Answer:
Xenon
Explanation:
The core electrons of an element are the electrons that do not take part in the chemical reactions of the element
The electronic configuration of barium Ba is presented as follows;
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s²
2+2+6+2+6+2+10+6+2+10+6
The valence electrons of boron are the 6s² electrons
The core electrons of boron are the; 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶
The electronic configuration of xenon, Xe, which is the previous noble element before barium, is presented as follows;
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ which is the same as the core electrons of barium
Therefore, the total number of electrons in xenon is equal to the number of core electrons in barium
