Final answer:
Selenium has one electron in its outer shell of electrons, while electron arrangements in atoms are influenced by shielding and the periodic table layout.
Explanation:
Selenium has only one electron in its outer shell of electrons, with the electron configuration being 1s² 2s²p 3s²p6d¹0 4s²p4.
In multielectron atoms, the net force on electrons in the outer shells is reduced due to shielding, making the electron arrangement significant.
The elements within a particular row on the periodic table have increasing numbers of electrons as the columns proceed from left to right, with not all shells being completely filled.
Learn more about Electron Configurations and the Periodic Table here:
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