Chapter 2.2

# Chapter 2.2 - Some simple calculations The number of atoms...

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5 MSE 2090: Introduction to Materials Science Chapter 2, Bonding The number of atoms per cm 3 , n, for material of density d (g/cm 3 ) and atomic mass M (g/mol): n = N av ×d ±/±M Graphite (carbon): d = 2.3 g/cm 3 , M = 12 g/mol n = 6×10 23 atoms/mol × 2.3 g/cm 3 / 12 g/mol = 11.5 × 10 22 atoms/cm 3 Diamond (carbon): d = 3.5 g/cm 3 , M = 12 g/mol n = 6×10 23 atoms/mol × 3.5 g/cm 3 / 12 g/mol = 17.5 × 10 22 atoms/cm 3 Water (H 2 O) d = 1 g/cm 3 , M = 18 g/mol n = 6×10 23 molecules/mol × 1 g/cm 3 / 18 g/mol = 3.3 × 10 22 molecules/cm 3 For material with n = 6 × 10 22 atoms/cm 3 we can calculate mean distance between atoms L = (1/n) 1/3 = 0.25 nm. ± the scale of atomic structures in solids – a fraction of 1 nm or a few A.

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6 MSE 2090: Introduction to Materials Science Chapter 2, Bonding Electrons in Atoms (I) Electrons move not in circular orbits, but in 'fuzzy‘ orbits. Actually, we cannot tell how it moves, but only can say what
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## Chapter 2.2 - Some simple calculations The number of atoms...

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