Ion charge from electron count in cobalt

Steps:

• Cobalt's atomic number is 27, so neutral atoms have 27 protons and 27 electrons.
• This particle has 24 electrons, indicating loss of 3 electrons from neutral cobalt.
• Loss of electrons creates a positive ion with charge equal to electrons lost: 3+.
• Nucleon number 60 confirms it's cobalt-60 isotope, but charge depends on electrons.

Why A is correct:

• Ion charge = protons - electrons = 27 - 24 = +3, defining a 3+ ion per atomic structure rules.

Why the others are wrong:

• B: Electron loss results in positive charge, not negative (anions gain electrons).
• C: Protons define the element; cobalt always has 27 protons, not 24.
• D: Neutrons = nucleon number - protons = 60 - 27 = 33, not 24.

Final answer: A