ANSWER
2 valence electrons
STEP-BY-STEP EXPLANATION:
The electronic configuration is given below as

Looking at the configuration, you will see that the last energy carries 2 electrons
Hence, the valence electrons are 2
Answer:
Explanation:
Octet, in chemistry, the eight-electron arrangement in the outer electron shell of the noble-gas atoms. This structure is held responsible for the relative inertness of the noble gases and the chemical behaviour of certain other elements.
.5 mols
Assuming that your 2.0 m is an M for molarity
I used the formula M=number of mold/L
Converted 250mL to .250L by dividing by 1000
Hope this helps with the answer to your question
And the significant amount of volume can be differed by its solitude