Basic/stupid question. Why does 'b' sound odd within this scale/root

[maudioradium]

Hi,

I'm playing around on the keys after a long time and confused about something - warning, I'm only learning the basics.

If starting with F and working down the white keys, to my ears, the following keys sound correct together
F, E, D, C, A, G, F, D, or
F, E, D, C, A, G, F, E, D

Questions:
1. When including the B, it is 'out'. I assume this is because it isn't part of a typical/established scale.
2. Can someone tell me what I'm doing here and what scale/key etc I'm in?

Thanks.

[cryophonik]

Try it with B-flat and report back if it sounds “right” to you

[NAD]

The most common and natural sounding type of scale to western listeners (i.e. most of us) is the major scale. The F major scale includes all the white keys except for B which is replaced with a Bb (the black key immediately to the left of the B key). So when you start descending on the white keys from F, by the time you get the B your ear is already primed to hear an F major scale so the B (which is not in key) clashes with what you ear is "expecting" to hear (Bb).
I recommend you try looking up videos explaining how the major scale is constructed and try to learn how to find the notes in a particular key by comparing with the intervals of C major.

[Farnaby]

If you play the B natural in your example you are playing the descending scale of the Lydian mode rather than the F major scale. This is sometimes used in music but as said above is nowhere near as common.