Ka for weak acids is ---> Ka= (X)²/ (initial- X)
initial= 0.0400 M
to find X, you can find the H concentration using pH
[H+]= 10^-pH
[H+]= 10^-1.80= 0.016 which is X
ka = (0.016)²/ (0.0400 - 0.016) = 0.011
The top of a wave is called the wave crest.
Can you take a screen shot im kind of lost on this
So boron has an electronic configuration of 1S2 2S2 2P1 and the element with an atomic number of 3 is Lithium which has an electronic configuration of 1S2 2S1.
So the answer is 1S2 2S1.