidation state like to fonn ionic compounds. Whereas in their higher oxidation state they generally formed covalent compound.

`text(Example)` : See fig.2