Editing Group 4 element (section)

{{Short description|Group of chemical elements}}
{{Infobox periodic table group
| title       = Group&nbsp;4 {{nowrap|in the periodic table}}
| group number= 4
| trivial name=
| by element  = titanium group
| CAS         = IVB
| old IUPAC   = IVA
| mark        = Ti,Zr,Hf,Rf
| left        = [[Group 3 element|group 3]]
| right       = [[Group 5 element|group 5]]}}
{| class="floatright"
! colspan=2 style="text-align:left;" | ↓&nbsp;<small>[[Period (periodic table)|Period]]</small>
|-
! [[Period 4 element|4]]
| {{element cell image|22|Titanium|Ti| |Solid|Transition metal|Primordial|image=Titan-crystal bar.JPG|image caption=Titanium crystal bar}}
|-
! [[Period 5 element|5]]
| {{element cell image|40|Zirconium|Zr| |Solid|Transition metal|Primordial|image=Zirconium crystal bar and 1cm3 cube.jpg|image caption=Zirconium crystal bar}}
|-
! [[Period 6 element|6]]
| {{element cell image|72|Hafnium|Hf| |Solid|Transition metal|Primordial|image=Hf-crystal bar.jpg|image caption=Hafnium crystal bar}}
|-
! [[Period 7 element|7]]
| {{element cell image|104|Rutherfordium|Rf| |Unknown phase|Transition metal|Synthetic}}
|-
| colspan="2"|{{hr}}''Legend''<div class="center">
<div style="border:{{element color|Primordial}}; background:{{Element color|table mark}}; padding:0 2px;">[[primordial element]]</div>
<div style="border:{{element color|Synthetic}}; background:{{Element color|table mark}}; padding:0 2px;">[[synthetic element]]</div>
</div>
|}

'''Group 4''' is the second group of [[transition metal]]s in the periodic table. It contains only the four elements [[titanium]] (Ti), [[zirconium]] (Zr), [[hafnium]] (Hf), and [[rutherfordium]] (Rf). The group is also called the '''titanium group''' or '''titanium family''' after its lightest member.

As is typical for early transition metals, zirconium and hafnium have only the group [[oxidation state]] of +4 as a major one, and are quite electropositive and have a less rich coordination chemistry. Due to the effects of the [[lanthanide contraction]], they are very similar in properties. Titanium is somewhat distinct due to its smaller size: it has a well-defined +3 state as well (although +4 is more stable).

All the group 4 elements are hard. Their inherent reactivity is completely masked due to the formation of a dense oxide layer that protects them from corrosion, as well as attack by many acids and alkalis. The first three of them occur naturally. Rutherfordium is strongly [[radioactive]]: it does not occur naturally and must be produced by artificial synthesis, but its observed and theoretically predicted properties are consistent with it being a heavier homologue of hafnium. None of them have any biological role.