Answer to Question #287446 in Material Science Engineering for jay

Question

A.        What is meant by the term: atomic structure?

B.       State Pauli's Exclusion principle

C.          Write the electronic configuration for the following:

         Neon [Ne - 10]

Argon [Ar - 18]

D.  Sodium chloride (NaCl) exhibits predominantly ionic bonding. The [Na - 11]+ and [Cl — 17]- ions have electron structures that are identical to which two inert gases?

                                                                                                                

E. Clearly show that the atomic packing factor of face-centred cubic structure is 0.74.

Calculate the radius of a barium atom, given that Ba has a BCC crystal structure, a density of 3.6.g/cm³ and an atomic weight of 137 g/mol.

Answer 1

A. Atomic structure refers to the structure of an atom comprising a nucleus (centre) in which the protons (positively charged) and neutrons (neutral) are present. The negatively charged particles called electrons revolve around the centre of the nucleus.

B. Pauli's Exclusion Principle states that no two electrons in the same atom can have identical values for all four of their quantum numbers. In other words, (1) no more than two electrons can occupy the same orbital and (2) two electrons in the same orbital must have opposite spins.

C. Ne 1s²2s²2p⁶

Ar 1s²2s²2p⁶3s²3p⁶

D. Na⁺ 1s²2s²2p⁶ = Ne

Cl^- 1s²2s²2p⁶3s²3p⁶ = Ar

E.

In BCC there are 2 atoms per unit cell, so

2/a³ = N_A/V_molar , where V_molar = A/ρ; A is the atomic mass of Ba.

2/a³ = N_A x ρ / A

a = (2A / N_A x ρ)^1/3 = (2 x 137 / 6.02 x 10²³ x 3.6) = 5.02 x 10^-8 cm