The Hidden World of the Atom

Last November, A Level Physics students from Hatch End High went to a lecture at the University College London. There, Dr. Robert Palgrave delivered a mesmerizing lecture on the Hidden World of Atoms. Dr Palgrave started the lecture by introducing the great Michael Faraday’s example of a burning candle flame to explain modern chemistry.

That seemingly modest reaction is summarized here: CnH(2n+2) (s) + {(3n+1)/2}O2 (g) → n CO2 (g) + (n+1)H2O (g)

Many of the students in the auditorium that evening were wondering, how do we know that atoms are structured and behave in the way we see them in textbooks? The lecture took us on a history tour starting as early as antiquity. Democritus, the ancient Greek philosopher, considered the fundamental question on the nature of matter. He imagined a very large block of gold, which he cut it into half repeatedly. The question he posed was: “Is there ever a point where the block of gold can’t be cut any further?”. The people who thought the block could not be divided were called atomists and thus, they called the smallest unit of matter “the atom” (Greek: a + tomos = not cut). On the other hand, those who disagreed with Democritus could not accept the fact that there were gaps between atoms, which contained nothing.

Dr Palgrave then steered us into the 1880s, an era of rampant discovery in chemistry. Joseph Priestly discovered oxygen and nitrous oxide (commonly known as laughing gas). His contemporary and equal, Henry Cavendish would discover hydrogen in this period, calling it “inflammable air”. Astutely, Cavendish realized that no matter the amount of product made, the reactants always reacted in a certain proportion with each other. John Dalton (shown) lay down the foundations for modern atomic theory – his postulates said the states of matter (solids, liquids, and gases) are composed of discrete, indivisible units called atoms. Elements (like Cavendish’s hydrogen) are composed of atoms of the same mass and properties, and chemical reactions simply are the rearrangement of these atoms.

Dr Palgrave then entertained us with the story of August Kekule, a German organic chemist, who was the first person to solve the structure of benzene - a problem which had been troubling chemists for decades. The legend goes that whilst Kekule was asleep in front of the fire, he had a dream of a snake devouring its own tail. Upon waking, Kekule had the idea of the circular structure of benzene (shown). As Dr Pelgrave brought his lecture to a close, he arrived at his conclusion. The truth about the hidden world of atoms becomes clear: the accuracy and usefulness of scientific models of atoms have improved over time. Science is the relentless and rigourous pursuit of better and better models to explain the natural world.

Written by Monishka Sinha(6HME).