Question

Give the symbol and name for the ion with 34 protons and 36 electrons?
• \( \mathrm{Al^{3+}} \)
• \( \mathrm{Se^{2-}} \)
• \( \mathrm{Te^{2-}} \)
• \( \mathrm{Mg^{2+}} \)

• A. \( \mathrm{Al^{3+}} \)
• B. \( \mathrm{Se^{2-}} \)
• C. \( \mathrm{Te^{2-}} \)
• D. \( \mathrm{Mg^{2+}} \)

Hint:

To identify ions quickly: \[ \text{Atomic Number} = \text{Number of Protons} \] Then compare electrons and protons:
• More electrons \(\Rightarrow\) negative ion
• Fewer electrons \(\Rightarrow\) positive ion

Answer 1

The Correct Option is B

Concept: The number of protons in an atom determines its atomic number and hence its identity. Important facts:
• Number of protons \(=\) atomic number
• Neutral atom: \[ \text{Number of protons} = \text{Number of electrons} \]
• If electrons are more than protons, the ion is negatively charged.
• If electrons are less than protons, the ion is positively charged. Charge on ion is calculated as: \[ \text{Charge} = \text{Protons} - \text{Electrons} \]

Step 1: Identify the element using the number of protons. The ion contains: \[ 34 \text{ protons} \] Atomic number \(34\) corresponds to the element Selenium. Thus, the element is: \[ \mathrm{Se} \]

Step 2: Determine the charge on the ion. The ion has: \[ 36 \text{ electrons} \] Number of protons: \[ 34 \] Since electrons are greater than protons: \[ 36 - 34 = 2 \] The ion has gained \(2\) extra electrons. Therefore, the charge on the ion is: \[ 2- \] Hence, the ion is: \[ \mathrm{Se^{2-}} \]

Step 3: Verify the remaining options.
• \( \mathrm{Al^{3+}} \): Aluminium has atomic number \(13\), not \(34\).
• \( \mathrm{Te^{2-}} \): Tellurium has atomic number \(52\).
• \( \mathrm{Mg^{2+}} \): Magnesium has atomic number \(12\). Thus, only Selenium matches the required proton number. Final Conclusion: The ion having \(34\) protons and \(36\) electrons is: \[ \boxed{\mathrm{Se^{2-}}} \] This ion is called: \[ \boxed{\text{Selenide ion}} \] Hence, the correct answer is: \[ \boxed{(2)} \]