transition metals

• some of the transition metals are in the d-block of the periodic table
• transition element forms one or more stable ions with an incompletely filled d-orbital
• zinc and scandium are not transition elements as they do not form a stable ion with a partially filled d-subshell
• chromium and copper behave differently as the electron from the 4s orbital move into the 3d orbital to create a full or half full shell
• scandium ion has a empty d-sub shell
• zinc ion have a full d-sub shell
• characteristics of transition metals

  • shiny, strong and hard solids
  • high melting and boiling points
  • conductors of heat and electricity
• most common oxidation state is +2 as it is formed when the two electrons are lost in the 4s orbital - which makes it stable
• the maximum oxidation state involves the loss of all the 4s and 3d electrons
• ligands are species that can donate a lone pair of electrons to form a dative bond to the central metal ion such as chlorine and water
• complex ion is the central metal ion surrounded by ligands
• the coordination number is the number of coordinate bonds to the central atom
• complex ions are formed when ligands form coordinate bonds to vacant orbitals in the central atom
• the overall charge on a complex ion is the sum of charges on the central ion and each ligand in the complex
• to write formulas for complex ions you write the metal ion first then ligands, and the total charge goes outside the bracket
• monodentate ligands have only one atom capable of binding to a central metal atom such as water
• bidentate ligands have two atoms capable of binding to a central metal atom such as oxalate
• polydentate ligands have more than two atoms capable of binding to a central metal atom such as EDTA
• when a central metal ion is bonded to two ligands then it is linear
• when there are 6 ligands bonded to the central metal ion it is octahedral
• when central metal atom is bonded to 4 large ligands it is tetrahedral
• cisplatin and transplatin is a square planar even though it is bonded to 4 ligands
• the five d orbitals are described as degenerate - all at the same energy level
• when a metal forms a complex ion the dative bonds repel two orbitals, so there are now two d-orbitals that are slightly higher in energy levels compared to the other three
• an electron from the lower energy level can absorb energy to excite to the higher energy level. the movement from the lower to higher energy level is equal to the energy absorbed
• the energy absorbed by the electron is from the visible spectrum therefore the colors that are not absorbed is seen
• in s-block elements there are no visible colour as the the energy gap is too large to absorb visible light
• the colour changes in transition metal ions may happen as ligands can be exchanged to other ligands if it makes the complex ion more stable.
• the colour of the solution formed depends on what the transition metal is.
• colour changes can happen due to a change in oxidation number, ligand or the coordination number of the complex
• copper 2+ dissolved in water forms a blue solution, bonds with 6 water
• adding ammonium hydroxide to copper 2+ forms a pale blue precipitate, adding further excess ammonia forms a deep blue solution
• adding concentrate HCL to the copper solution drop by drop a yellow solution is formed, as the water is exchanged with chlorine
• nickel 2+ in water forms green solution
• adding ammonium hydroxide to the nickel solution forms a grey-green precipitate, adding further excess ammonia turns the precipitate blue
• adding concentrated HCL to the nickel solution, it will turn the solution yellow
• dissolving cobalt 2+ in water forms a pink solution
• adding sodium hydroxide to the cobalt solution will form a blue precipitate
• adding ammonia to the cobalt solution will form a yellow-brown solution
• concentrate HCL in cobalt solution will form a blue solution