Assertion: einsteinium's electron | /r/CapableOf | ionize before the 5f ones
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text: The first ionization potential of mendelevium was measured to be at most (6.58 ± 0.07) eV in 1974, based on the assumption that the 7s electrons would ionize before the 5f ones; this value has since not yet been refined further due to mendelevium's scarcity and high radioactivity.