Physics atom problem??

Question

N type doped silicon has 5.1x10^28 silicon atoms per m³. Given that only 1 in 200000 atoms is replaced by the doping element, how many electrons per m³ are there?

Answer 1

5.1x10^28 x 4
=2.04x10^29

2.04x10^29 / 200000
=1.02x10^24

2.04x10^29+1.02x10^24
=2.0400102x10^29 m³

Answer 2

Given the very small ratio of non-silicon to silicon elements, we can just take it all to be silicon (specifically, we have a 1 in 100 part inaccuracy in the number of atoms per cubic metre anyway, so an additional factor of the order of 1 in 200,000 will make absolutely no difference).
Silicon is element 14, so each of those atoms has 14 electrons. So the number of electrons per cubic metre is 14 × 5.1×10^28 = 7.1×10^29.

Answer 3

Given the very small ratio of non-silicon to silicon factors, we are able to easily take all of it to be silicon (specifically, we've a a million in one hundred area inaccuracy in the style of atoms in line with cubic metre besides, so one extra element of the order of a million in 2 hundred,000 will make actually no distinction). Silicon is factor 14, so each and each of those atoms has 14 electrons. So the style of electrons in line with cubic metre is 14 × 5.a million×10^28 = 7.a million×10^29.

Answer 4

In this case, it is a matter of following the units. In the expression below, it is a matter of cancelling the number of Si atoms and leaving the answer in units of conduction electrons / m³.

(5.1e28 Si atoms) / (1 m³) * (1 conduction electron) / (2.0e5 Si atoms)
= 2.6e23 conduction electrons per m³