What element is represented by the electron configuration [Ar] 4s^2 3d^10 4p^4?

The given electron configuration [Ar] 4s^2 3d^10 4p^4 corresponds to the element Selenium. To understand why this is the case, it's important to break down the electron configuration.

In this notation, [Ar] represents the core electrons of Argon, which accounts for the first 18 electrons. After Argon, there are 2 electrons in the 4s subshell, 10 electrons in the 3d subshell, and finally, 4 electrons in the 4p subshell.

Adding these up gives a total of 18 (from Argon) + 2 (from 4s) + 10 (from 3d) + 4 (from 4p) = 34 electrons. The atomic number, which indicates the number of protons in the nucleus and, for neutral atoms, the number of electrons, reveals that the element with 34 electrons is Selenium.

This comprehensive understanding of how to interpret the electron configuration is essential for identifying elements based on their electron arrangements. It highlights the arrangement of electrons in different energy levels and subshells, leading to the identification of Selenium in this case.