Rutherford and Bohr

Given the hugely significant advances made by Ernest Rutherford and Niels Bohr in our understanding of the atom, they were obvious choices when it came to naming some of the more recently discovered elements. But the right to name these new elements was controversial and rooted in the Cold War. They remained without definitive names for some years, though one thing was certain: both the Russian and US scientists felt that Rutherford deserved the honour. What they couldn’t agree on was which element should carry his name. Three different elements were proposed; eventually the disputes were resolved and element 104 became rutherfordium, with 107 named bohrium.

Ernest Rutherford was born and grew up in New Zealand, hence the silver fern to represent his element. He worked in the early part of the 20th century in Cambridge, Montreal and Manchester, during which time he: discovered that atoms could disintegrate (the basis of radioactivity, for which he was awarded the Nobel Prize in Chemistry in 1908); distinguished between alpha and beta radiation; established the existence of the atomic nucleus and formulated his model of the atom; identified gamma radiation; discovered the proton; and proposed the existence of the neutron – not a bad list of career accomplishments.

Rutherford’s model of the atom with its mass concentrated in a central nucleus was a significant advance on Thomson’s plum pudding model where the negatively-charged electrons were evenly distributed, like raisins, in a positively charged ‘pudding’. It was Danish physicist Niels Bohr who took Rutherford’s model one step further and proposed that the electrons surrounding the nucleus occupy distinct orbits, explaining why atoms emit light at fixed wavelengths. He was awarded the Nobel Prize in Physics for this work in 1922.

Bohr went on to formulate the complementarity principle as a conceptual basis of quantum mechanics. It holds that phenomena can exhibit contradictory but complementary properties that cannot be observed simultaneously, for example, the wave and particle characteristics of light. In 1947, King Frederik IX of Denmark conferred upon Bohr the Order of the Elephant. This is Denmark’s highest honour and rarely given to anyone other than royalty and heads of state. It entitled Bohr to his own coat of arms; he chose the yin-yang symbol and the motto contraria sunt complementa‘ – opposites are complementary.

With thanks to Jens Sveistrup, my consultant on all things Danish, for suggesting the yin-yang symbol.

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