Structure of Atoms

Question 1

when did Rutherford perform an experiment?

Answer 1

1911

Question 2

why did Rutherford perform an experiment?

Answer 2

he wanted to find the nature of atoms and the arrangement of electrons and protons within the atom.

Question 3

the thickness of the gold foil?

Answer 3

0.00 004 cm

Question 4

the alpha particles were obtained from?

Answer 4

disintegration of polonium (Po)

Question 5

Rutherford’s atomic model resembles?

Answer 5

solar system

Question 6

conclusion of Rutherford?

Question 7

Defects of Rutherford’s atomic model?

Answer 7

Any particle in a circular orbit undergoes acceleration. During acceleration, charged particles would radiate energy. Thus, the revolving electron would lose energy and finally fall into the nucleus. If this were so, the atom should be highly unstable.

Question 8

an electron ______ energy when it moves from higher energy to lower energy level?

Answer 8

emits

Question 9

an electron ______ energy when it moves from lower energy to higher energy level?

Answer 9

absorbs

Question 10

when does an electron emit energy?

Answer 10

when it moves from higher to lower energy level

Question 11

when does an electron absorb energy?

Answer 11

when it moves from lower to higher energy level

Question 12

Name the sub-shells.

Answer 12

4
s= 2e-
p= 6e-
d=10e-
f= 14e-

Question 13

how many electrons can d sub-shell hold?

Answer 13

10 electrons

Question 14

how many electrons can f sub-shell hold?

Answer 14

14 electrons

Question 15

how many electrons can p sub-shell hold?

Answer 15

6 electrons

Question 16

how many electrons can s sub-shell hold?

Answer 16

2 electrons

Question 17

what are shells?

Answer 17

According to Bohr’s atomic theory, the electron in an atom revolves around the nucleus in one of the circular paths called shells or orbits. Each shell has a fixed energy. So, each shell is also called an energy level. Each shell is described by an n value.

Question 18

As the value of n increases the ___________________?

Answer 18

distance of an electron from the nucleus and the energy of the shell increases.

Question 19

how can we know the arrangement of electrons in shells?

Answer 19

by using the 2n2 formula
2 (number of shell) raised to 2
2x3 2
2x9
18
so, the third shell can hold max. of 18 electrons.

Question 20

the energy of an electron in an orbit is proportional _____________________?

Answer 20

to its distance from the nucleus.

Question 21

electron present in an orbit ________ radiate energy.
does/ does not

Answer 21

does NOT

Question 22

what are isotopes?

Answer 22

isotopes are atoms of the same element that have the same atomic number but different mass numbers because of the difference in neutrons.

Question 23

how many isotopes of hydrogen?

Answer 23

3
H-1 protium
H-2 deuterium
H-3 tritium

Question 24

how many neutrons are in deuterium?

Answer 24

1 neutron

Question 25

how many neutrons are in protium?

Answer 25

0 neutron

Question 26

water that contains __________ atoms in place of __________ is called heavy water

Answer 26

H-2 (deuterium) H-1(protium)

Question 27

melting point of D2O?

Answer 27

3.81 degrees C

Question 28

boiling point of heavy water?

Answer 28

101.2 degrees C

Question 29

percentage composition of protium and deuterium?

Answer 29

99.99% 0.0015%

Question 30

which isotope of hydrogen is radioactive?

Answer 30

Tritium Hydrogen-3

Question 31

how many isotopes of carbon?

Answer 31

3 Carbon-12 Carbon-13 Carbon-14

Question 32

how many neutrons are there in carbon-14?

Answer 32

8 nuetrons

Question 33

how many neutrons are there in carbon-13?

Answer 33

7 nuetrons

Question 34

percentage composition of carbon 13?

Answer 34

1.1%

Question 35

percentage composition of carbon 14?

Answer 35

0.009%

Question 36

percentage composition of carbon 12?

Answer 36

98.8%

Question 37

how many isotopes of chlorine?

Answer 37

2 chlorine-35 chlorine-37

Question 38

how many neutrons are in chlorine-35?

Answer 38

18 neutrons

Question 39

how many neutrons are in chlorine-37?

Answer 39

20 neutrons

Question 40

percentage composition of chlorine-35?

Answer 40

75% 75.77%

Question 41

percentage composition of chlorine-37?

Answer 41

25& 24.23%

Question 42

which uranium isotope is used in nuclear reactors and atomic bombs?

Answer 42

Uranium-235

Question 43

which uranium isotope is rare?

Answer 43

Uranium 234

Question 44

percentage composition of uranium- 235?

Answer 44

0.72%

Question 45

percentage composition of uranium- 238?

Answer 45

99.27%

Question 46

percentage composition of uranium- 234?

Answer 46

0.006%

Question 47

how many protons are in chlorine?

Answer 47

17 protons

Question 48

how many protons are in hydrogen?

Answer 48

1 proton

Question 49

how many protons are in uranium?

Answer 49

92 protons

Question 50

the nuclear energy released by the fission of 1kg of uranium _______ is equivalent to ________

Answer 50

235 the chemical energy released by burning more than 17 tonnes of coal.

Question 51

which uranium isotope is rare?

Answer 51

U-234

Question 52

state the auf bau principle?

Answer 52

in the ground state of an atom, electrons fill atomic orbitals of the lowest available energy level before occupying higher-energy levels.

Question 53

what is electronic configuration?

Answer 53

the distribution or arrangement of electrons in the sub-shells of an atom.

Question 54

which uranium isotope is used in nuclear reactors and atomic bombs?

Answer 54

uranium - 235

Question 55

roman numerals

Question 56

vertical lines in PT are called?

Answer 56

groups

Question 57

the horizontal line in PT is called?

Answer 57

period/series

Question 58

period no. determine _________?

Answer 58

no. of shells

Question 59

how to determine the group of an element?

Answer 59

count the number of electrons in the valence shell.

Question 60

how to write a symbol for any element?

Answer 60

X mass number A: up atomic number Z: down

Question 61

why isotopes have same chemical properties?

Answer 61

chemical properties depend on no. of protons and electrons. Neutrons don't take part in chemical reactions. | no. of neutrons do not matter in chemical properties.

Question 62

the energy of light transmitted is exactly equal to the ___________________.

Answer 62

difference between the energies of the orbits. ΔE(light)=Ef−Ei

Question 63

n value of shell is placed ________ the symbol for sub-shell.

Answer 63

before 2s 3p