Quantum Numbers - Mass, Charge, Spin physics presentation

1. QUANTUM NUMBERS –
MASS, CHARGE, SPIN
S.AHAMED YOONUS,
I181104.
By,

2. QUANTUM NUMBERS
• A quantum number is a value that is used when describing the
energy levels available to atoms and molecules.
• An electron in an atom or ion has four quantum numbers to describe
its state and yield solutions to the Schrödinger wave equation for the
hydrogen atom.
• There are 4 quantum numbers,
• n-principle quantum number : describes the energy level
• l-azimuthal quantum number: describes the subshell
• m-magnetic quantum number: describes the orbital of the subshell
• s-spin quantum number

4. MASS

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7. • From a relativistic point of view, mass-energy is the total amount of energy
of a body as expressed in Einstein’s E = mc2.
Individual particles may have mass. The electron is often said to have no
mass but actually has a small amount: 1/1,836 that of a proton. To be
precise, the mass of an electron is 9.10938291 × 10-31 kg. The electron’s
small mass means a tiny force can accelerate it to a high speed.
• By convention, photons are considered to be massless. But photons do
possess energy and according to Einstein’s theory of Relativity, backed up
by ample experiment and observation, energy and mass are related by E =
mc2. According to this equation, photons do indeed have a certain mass.
• Notwithstanding, it is generally said that the photon is totally without mass.
Were it to have a definite mass, it would not move at the “speed of light” in a
vacuum. It would travel at a lower speed dependent upon frequency. With
any mass at all, light particles would travel at the speed of gravitons.
• The mass of a proton is 1.67262178 × 10-27 kg. While much more massive
than an electron or the ghostly photon, this is still a tiny number.
• Because it has no charge, the mass of a neutron cannot be measured by
means of mass spectrometry. It is considered to be slightly greater than the
mass of a proton.

8. CHARGE
• Besides mass, one of the attributes often but not always
exhibited by atomic particles and matter is charge. It is defined
as a property of matter that makes it experience a force when
placed in a magnetic field. Besides being influenced by
electromagnetic fields, electrically charged matter also
produces them.
• As ancients discovered and children with inquiring minds
quickly learn, unlikes attract and likes repel one another. This
is true of both magnets and electrically charged objects.

9. FIELD LINES AND EQUIPOTENTIALS AROUND
AN ELECTRON, A NEGATIVELY CHARGED
PARTICLE.

10. • The basic unit of charge is the electron, and it is considered to
be negative, although this is a matter of semantics. Because
electrical current consists of a flow of electrons, it might be
more appropriate to consider the electron as carrying a positive
charge, but it is too late for that.
• In line with quantum physics, it has been amply demonstrated
that the unit of electrical charge is quantized. What this means
is that at the small end of things there exists a minimum
electrical charge that cannot be further subdivided, although
this statement must be modified in the strange case of the
quark.
• For the most part, charge on a macro scale exists in integer
multiples of the elementary charge, denoted e, which is
approximately 1.602 × 10-19 coulombs.

11. • Robert Millikan is credited with determining the exact electrical
charge of an electron. He measured the speed of water droplets
through an electric field. Finding that water evaporated too
quickly, he later substituted oil drops. He found the charge on
the droplets was always a multiple of a single amount, and by
simple division the elementary charge was found.
• The electron, again by convention, defines the elementary
charge as –e. In line with this, the elementary charge of a
proton is +e. Because of their mutual attraction, the electron
remains in orbit around an atom’s nucleus. Protons, despite
their like charges, remain tightly bound together in the nucleus
of an atom, thanks to their strong attraction to the neutrons.
The atomic nucleus remains stable unless otherwise persuaded
by the gentle ministrations of atomic weapon makers or
producers of the energy that converts water to steam in order

12. SPIN
• A third property, spin, is still more elusive. The basic concept is
familiar. We all know that the earth, like many spherical bodies,
turns on its axis. It is said to have angular momentum that
does not change, slow down or speed up, unless force or
friction is applied.
• This angular momentum principle is illustrated by that
wonderful nineteenth-century mechanism, the centrifugal fly-
ball governor, used to regulate a steam engine’s speed of
rotation. Any change in angular momentum will let the
weighted spheres move upward or downward toward the center
of the earth, making for change in RPM. Linkage to a steam
intake valve adjusts engine torque to regulate speed.

13. A classic flyball governor

14. • All of this is in accord with Newtonian physics. But in the quantum realm of the
super small, the situation with regard to spin is altogether different. A simplistic
notion would be to conceive of elementary particles as rotating about their axes
much like astronomical bodies such as the earth. This is true in that the
mathematical laws that are applicable to quantized angular momentum are
valid. But there are differences between these phenomena.
• The direction of an elementary particle’s spin can change, but the speed of
rotation for any given elementary particle is fixed, and that is what determines
the quantum number. Depending on the type of particle, the quantum number
may be expressed as half-integer values.
• Bosons have integer spins, such as 0, 1 and 2. Fermions have half-integer spins,
such as 1/2, 3/2 and 5/2. Fermions conform to the Pauli exclusion principle.
Bosons do not, meaning that two bosons may have the same time and space co-
ordinates.
• By definition, true elementary particles such as the electron cannot be further
subdivided. Accordingly, spin must be seen as an intrinsically basic physical
property, in the same category as mass and charge.
• But whereas mass and charge accrete when elementary particles join to work in
concert, spin is quite different. The spin of a composite particle, such as a
helium atom, is different from that of the elementary particles from which it is