# Chemistry, DM Revision Notes

###### Contents:
• 1 DM1
• 1.1 d-Block Elements
• 1.2 Electronic Configuration

## DM1

### d-Block Elements

• Chemistry of d-block is different to that of other elements

• Results from electronic configurations

### Electronic Configuration

• 4s fills and empties before the 3d orbital

• As the 4s orbital is filled, the transition metals in a period have the same valence electrons; except from Copper and Chromium

• Lower energy to remove an electron from the 4s orbital

Electron Configurations
Chromium and copper are different due to their being more stable arrangements for their electrons. Both of them only have one electron in the 4s orbital. For chromium, this avoids by pairing. For copper, the lowest energy state is given by pairing electrons in the 3d orbital instead.

Transition metals are those that form one or more stable ions with incompletely filled d-orbitals. Hence, zinc and scandium are not transition metals.

• Transition metals may have variable oxidation states

• Several stable arrangements for d and s electrons

## Redox Titrations

• Iron content can be analysed

• Potassium Manganate (VII) is a very strong oxidising agent

• End point is the pink colour of $$MnO_{4}^{-}$$

\begin{gather*} Fe^{(2+)}\Rightarrow Fe^{(3+)}+e^{-} \\ MnO_{4}^{-}+8H^{+}+5e^{-}\Rightarrow Mn^{(2+)}+4H_{2}O \\ 5Fe^{(2+)}+MnO_{4}^{-}+8H^{+}\Rightarrow 5Fe^{(3+)}+Mn^{(2+)}+4H_{2}O \\ \end{gather*}