Structure of Atom 6 Flashcards
what is a node
the region where the probablity density of finding an e- is 0 is called nodal region or nodes
shape of s orbital
It is spherical around the nucleus and it is ymmetrical. the probability of
finding electron is same in all directions from the nucleus.
1s and 2 s and 3s are alll symmetrical and differ only in size, energy and no of nodes.
increase in n and increase in size nd energy
s orbita is sspherical and has only 1 oritentation. not aligned any specific axis
what gives no of nodes of s orbital
it has spherical/radial nodes.
no of nodes= n-1
what is e- cloud
e- cloud is the space around the nucleus which describes the probablity of finding an e- is terms of dots
what is boundary surface diagram
it is the representatin of the shape of orbital which encloses a region or volume where the probablity of finding an e- very high(90%)
Why
do we not draw a boundary surface diagram,
which bounds a region in which the probability
of finding the electron is, 100 %
The answer
to this question is that the probability density
|ψ|2
has always some value, howsoever
small it may be, at any finite distance from
the nucleus. It is therefore, not possible to
draw a boundary surface diagram of a rigid
size in which the probability of finding the
electron is 100%. Boundary surface diagram
for a s orbital is actually a sphere centred on
the nucleus. In two dimensions, this sphere
looks like a circle. It encloses a region in
which probability of finding the electron is
about 90%.
what is the shape of p orbital
P orbital has a dumbell shape with nucleus as the origin. Each of the section on each plane is callef lobe.
There are 3 p orbital each with a different orientation wrt coordinate axes.
The size, shape and
energy of the three orbitals are identical.
They differ however, in the way the lobes are
oriented.
Since the lobes may be considered to lie along the x, y or z axis, they are given the designations 2px, 2py, and 2pz
.
It should be
understood, however, that there is no simple
relation between the values of ml
(–1, 0 and +1)
and the x, y and z directions.
what are nodes for p orbital
The value of probablity density function is 0 at the plane where the two lobes touch each other. the probablity of finding an e- is maxiumum in the two lobes. There is a nodal plane passing through the nucleus where the probablitiy of finding an e- is 0.
in case of pz
orbital, xy-plane is a nodal plane, in case of
dxy orbital, there are two nodal planes passing
through the origin and bisecting the xy plane
containing z-axis. These are called angular
nodes and number of angular nodes are given
by ‘l’,
shape of d orbitals
For l = 2, the orbital is known as d-orbital
and the minimum value of principal quantum
number (n) has to be 3. as the value of l cannot
be greater than n–1. There are five ml
values
(–2, –1, 0, +1 and +2) for l = 2 and thus there
are five d orbitals.
The five d-orbitals are designated as dxy,
dyz, dxz, dx2–y2 and dz2. The shapes of the first
four d-orbitals are similar to each other, where
as that of the fifth one, dz2, is different from
others, but all five 3d orbitals are equivalent
in energy. The d orbitals for which n is greater
than 3 (4d, 5d…) also have shapes similar to
3d orbital, but differ in energy and size.
total number of nodes
The
total number of nodes are given by (n–1),
i.e., sum of l angular nodes and (n – l – 1)
radial nodes.
what is ground state
The ground state of an electron, the energy level it normally occupies, is the state of lowest energy for that electron.
what is excited state
When an electron temporarily occupies an energy state greater than its ground state, it is in an excited state.
what are degenerate orbitals
orbitals which have same energy
4s<3d and 6s<5d; 4f<6p.
why is that
The main
reason for having different energies of the
subshells is the mutual repulsion among the
electrons in multi-electron atoms. The only
electrical interaction present in hydrogen
atom is the attraction between the negatively
charged electron and the positively charged
nucleus. In multi-electron atoms, besides the
presence of attraction between the electron
and nucleus, there are repulsion terms
between every electron and other electrons
present in the atom. Thus the stability of an
electron in a multi-electron atom is because
total attractive interactions are more than
the repulsive interactions.
what is screening or shielding rule
In general, the
repulsive interaction of the electrons in the
outer shell with the electrons in the inner shell
are more important. On the other hand, the
attractive interactions of an electron increases
with increase of positive charge (Ze) on the
nucleus. Due to the presence of electrons in
the inner shells, the electron in the outer shell
will not experience the full positive charge of
the nucleus (Ze). The effect will be lowered
due to the partial screening of positive charge
on the nucleus by the inner shell electrons.
This is known as the shielding of the outer
shell electrons from the nucleus by the
inner shell electrons, and the net positive
charge experienced by the outer electrons is
known as effective nuclear charge (Zeff e).
