Chromium can exhibit different valencies depending on the specific compound it is in. In the case of Cr2K2O7 (potassium dichromate), chromium is indeed in its 6th valency.
In Cr2K2O7, each chromium atom is in the +6 oxidation state (or valency). This means that each chromium atom has lost six electrons to achieve a +6 charge. The potassium (K) ions in the compound balance out this charge by providing a +2 charge each, resulting in two potassium ions for every chromium ion.
So, in Cr2K2O7, chromium is indeed in its 6th valency or +6 oxidation state, having lost six electrons.