What is 1s2 2s2 2p5 ?

Answer:

1s2 2s2 2p5 means that

●s subshell of first orbit or energy level has two electrons,

●s subshell of second orbit or energy level has two electrons,

●p subshell of second orbit or energy level has five electrons,

From 1s2 2s2 2p5 electron configuration,we get 2+2+5 = 9 electrons.

We know that electron's number is equal to proton number or atomic number for neutral atom.

Since here there is no words about charge,we can say that 1s2 2s2 2p5 indicates the element whose atomic number is 9.

Now if you look at the periodic table,F (Fluorine) has atomic number 9.

So 1s2 2s2 2p5 is the electron configuration of F (Fluorine).