which element belongs to this group, although it has only two electrons?
Helium is in the noble gas group because its outer shell is full despite having only two electrons. Therefore like the rest of that column it does not react with much of anything.
The group you are referring to is Group 18, also known as the noble gases. Noble gases have a full outer electron shell and are generally unreactive. However, there is an exception to this trend in Group 18 - helium (He). Despite having only two electrons, which would generally place it in Group 2, helium is placed in Group 18 due to its similar electronic configuration to the other noble gases.
The element that belongs to a group and has only two electrons is helium (He). Helium is found in the top-right corner of the periodic table in Group 18, also known as the noble gases.
To determine this, you could start by counting the number of electrons in each shell of the atom. The first shell can hold a maximum of 2 electrons, the second shell can hold a maximum of 8 electrons, and so on. The group number indicates the number of valence electrons, which are the electrons in the outermost shell.
In the case of helium, it is located in Group 18, which means it has 8 valence electrons. However, the first shell (also called the K-shell) can only hold 2 electrons, so helium only has 2 electrons in total. This makes it an exception among the noble gases, as all the other elements in the group have 8 valence electrons.
So, helium, despite having only two electrons, belongs to Group 18 or the noble gases.