Question

The ion of an element has 3 positive charges. Mass number of the atom is 27 and the number of neutrons is 14. What is the number of electrons in the ion ?

• A. 13
• B. 10
• C. 14
• D. 16

Hint:

1. Find protons: Protons = Mass Number - Neutrons = \(27 - 14 = 13\) protons. 2. In a neutral atom, electrons = protons = 13 electrons. 3. Ion has +3 charge: This means it has LOST 3 electrons. 4. Electrons in ion = Electrons in neutral atom - 3 = \(13 - 3 = 10\) electrons.

Answer 1

The Correct Option is B

Concept:
Mass Number (\(A\)) = Number of protons (\(p\)) + Number of neutrons (\(n\)).
Atomic Number (\(Z\)) = Number of protons (\(p\)). For a neutral atom, \(Z\) also equals the number of electrons.
For an ion, the number of electrons changes. A positive charge means electrons are lost. A negative charge means electrons are gained. Step 1: Given information
Charge of the ion = +3 (3 positive charges).
Mass number of the atom (\(A\)) = 27.
Number of neutrons (\(n\)) = 14. We need to find the number of electrons in the ion. Step 2: Find the number of protons (\(p\)) We know \(A = p + n\). So, \(p = A - n\). \(p = 27 - 14 = 13\). The number of protons in the atom (and also in the ion, as protons don't change when an ion forms) is 13. This means the atomic number (\(Z\)) of the element is 13. (This element is Aluminium, Al). Step 3: Determine the number of electrons in the neutral atom For a neutral atom, the number of electrons is equal to the number of protons. Number of electrons in a neutral atom = 13. Step 4: Determine the number of electrons in the ion The ion has 3 positive charges (+3). A positive charge indicates that the atom has lost electrons. A +3 charge means the atom has lost 3 electrons. Number of electrons in the ion = Number of electrons in neutral atom - Number of electrons lost Number of electrons in the ion = \(13 - 3 = 10\). Therefore, the number of electrons in the ion is 10. This matches option (2).