Sodium (located in the third period of the periodic table) has a principle quantum
number (n) of

3

Explanation: For example, sodium is in the third period of the table, so its principal quantum number is 3. Denote the principal quantum number as n and the second number, shape, is anywhere from 0 to n-1. So for sodium, the second quantum numbers are 0,1 and 2.

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.