Answer : The chronological order events related to the formation of the universe with the stages in which they occurred are given below;
- Expansion from an infinitely hot point - Which is also called as the Planck era from which the big bang theory arrived. It is assumed that from the moment of initial expansion to
seconds afterwards, and many also refer that it was from an infinitely hot point. - Hydrogen fuses into helium - This was called as the era of Nucleosynthesis which resulted from the Fusion and it continued in the Era of Nucleosynthesis ( which is 0.001 seconds – 3 minutes)
- The first neutral atom begins to form - Era of atoms, it began in around 380,000 years – 1 billion years or so.
For better understanding please refer the attachment.
Answer:
Because X-rays have wavelengths similar to the size of atoms
Answer:
The fraction of the available octahedral positions are filled with
ions is 
Explanation:
If there are n numbers of spheres in HCP in packing:
Number of octahedral void = n
Number of tetrahedral void = 2n
Total number of voids = n + 2n = 3n
The
crystal structure consists of an HCP arrangement of
ions.
Number of spheres in HCP = 6
Number of
= 6
Number of octahedral voids = 6
Number of tetrahedral void = 12
Number of aluminum ions when there are 6
ion =
Number of voids in which
ions are present = 4
The fraction of the available octahedral positions are filled with
ions = 