We have been able to predict properties of elements that had not been isolated yet. Your definition is too narrow.
Notably they do.
You wanna go another lap around the circle or?
> A prediction (from Latin prae- 'before' and dictum 'something said')[1] or forecast is a statement about a future event or about future data.
Troll muted.
"We predict that these properties will be found." -- about future events or data.
Trolls are stupid and dishonest losers. The end ... I won't be back.