Calculating the Number of Electrons:
To determine the number of electrons flowing through a metallic wire, we need to consider the relationship between current, time, and charge. The equation Q = It relates charge (Q) to current (I) and time (t), where Q is measured in coulombs (C), I is measured in amperes (A), and t is measured in seconds (s).

Converting Time to Seconds:
Given that the current is 0.5 amperes and it flows for 2 hours, we need to convert the time to seconds as the standard SI unit for measuring time in electrical calculations is seconds.

1 hour = 60 minutes
1 minute = 60 seconds

Therefore, 2 hours is equal to 2 x 60 x 60 = 7200 seconds.

Calculating the Charge:
Using the equation Q = It, we can calculate the charge by multiplying the current (0.5 A) by the time (7200 s):

Q = 0.5 A x 7200 s
Q = 3600 C

Thus, the charge passing through the wire is 3600 coulombs.

Calculating the Number of Electrons:
To find the number of electrons, we need to know the charge of a single electron. The elementary charge (e) is equal to 1.6 x 10^-19 coulombs.

Number of electrons (N) = Total charge (Q) / Charge of a single electron (e)

N = 3600 C / (1.6 x 10^-19 C)

Using the above equation, we can find the number of electrons that flow through the wire.

Final Answer:
The number of electrons flowing through the wire can be calculated as:

N = 2.25 x 10^21 electrons

Therefore, approximately 2.25 x 10^21 electrons would flow through the wire.