Wait, do you mind clarifying what you would like answered for the question?
Since the container of the gas is rigid, the volume of the gas will remain constant. Therefore, when the number of particles were decreased in half then the pressure will also be half of the original given they both are subjected to the same temperature.
PV = nRT
V, T and R are constants so they can be lumped together to a constant k.
P/n = k
P1/n1 = P2/n2
since n2 = n1/2
P1/n1 = P2/<span>n1/2</span>
P2 = P1/2
“Metal ions are typically smaller than their corresponding neutral atoms”
Answer) Smaller
A grey coloured rock with amphibole and intermediate plagioclase like an andesine would classify as an intermediate rock by Bowen's Reaction Series and by the classification of igneous rocks would probably be like a diorite which is intermediate between a gabbro and a granite. A diorite essentially has no quartz but has the silicates amphibole (like hornblende), mica perhaps a little pyroxene and andesine plagioclase.