All nuclei with Z > 83 are radioactive, but up to Z = 92 the half-lives are sufficiently long that they are still present in the crust of the earth. Uranium with Z = 92 has the largest atomic number of the naturally occuring elements. The elements with Z > 92 have been been produced in the laboratory by fusing together lighter nuclei or in nuclear reactors by absorbing neutrons. The most common type of smoke detector uses a small amount of Americium (Z = 95). Elements up to Z = 118 have been produced, but with great difficulty.

The quest for heavier elements continues, and there is a prediction that for Z > 112, some nuclei will be long lived with half lives of the order of a year. What superheavy element is the next noble gas after radon (Z = 86)? The figure below provides a useful mnemonic for the order in which the electronic energy levels are filled as we progress to higher Z atoms.

Use the figure to see the configurations of the known noble gases. Then make an extrapolation to the next noble gas. Find the atomic number of the next noble gas, and find its electron configuration. With the exception of helium, a noble gas occurs when a p level is filled.

For the next noble gas Z = .

In this heavy noble gas atom:

The number of 1s electrons is    
The number of 2s electrons is    
The number of 2p electrons is    
The number of 3s electrons is    
The number of 3p electrons is    
The number of 4s electrons is    
The number of 3d electrons is    
The number of 4p electrons is    
The number of 5s electrons is    
The number of 4d electrons is    
The number of 5p electrons is    
The number of 6s electrons is    
The number of 4f electrons is    
The number of 5d electrons is    
The number of 6p electrons is    
The number of 7s electrons is    
The number of 5f electrons is    
The number of 6d electrons is    
The number of 7p electrons is    
The number of 8s electrons is

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