How many Fluorine atoms are needed to accept the electrons of one Ca atom?
1
2
3
4

2 F atoms

Explanation:

A Ca atom has a valence number of +2, which means that when ionized, it will give up two electrons. In turn, a F atom has a valence number of -1, which means it can only accept 1 electron when ionized. So to accommodate the two electrons from Ca atom, we need 2 F atoms.

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.