4. which of the following is a pseudo-noble-gas electron configuration?
o a 1s22s22p3s23p%3d10
ob 1s22s22p63s23p6
oc 1s22s22p63s2305
od 1s22s²2p63s23d10452

1s2 2s2 2p6 3s2 3d5  is a pseudo-noble-gas electron configuration

Explanation:

It is the technetium with atomic number 43. Being the lightest element having isotopes with all radioactive and no one are more stable as compared to that of technetium which is in fully ionised state i.e. 97 Tc. This element is mostly used for gamma ray emission in medical treatment. Also found to be used as corrosion inhibitor in case of steel, when present in small amount gives better result. This metal is silver grey colour that is found to discoloration when comes in contact with moist air. Its isotopes are radioactive.

1s2 2s2 2p6 3s2 3p6 3d10

Explanation:

A pseduo noble gas configuration refers to charged species with electron configurations that are almost identical to that of one of the noble gases.

The noble gas (n-1)d^10 (where n refers to the principal quantum number of the outer s orbital) configuration of ions is commonly known as a pseudo noble gas configuration. The configuration stated in the answer is for Cu^+ ion. n in the case of Cu^+ ion is 4(since copper metal has a 4s1 level).

Note that; 1s2 2s2 2p6 3s2 3p6 is the electron configuration for argon, followed by 3d^10. Hence our definition for a pseudo noble gas.