Question !
Calculate the radius of first orbit of He+ atom .
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Answers
Answer:
0.2645Å
Explanation:
To calculated the radius of First orbit of Helium (He+)
We know that ,in He+
n = 1 and z = 2
Also , bohrs radius is given by the formula , (R’)(n^2)/Z
Rydbergs constant = R’(R= 0.529Å)
=> R = R’/2
=> Radius = 0.529Å/2
=> Radius = 0.2645Å
Answer:
estion
Answers
Related Questions
Correct order of radius of the 1st orbit of H, He+, Li2+ and Be3+ is:
(A)- H>He+>Li2+>Be3+
(B)- Be3+>Li2+>He+>H
(C)- He+>Be3+>Li2+>H
(D)- He+>H>Li2+>Be3+
Answer
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Hint: From the Bohr’s model of hydrogen atom, the expression for radius of the nthorbit of the hydrogen atom is given as
r=aon2
ao is the radius of the first orbit of the hydrogen atom and is equal to 52.9 pm.
For H-like particles, radius of the nthorbit is given by the expression
r=aon2Z
Complete answer:
He+, Li2+ and Be3+contain one electron like hydrogen, so they are called H-like particles.
Radius of the first orbit of the hydrogen atom is called Bohr's radius, i.e. ao=52.9pm.
The expression for the radius of nth orbit for H-like particles is given as
r=aon2Z
Where, Z is the atomic number of H-like particles.
We have to find the order of the radius of the 1st orbit, i.e. n = 1.
Now, the radius of the first orbit for He+, Li2+ and Be3+ becomes
r=aoZ
Since, the value of ao is constant, i.e. 52.9 pm, therefore, we can say that radius r is inversely proportional to the atomic number Z of the H-like particle, i.e.
r∝1Z
Atomic number, Z for He+, Li3+ and Be3+ is 2, 3 and 4, respectively.
Since, atomic number Z increases from H to Be3+, radius r being inversely proportional decreases from Be3+ to H. This implies that the radius of the first orbit is largest for H and smallest for Be3+.
Therefore, the correct order of radius of the 1st orbit of H, He+, Li2+ and Be3+ is:
H>He+>Li2+>Be3+
Explanation: