Elements 36 and 54 have similar chemical properties. based on their electronic configurations, predict the atomic number of a heavier element that should also share these chemical properties. express your answer as an integer.

86  

Explanation:

The electron configuration of element 36 is

1s² 2s²2p⁶ 3s²3p⁶ 4s²3d¹⁰4p⁶

Now, we add 18 electrons to reach element 54. Its electron configuration is

1s² 2s²2p⁶ 3s²3p⁶ 4s²3d¹⁰4p⁶ 5s²4d¹⁰5p⁶

These elements have similar properties because their electron configurations end in p⁶.

To reach the next element with similar properties, we must add enough electrons to reach a p⁶ configuration.

We follow the Wiswesser diagram below to determine the sequence order of the subshells.

To reach a p⁶ configuration, we must add 32 electrons, because we must fill the 4f orbitals.

The electron configuration of the next element with similar properties is  

1s² 2s²2p⁶ 3s²3p⁶ 4s²3d¹⁰4p⁶ 5s²4d¹⁰5p⁶ 6s²5d¹⁰4f¹⁴6p⁶

And the element number is 54 + 32 = 86.  

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