Question #e453d

1 Answer
Jan 3, 2017

Answer:

The arrangement of electrons in the orbitals of an atom or molecule.

Explanation:

So basically the electronic configuration tells us which element is present in which groups, in which periods and in which block (s block, p block, d block and f block).

By knowing how many electrons are present in the shells, we can find the place of an element in the periodic table.

Q: Find the electronic configuration of aluminium?

Ans: #"Al"# has an atomic number equal to #13#

So,

#(1s^2)/"K" " " (2s^2,2p^6)/"L"" "(3s^2,3p^1)/"M"#

Here #"K#" is the first shell, #"L"# is the second, and #"M"# is the third shell (the valence shell).

As #n = 3#, #"Al"# is present in the #"3rd"# period. Since the total number of electrons in the valence sub-shells are

#2+1=3#

it must be present in group lllA (in Roman Numerals). or group 13. and in the last shell, we have a #"p"# so we can say that aluminium is present in the p block.

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