David Berlo's SMCR (Source-Message-Channel-Receiver) Model places heavy emphasis on the communication skills of both the source/encoder and the receiver/decoder. According to Berlo:

• Encoding skills (producing messages): Speaking and Writing
• Decoding skills (receiving messages): Listening and Reading
• Skill common to both encoding and decoding: Thought or Reasoning — the intellectual capacity to analyse intentions and translate them into appropriate language or interpret received language accurately

Berlo also stressed the dyadic (two-party, relationship-based) nature of communication: the same skill level in a source might succeed with one receiver but fail with another because the receiver's skill, knowledge, attitude, and socio-cultural background differ. This makes fidelity — the degree to which the received message matches the intended message — the key measure of communication quality.

$[\text{Cr(H}_2\text{O)}_6]\text{Cl}_3$: H$_2$O is neutral, Cl$^-$ is $-1$, complex has charge 3+. So Cr = +3.

$[\text{Cr(C}_6\text{H}_6)_2]$: Benzene is a neutral ligand (0 charge). Complex is neutral. So Cr = 0.

$\text{K}_2[\text{Cr(CN)}_2(\text{O})_2(\text{O}_2)(\text{NH}_3)]$: K$^+$ gives $+2$ outside; complex ion has $-2$ charge. CN$^-$ ($-1$ each, $2\times-1=-2$); O$^{2-}$ ($-2$ each, $2\times-2=-4$); O$_2^{2-}$ (peroxo, $-2$); NH$_3$ (0). Let Cr = $x$: $x + (-2) + (-4) + (-2) + 0 = -2 \Rightarrow x - 8 = -2 \Rightarrow x = +6$.

Oxidation states: +3, 0, +6.