Assertion: protactinium's number | /r/CapableOf | contribute increase
Facets:
value: from one in francium
type: LOCATION
Source sentences:
text: At the start of period 7, from francium to thorium, the melting points of the elements increase (as in other periods), because the number of delocalised electrons each atom contributes increases from one in francium to four in thorium, leading to greater attraction between these electrons and the metal ions as their charge increases from one to four.