How can I know the melting point and the boiling point of an element?like, the further the outermost electron is far from the nucleus the more...

you can also estimate them. Just look at one element and
look at the boiling/melting point of all the 4 other elements that surround the element
you want to know the boiling/meling point. To the Left, Right, Top, and bottom of it.
You take those boiling/melting points and average them out. You'll get close to the
actual number.

its easier to look on the internet for
them...but you can use this method if you already know the other mlting/boiling
points.