# Tutor profile: Alejandro C.

## Questions

### Subject: Material Science

For the FCC crystal structure, there are eight corner atoms (Nc = 8), six face atoms (Nf = 6), and no interior atoms (Ni = 0).

The number of atoms per unit cell, N, can be computed using the following formula N=Ni+\frac{Nf}{2}+\frac{Nc}{8} where Ni = the number of interior atoms Nf = the number of face atoms Nc = the number of corner atoms N=0+\frac{6}{2}+\frac{8}{8} = 4

### Subject: Inorganic Chemistry

Chromium has four isotopes,_{50}^{24}\textrm{Cr}, _{52}^{24}\textrm{Cr}, _{53}^{24}\textrm{Cr}, and _{54}^{24}\textrm{Cr}. How many electrons, protons and neutrons does each isotope possess?

Each isotope: 24 e, 24 p; 26, 28, 29 and 30 n, respectively.

### Subject: Chemistry

Calculate the wavelength in meters of an electron traveling at 1.24 x10^{7} \frac{m}{s}. The mass of an electron is 9.11x10^{-28} g

We use the Broglie equation: \lambda = \frac{h}{mv} where h (Planck´s constant) = h=6.626 x 10^{-34} \frac{kg.m^{2}}{s} Substituting into the de Broglie equation, m=9.11 x10^{-28} g = 9.11x10^{-31} kg \lambda = \frac{h}{mv} = \frac{6.626x10^{-34}\frac{kg.m^{2}}{s}}{\left ( 9.11x10^{31}kg \right )}{\left ( 1.24x10^{7} \frac{m}{s} \right )} = 5.87x10^{11}m

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