Structure of Atoms Flashcards
when did Rutherford perform an experiment?
1911
why did Rutherford perform an experiment?
he wanted to find the nature of atoms and the arrangement of electrons and protons within the atom.
the thickness of the gold foil?
0.00 004 cm
the alpha particles were obtained from?
disintegration of polonium (Po)
Rutherford’s atomic model resembles?
solar system
conclusion of Rutherford?
Defects of Rutherford’s atomic model?
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.
an electron ______ energy when it moves from higher energy to lower energy level?
emits
an electron ______ energy when it moves from lower energy to higher energy level?
absorbs
when does an electron emit energy?
when it moves from higher to lower energy level
when does an electron absorb energy?
when it moves from lower to higher energy level
Name the sub-shells.
4
s= 2e-
p= 6e-
d=10e-
f= 14e-
how many electrons can d sub-shell hold?
10 electrons
how many electrons can f sub-shell hold?
14 electrons
how many electrons can p sub-shell hold?
6 electrons
how many electrons can s sub-shell hold?
2 electrons
what are shells?
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.
As the value of n increases the ___________________?
distance of an electron from the nucleus and the energy of the shell increases.
how can we know the arrangement of electrons in shells?
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.
the energy of an electron in an orbit is proportional _____________________?
to its distance from the nucleus.
electron present in an orbit ________ radiate energy.
does/ does not
does NOT
what are isotopes?
isotopes are atoms of the same element that have the same atomic number but different mass numbers because of the difference in neutrons.
how many isotopes of hydrogen?
3
H-1 protium
H-2 deuterium
H-3 tritium
how many neutrons are in deuterium?
1 neutron
how many neutrons are in protium?
0 neutron
water that contains __________ atoms in place of __________ is called heavy water
H-2 (deuterium)
H-1(protium)
melting point of D2O?
3.81 degrees C
boiling point of heavy water?
101.2 degrees C
percentage composition of protium and deuterium?
99.99%
0.0015%
which isotope of hydrogen is radioactive?
Tritium Hydrogen-3
how many isotopes of carbon?
3
Carbon-12
Carbon-13
Carbon-14
how many neutrons are there in carbon-14?
8 nuetrons
how many neutrons are there in carbon-13?
7 nuetrons
percentage composition of carbon 13?
1.1%
percentage composition of carbon 14?
0.009%
percentage composition of carbon 12?
98.8%
how many isotopes of chlorine?
2
chlorine-35
chlorine-37
how many neutrons are in chlorine-35?
18 neutrons
how many neutrons are in chlorine-37?
20 neutrons
percentage composition of chlorine-35?
75%
75.77%
percentage composition of chlorine-37?
25&
24.23%
which uranium isotope is used in nuclear reactors and atomic bombs?
Uranium-235
which uranium isotope is rare?
Uranium 234
percentage composition of uranium- 235?
0.72%
percentage composition of uranium- 238?
99.27%
percentage composition of uranium- 234?
0.006%
how many protons are in chlorine?
17 protons
how many protons are in hydrogen?
1 proton
how many protons are in uranium?
92 protons
the nuclear energy released by the fission of 1kg of uranium _______ is equivalent to ________
235
the chemical energy released by burning more than 17 tonnes of coal.
which uranium isotope is rare?
U-234
state the auf bau principle?
in the ground state of an atom, electrons fill atomic orbitals of the lowest available energy level before occupying higher-energy levels.
what is electronic configuration?
the distribution or arrangement of electrons in the sub-shells of an atom.
which uranium isotope is used in nuclear reactors and atomic bombs?
uranium - 235
roman numerals
vertical lines in PT are called?
groups
the horizontal line in PT is called?
period/series
period no. determine _________?
no. of shells
how to determine the group of an element?
count the number of electrons in the valence shell.
how to write a symbol for any element?
X
mass number A: up
atomic number Z: down
why isotopes have same chemical properties?
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.
the energy of light transmitted is exactly equal to the ___________________.
difference between the energies of the orbits.
ΔE(light)=Ef−Ei
n value of shell is placed ________ the symbol for sub-shell.
before
2s
3p
