which of the following correctly matches the ion with the total number of electrons in the ion? a. br -, 34 electrons. mg2+, 14 electrons. zn2+, 28 electrons. p3-, 15 electrons. h+, 2 electrons
Answers
Answer:
A. According to Bohr's theory, the energy of electron in n
th
Bohr's orbit of H-atom or hydrogen-like atoms/ions is given by:
E
n
=−R
H
n
2
Z
2
where R
H
=2.18×10
−18
J and Z=atomic number, n=n
th
orbit
Thus, E
n
=−2.18×10
−18
n
2
Z
2
J
B. Energy gap between two Bohr orbits n
1
and n
2
is given by
ΔE=E
2
−E
1
and using E
n
=−R
H
n
2
Z
2
ΔE=E
2
−E
1
=−R
H
n
2
2
Z
2
−(−R
H
n
1
2
Z
2
)
ΔE=R
H
Z
2
(
n
1
2
1
−
n
2
2
1
)
for hydrogen atom Z=1
thus ΔE=R
H
(
n
1
2
1
−
n
2
2
1
)
C. In photoelectric effect, a given metal has characteristic threshold frequency (ν
0
) for photoelectric effect that is required for ejection of electron. Threshold energy is called the work function (hν
0
) of the metal and the excess of energy gets converted to the kinetic energy of the photoelectron.
since total energy is conserved:
Energy given=work function + KE
hv=hv
0
+
2
1
mv
2
where, h=6.626×10
−34
Js
D. Energy of a photon associated with frequency ν is given by:
E=hν=
λ
hc
Thus energy of one mole of photons= N
A
× energy of one photon
where N
A
=avogadro's constant=6.022×10
−23
mol
−1
E=N
A
hν=N
A
λ
hc