Select all the true statements. when an atom gains an electron, it becomes a cation. anions carry a positive charge. the cl− and br− ions have the same number of electrons. the k+ ion is formed when a potassium atom loses one electron. the fe2+ and fe3+ ions have the same number of protons. the cu+ and cu2+ ions have the same number of electrons.

The statements 4 and 5 are true.

Explanation:

1. When an atom gains an electron it becomes negatively charged. This negatively charged species is called anion.

A + e⁻ →  A⁻ (anion)

Therefore, the statement 1 is false.

2.  An anion is formed when an atom gains an electron and becomes negatively charged. Therefore, an anion is a negatively charged species.

A + e⁻ →  A⁻ (anion)

Therefore, the statement 2 is false.

3. The atomic number of chlorine atom Cl is 17 and atomic number of bromine atom Br is 35.

Since, for neutral atom, the atomic number of an atom is equal to the number of electrons present in that atom.

Therefore, the number of electrons in Cl atom is 17 and the number of electrons in Br atom is 35.

When the Cl atom gains one electron it forms Cl⁻ ion and when the Br atom gains one electron it forms Br⁻ ion.

Therefore, the number of electrons in Cl⁻ ion is 17 + 1 = 18 electrons

and the number of electrons in Br⁻ ion is 35 + 1 = 36 electrons

Therefore, Cl⁻ and Br⁻ ions do not have the same number of electrons.

Therefore, the statement 3 is false.

4. When potassium atom (K) loses one electron it forms a positively charged species called potassium cation (K⁺).

K  → K⁺ + e⁻

Therefore, the statement 4 is true.

5. The atomic number of Fe atom is 26.

Since, the atomic number of an atom is equal to the number of protons present in that atom.

When the Fe atom loses two electrons to form Fe²⁺ and when the Fe atom loses three electrons to form Fe³⁺ ion, the number of protons remains the same.

Therefore, the ions Fe²⁺ and Fe³⁺ have the same number of protons.

Therefore, the statement 5 is true.

6. The atomic number of copper atom Cu is 29.

Since, for neutral atom, the atomic number of an atom is equal to the number of electrons present in that atom.

Therefore, the number of electrons in Cu atom is 29

When the Cu atom loses one electron it forms Cu⁺ ion and when the Cu atom loses two electrons it forms Cu²⁺ ion.

Cu  → Cu⁺ + e⁻                and    Cu  → Cu²⁺ + 2e⁻

Therefore, the number of electrons in Cu⁺ ion is 29 - 1 = 28 electrons

and the number of electrons in Cu²⁺ ion is 29 - 2 = 27 electrons

Therefore,  Cu⁺ ion and Cu²⁺ ion do not have the same number of electrons.

Therefore, the statement 6 is false.

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