Question

1.	How many different 4s states does the hydrogen atom have?
	10 2 0 8
2.	The element boron has the atomic number Z = 5. What element of the next-larger Z has properties similar to those of boron?
	neon aluminum carbon beryllium

3.	How many 3d electrons can an atom have?
	10 0 8 4 6
4.	What is the atomic number Z of the element with the electron configuration 1s22s22p63s23p63d4s2?
	21 18 9 4

Answer 1

1)

atomic number of hydrogen is 1 so no 4s state exit

answer = 0        <------answer

2)

aluminium    <------answer

both are belong to same group and same number of valency
electrons present in their valency shells these valeny

electrons are responsible for similar properties

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3)

10      <------answer

because d subshell contain 5 orbitals. each orbital can acccomidate 2 electrons , so 5 orbital an accomidate 10 electrons

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4)

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹ 4s²

2 + 2 +6 + 2 +6 + 1 +2 = 21    <------answer