Disproportionation occurs when an element in a specific oxidation state can be both oxidized and reduced. This requires the element to be in an intermediate oxidation state.

• In $BrO_{4}^{-}$, the oxidation state of Bromine is $+7$.
• Since $+7$ is the maximum possible oxidation state for Bromine, it cannot be oxidized further.
• Therefore, $BrO_{4}^{-}$ cannot undergo disproportionation.

The textbook traces the origin of commercial radio advertising to a specific event: “In 1922, a station in New York ran a 10-minute talk on the merits of some co-op apartments in Jackson Heights, N.Y. — and charged $50 for their effort. That was deemed a toll broadcast — now better known as a commercial.” The textbook later identifies this as station WEAF, New York on August 28, 1922, for the Queens Boro real estate corporation, voiced by H.M. Blackwell. This single broadcast established the principle that radio time could be sold to advertisers to reach audiences — creating the commercial broadcast model that would define American radio (and later television) for decades. This contrasts sharply with the BBC's licence-fee model (public funding) established in Britain in 1923, which sought to keep radio independent of commercial pressures.

Language Development Milestones:

Red flag at 18 months: No single words = speech delay — requires formal evaluation.

Critical distinction:

• This child maintains eye contact, points, plays peek-a-boo = social development intact → less likely autism
• Speech delay without social communication deficits suggests: hearing loss, expressive language delay, bilingual exposure, or oral-motor issues

First step: Formal hearing test (audiometry) — hearing loss is the most common correctable cause of speech delay. Concurrent speech-language evaluation.

Reassurance without evaluation at 18 months is inappropriate — early intervention improves outcomes significantly.