Question

An clement which can cxist as a positive ion in acid solution and also as ve ion in basic solution is called (1) Amphoteric (2) \Lambdacidic (3) Basic (4) Neutral

Short answer

The correct answer is (1): Amphoteric.

Step-by-step solution

Understand the Definition

An element that can act as both a positive ion in acidic solution and as a negative ion in basic solution has the property of being amphoteric.

Review the Options

The options provided are: amphoteric, \(\text{Lambdacidic}\), basic, and neutral. \(\text{Amphoteric}\) substances can act both as acids and bases depending on the environmental conditions.

Match the Definition to the Options

Compare the given definition to the options. The correct term for an element that can exist both as a positive ion in acid solution and as a negative ion in basic solution is 'amphoteric'.

Conclusion

Thus, the correct answer based on the given definition is option (1): Amphoteric.

Key concepts

Positive Ion

A positive ion, also known as a cation, forms when an atom loses one or more electrons. This loss leaves the atom with a net positive charge due to an excess of protons over electrons.
An important example of cation formation happens in acidic solutions.
Acids donate protons (H⁺ ions) to other substances, often causing those substances to lose electrons and form cations.

Acidic Solution

An acidic solution is characterized by an excess of hydrogen ions (H⁺). This occurs when an acid dissolves in water, releasing H⁺ ions.
These solutions have a pH value of less than 7.
Typical properties include: a sour taste, the ability to conduct electricity, and turning blue litmus paper red.

Basic Solution

A basic solution, or alkaline solution, has more hydroxide ions (OH⁻) compared to hydrogen ions (H⁺). This results in a pH value greater than 7.
Bases are substances that accept protons (H⁺) or donate electron pairs during reactions.
Common characteristics include: a bitter taste, slippery feel, and turning red litmus paper blue.
When certain elements or compounds can exist as negative ions in such solutions, they might be amphoteric.

Negative Ion

A negative ion, known as an anion, forms when an atom gains one or more electrons, giving it a net negative charge due to an excess of electrons over protons.
Anions are common in basic solutions where substances accept protons (H⁺ ions), often leading to the addition of electrons.
Examples include: chloride ion (Cl⁻), sulfate ion (SO₄²⁻), and phosphate ion (PO₄³⁻).
The ability to form anions in a basic solution is a key property of amphoteric substances.