Copper has a FCC i.e. face centered cubic crystal structure. The 100 plane is essentially a planar section of the cubic cell where 4 Cu atoms occupy the 4 corners of the plane along with 1 Cu atom at the center of that plane. Each of the Cu atoms in the corners is shared by 4 adjacent unit cells. Thus, there are 2 Cu atoms present in the 100 plane (4*1/4 + 1 = 2).
Now, the planar density PD along the 100 plane is given as:
PD(100) = # atoms in the 100 plane/Area of 100 plane
=
Here R = radius = 0.128 nm = 
PD = 
Hypothesis
Therefore the last step in the scientific method is proposing a hypothesis or obtaining a conclusion
Answer:
2,5
Explanation:
When move from left to right in periodic table atomic number increases. So element to the right of carbon has one electron more than carbon therefore it's electronic configuration would be 2,5