In the context of the periodic table, the elements that belong to Group 2 are the alkaline earth metals. These include:
- Beryllium (Be, atomic number 4)
- Magnesium (Mg, atomic number 12)
- Calcium (Ca, atomic number 20)
- Strontium (Sr, atomic number 38)
- Barium (Ba, atomic number 56)
- Radium (Ra, atomic number 88)
In the notation you've provided (3A, 8B, 12C, 19E), if these refer to groups or classifications of elements rather than their actual atomic numbers, I would need more context to determine which specific elements you're referencing and whether any of them belong to Group 2.
Please clarify what A, B, C, and E represent in your question, and I would be happy to help!