21. Write the noble gas abbreviated e configuration for the following: ex.)[Ne]3s^2. __ In __ Ba __

To write the noble gas abbreviated electron configuration for barium (Ba), we need to follow these steps:<br /><br />1. Identify the nearest preceding noble gas to barium.<br />2. Write the electron configuration for barium starting from the noble gas core.<br /><br />Barium (Ba) has an atomic number of 56. The nearest preceding noble gas is xenon (Xe), which has an atomic number of 54.<br /><br />The electron configuration for xenon is:<br />\[ \text{[Xe]} = 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^6 \]<br /><br />Now, we add the remaining electrons to reach barium's total of 56 electrons:<br />- After xenon, we have 2 electrons in the 6s orbital.<br /><br />So, the noble gas abbreviated electron configuration for barium (Ba) is:<br />\[ \text{[Xe]} 6s^2 \]<br /><br />Therefore, the noble gas abbreviated electron configuration for barium (Ba) is:<br />\[ \text{[Xe]} 6s^2 \]