If an element forms an ion with a charge of −2, what does this indicate about its valency?

Question

Examoogle · Accepted Answer

The correct answer is Option B: The element has gained 2 electrons.. An ion with a charge of $-2$ (an anion) indicates that the neutral atom has gained two extra electrons. Since electrons are negatively charged particles, adding them to the neutral atom results in a net negative charge of $-2$.

Step-by-Step Solution & Concepts:
An ion with a charge of $-2$ (an anion) indicates that the neutral atom has gained two extra electrons. Since electrons are negatively charged particles, adding them to the neutral atom results in a net negative charge of $-2$.

Working Principle: Atoms are electrically neutral because the number of protons equals the number of electrons. When an atom gains electrons to achieve a stable noble gas configuration (octet rule), the number of electrons exceeds the number of protons by the amount of the charge. The net charge $Q$ is calculated as $Q = (	ext{Number of protons}) - (	ext{Number of electrons})$. For an ion with a $-2$ charge, $Q = Z - (Z + 2) = -2$.

Key Formulas: $Q = N_p - N_e$ — The net charge is the difference between the number of protons and electrons.; $	ext{Charge} = -n 	imes e^-$ — Gain of $n$ electrons results in a $-n$ charge.

Key Points: Anions are negatively charged ions formed by the gain of electrons.; Cations are positively charged ions formed by the loss of electrons.; The valence shell configuration determines an element's ability to gain or lose electrons.; Non-metals typically gain electrons to form negative ions.

Advantages: Predicting chemical reactivity.; Understanding ionic bond formation.

Applications: Formation of oxide ions ($O^{2-}$) in metal oxides.; Formation of sulfide ions ($S^{2-}$) in ionic compounds.

Additional Info: The valency of an element is the combining capacity, which is equal to the number of electrons gained or lost to complete the octet.. Option A is incorrect because losing electrons results in a positive charge (cation). Option C is impossible as electrons do not reside in the nucleus. Option D is incorrect because changing the number of protons would change the identity of the element itself (transmutation).

Answer: B is correct — An ion with a $-2$ charge is formed when a neutral atom gains 2 electrons, as electrons carry a negative charge.

Exam Tip: Always remember: Loss of electrons makes the atom positive (Oxidation), and Gain of electrons makes the atom negative (Reduction).

Examoogle · Answer

Option A: The element has lost 2 electrons.

Examoogle · Answer

Option C: The element has 2 electrons in the nucleus.

Examoogle · Answer

Option D: The element has gained 2 protons.

Correct Answer

Solve 10,000+ More Questions with AI Tutor

Discussion (0)

Correct Answer

Solve 10,000+ More Questions with AI Tutor

Related Questions

Discussion (0)