Largest possible rocky planet

[sandcastles]

Early in the history of an Earthlike planet, one or more large impacts, especially by bodies larger than Mars, could have rid it of its lighter elements, especially hydrogen and helium? Then any fragments would eventually reassemble to form a planet (with or without a large moon)?
Varieties of carbonyls could predominate. Since they have different freezing and boiling points, there would be plenty of variable, foggy weather.