atomic number

Question 1

The velocity of photon is

Answer 1

Independent of its wavelength
Because the photons move with the speed of light so their velocity is independent of wavelength

Question 2

The 3rd orbit of hydrogen atom is______ away from the nucleus as compare to first orbit

Answer 2

Distance of shell from nucleus given by 0.529n2Ao
1st shell ⟶ 0.529(1)2Ao = 0.529 Ao
3rd shell ⟶ 0.529(3)2Ao = 0.529 × 9 Ao
so, 9 times away than 1st shell

Question 3

what is meant by isoelectronic

Answer 3

both ions/atom have the same no. of electrons

Question 4

Which of the following quantum numbers describes energy of an electron in an atom?

Answer 4

Principal quantum number (n) provides information about the energy of the an electron in an atom.
It is also present in energy formula derived by Bohr.
E = 2.178 × 10-18 × [1/n2] J

Question 5

formula for calculating radial nodes

Answer 5

Radial nodes = n – l – 1
for 4f orbital 4 – 3 – 1 = 0

Question 6

Angular momentum of 2nd orbit is

Answer 6

Angular momentum is given by nh/2π. Since n=2 so it becomes h/π

Question 7

With increase in value of principle quantum number ‘n’, the shape of ‘s’ orbital remains same although their sizes

Answer 7

n α size of ‘s’ orbital
so sizes increas

Question 8

The charge of one gram of electron is

Answer 8

One electron mass is 9.109⨯10-28 g, so there are 1/(9.11⨯10-28) = 1.098⨯1027 electrons per gram. One electron charge is 1.602⨯10-19 C, so the charge of a gram of electrons is
(1.098⨯1027) (1.602⨯10-19) C = 1.759⨯108 C.
USEFUL TRICK: In the actual test use approximations to save time.
Mass of electron is 9⨯10-28 g so there are 1/(9⨯10-28) = 1⨯1027 electrons per gram. Multiple it with charge to get 1.6⨯108 C and the closest choice to this approximation is C.

Question 9

Maximum number of electrons in an orbital of f-sub shell are

Answer 9

Orbital of any sub-shell can accommodate 2e– Only.

Question 10

Which quantum number tells about the orientation of orbitals?

Answer 10

The magnetic quantum number determines the number of orbitals and their orientation within a subshell. Consequently, its value depends on the orbital angular momentum quantum number l. Given a certain l, ml is an interval ranging from –l to +l, so it can be zero, a negative integer, or a positive integer.

Question 11

Which of the following quantum numbers determines number of orbitals in a sub-shell

Answer 11

Magnetic quantum number
The value of “m” gives us information of degeneracy of orbitals in space. The different values of ‘m’ represent total number of different space orientations for a sub-shell.

Question 12

The atomic number of an element is 17. The number of orbits is?

Answer 12

3
the number of orbitals containing eclectrons in the valence shell is 3
as 3s2 and 3p5

Question 13

For a given value of “l”, the total values of “m” are

Answer 13

(2l + 1)

Question 14

The total number of electrons in a sub-shell can be determined by

Answer 14

2(2l + 1)

Question 15

The number of orbitals in the fourth energy level is

Answer 15

16
n2

Question 16

In a Multi-electron atoms, the energy of the electrons in a particular orbital is determined by

Answer 16

n + l

Question 17

The divisibility of atom was showed by

Answer 17

JJ Thomson suggested that atoms are divisible and consist of negatively charged particles.

Question 18

Angle of deflection in magnetic field was studied by

Answer 18

J. Perrin
1895

Question 19

Charge of electron was measured by

Answer 19

Millikan

Question 20

Who modified Bohr’s theory by introducing elliptical orbital for electron path

Answer 20

Sommerfield

Question 21

the maximum possible number of electrons a shell n can accomadate by

Answer 21

2n squared

Question 22

JJ thomson determined the

Answer 22

e/m value of electron

Question 23

rls between n and L is?

Answer 23

L = n - 1

Question 24

diameter of an atom

Answer 24

0.5 nm

Question 25

value of rydberg constant

Answer 25

1.09678 x 10’ 7 m-1

Question 26

in gases how many times is the distance greater than their diameters

Answer 26

300

Question 27

the radius of an electron orbit in a hydrogen atom is of the order of

Answer 27

1 x 10 11th power meters
0.53 Armstrong

Question 28

the mass of one mole of electrons is

Answer 28

0.54 mg

Question 29

shielding effect is also called

Answer 29

screening effect

Question 30

the number of atoms present in a molecule determines it’s

Answer 30

atomicity

Question 31

how many times are hb molecules heavier than H atoms?

Answer 31

68,000

Question 32

which of the following technique is used to measure the atomic radius

Answer 32

x ray anaylsis

Question 33

magnetic quantum number of s is

Answer 33

zero

Question 34

the presence of several fine lines in a line spectrum shows the presence of?

Answer 34

sub shells

Question 35

which character of p-orbital determines the geometry of molecules

Answer 35

directional

Question 36

the value of the principal quantum number n represent?

Answer 36

shells or energy levels

Question 37

canal rays are produced in te discharge tube from

Answer 37

gas molecules in the tube

Question 38

which experiment proved electron’s particle nature

Answer 38

paddlewheel/pinwheel

Question 39

after 3d is filled next electron goes 4p according to

Answer 39

auf ba’s principle

Question 40

electrons w same “m” quantum number prefered to be — according to —

Answer 40

Unpaired
Hund’s rule

Question 41

no of orbitals in a shell formula

Answer 41

n^2

Question 42

max no of transitions of excited atom formula

Answer 42

n(n-1)/2

Question 43

when hydrogen gas is enclosed in a discharge tube using low pressure it emits

Answer 43

blue light

Question 44

which atom does have spin quantum number 1/2

Answer 44

odd mass number and odd atomic number

Question 45

as the attraction between the nucleus and the foreign electron increases, the P.E of the system

Answer 45

decreases