* Isoelectronic means having the same number of electrons.

* Helium (He) has 2 electrons.

Therefore, any atom or ion that also has 2 electrons will be isoelectronic with helium. Here are a few examples:

* Hydrogen anion (H-): Hydrogen has 1 proton and 1 electron. Gaining an electron gives it 2, making it isoelectronic with helium.

* Lithium cation (Li+): Lithium has 3 protons and 3 electrons. Losing an electron gives it 2, making it isoelectronic with helium.

* Beryllium dication (Be2+): Beryllium has 4 protons and 4 electrons. Losing 2 electrons gives it 2, making it isoelectronic with helium.

Important Note: The number of protons (atomic number) determines the element. While these ions are isoelectronic with helium, they are still different elements due to their differing numbers of protons.