Engineering Materials Week 1

Engineering Materials Week 1
2.4-
(a) Cite two important quantum-mechanical concepts associated with the Bohr model of the atom.
Two important quantum-mechanical concepts associated with the Bohr model of the atom are that electrons are particles moving in discrete orbitals, and electron energy is quantized into shells.
(b) Cite two important additional refinements that resulted from the wave-mechanical atomic model.
Two important refinements resulting from the wave-mechanical atomic model are that electron position is described in terms of a probability distribution, and electron energy is quantized into both shells and sub shells-each electron is characterized by four quantum numbers.
2.13-
Calculate the force of attraction between a Ca2+ and an O2- ion the centers of which are separated by a distance of 1.25nm.

= 5.89  10-10 N

2.23-
Explain why hydrogen fluoride (HF) has a higher boiling temperature than the hydrogen chloride (HCl) (19.4 vs. -85 C) even though HF has a lower molecular weight.
HF is more polarized than HCl because F is more electronegative than Cl. Consequently, H - bonding will be significant in HF but very much less so in HCl. As a consequence, the boiling point of HF will be quite high for its molar mass