Question 16 of 42beginner💡 UnderstandShort Answer2 marks

Helium contains two protons in its nucleus and two electrons. In which way will the two electrons be arranged in its atomic shell?

Correct Answer

The two electrons in a helium atom will be arranged in the K-shell. Electrons are filled in a stepwise manner, starting from the shell closest to the nucleus. The maximum number of electrons that can be accommodated in the K-shell (n=1) is given by the formula 2n², which equals 2. Since helium has only two electrons, both will occupy the K-shell, completely filling it.

Exercise: QUESTIONS | Q: 2 | (Page 12)
For More Understanding

Explanation

The textbook explains that electrons fill shells starting from the one closest to the nucleus. For the K-shell (n=1), the maximum electron capacity is calculated using the Bohr-Bury formula 2n², which yields 2. Since helium has exactly 2 electrons, both will be placed in the first and innermost K-shell, thus completing it.

Solution Steps

  1. Step 1: Identify the number of electrons in helium, which is 2.

  2. Step 2: Determine the order of filling shells, which starts from the innermost K-shell.

  3. Step 3: Calculate the maximum capacity of the K-shell using the formula 2n² (2 x 1² = 2).

  4. Step 4: Conclude that both electrons will be arranged in the K-shell, as it can hold a maximum of 2 electrons.

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