n = 3
A d subshell has a secondary quantum number, l = 2.
The allowed values for l are 0, 1, 2, 3, … n – 1.
We can write this mathematically as
l ≤ n – 1 Add 1 to each side
l +1 ≤ n Reverse the inequality
n ≥ l + 1
Thus, if l = 2, n ≥ 3
Thus, the lowest energy level where you can find a d subshell is n = 3.
Answer : The lowest numbered energy level where a 'd' sublevel is found is 3.
Explanation : According to the theory of order of electron filling;
The 4s orbitals is observed to have a lower energy than the 3d, and so the 4s orbitals are filled first.
It is known that 4s electrons are lost first during ionisation activity. Therefore, the electrons lost first will come from the highest energy level, furthest from the influence of the nucleus.
So, the lowest energy level where 'd' sub shell will be found is 3d.
the grams of barium that are in 2.3 x 10^23 atoms of barium is 52.4 g (answer c)
mass = moles of ba x molar mass of ba
molar mass of ba from periodic table= 137.3 g/mol
use the avogadro's law constant to calculate the moles of barium
that is 1 mole = 6.02 x 10^23 atoms
? moles = 2.3 x 10^23 atoms
by cross multiplication
=(1 mole x 2.3x 10^23 atoms) / 6.02 x10^23 atoms)= 0.382 moles
mass is therefore = 137.3 g/mol x 0.382 mol = 52.4 ( answer c)