Final answer:
An element with an electron configuration of 1s²2s²2p⁶3s² is in Group 2 of the periodic table. To be in the same group, another element must have a valence electron configuration that ends in 3s². Thus, the element with the configuration 1s²2s²2p⁶3s² would be in the same group.
Step-by-step explanation:
The electron configuration of 1s²2s²2p⁶3s² indicates an element in Group 2 (the alkaline earth metals) of the periodic table, because the outermost shell (valence shell) has two electrons. To identify an element in the same group, we need to look for a similar outer-shell electron configuration.
- 1s²2s²2p⁶3s²3p⁶ - This configuration shows a full outer shell and belongs to Group 18, the noble gases.
- 1s²2s²2p⁶3s² - This configuration has two valence electrons in the 3s sublevel, same as our original element, and thus would be in the same group.
- 1s²2s²2p⁶3s²3p⁶4s² - An element with this configuration has a full 3p sublevel and additional electrons in the 4s sublevel, placing it in Group 2, but in a different period.
- 1s²2s²2p⁶3s¹ - This configuration, with only one valence electron, would be found in Group 1, the alkali metals.
Therefore, the element with an electron configuration of 1s²2s²2p⁶3s± will be in the same group as the original element because they share the same number of valence electrons.