Number of electrons present in the species H₂⁺, He, H₂ and O₂⁺ respectively are:

The correct answer is Option 1.

Key Points

• The number of electrons in a species is determined by the atomic number of the element and its charge (if it is an ion).
• For H₂⁺, the molecule has lost one electron, leaving it with 1 electron.
• Helium (He) is a neutral atom with an atomic number of 2, so it has 2 electrons.
• For H₂, each hydrogen atom contributes 1 electron, making a total of 2 electrons.
• O₂⁺ is an ion where one electron has been removed from the neutral O₂ molecule (16 electrons in total), leaving it with 15 electrons.

Additional Information

• Electron Counting in Ions:
  • In a positively charged ion, electrons are subtracted from the neutral atom’s count.
  • For a negatively charged ion, electrons are added to the neutral atom’s count.
• Atomic Number:
  • The atomic number of an element represents the number of protons in its nucleus.
  • In a neutral atom, the number of protons equals the number of electrons.
• Molecular Electron Count:
  • For diatomic molecules like H₂ and O₂, the total number of electrons is the sum of the electrons from each atom.
  • For charged molecules (e.g., H₂⁺ or O₂⁺), adjust the electron count based on the charge.
• General Case:
  • H₂⁺: 2 electrons in H₂ minus 1 (due to the +1 charge) = 1 electron.
  • He: Atomic number 2 = 2 electrons (neutral atom).
  • H₂: 1 electron from each H atom = 2 electrons (neutral molecule).
  • O₂⁺: 16 electrons in O₂ minus 1 (due to the +1 charge) = 15 electrons.