2. A. Atomic Spectrum
atomic spectrumThe range of characteristic frequencies
of electromagnetic radiation that are readily absorbed and
emitted by an atom. The atomic spectrum is an effect of
the quantized orbits of electrons around the atom. An
electron can jump from one fixed orbital to another: if the
orbital it jumps to has a higher energy, the electron must
absorb a photon of a certain frequency; if it is of a lower
energy, it must give off a photon of a certain frequency.
The frequency depends on the difference in energy
between the orbitals. Explaining this phenomenon was
crucial to the development of quantum mechanics. The
atomic spectrum of each chemical element is unique and
is largely responsible for the color of matter. Atomic
spectra can also be analyzed to determine the
composition of objects, such as stars, that are far away.
See more at orbital, See also spectrum.
3. A.) Colors of vaporized element.
( Using Flame test)
5. 2) The weigh particle
models
This past year has seen a fair amount of excitement in the
particle-physics community, with bumps and jumps and
leaks and debates, but sadly without any spectacular
discoveries. In fact, since the both the CDF and D0
experiments at the US Fermi National Accelerator
Laboratory (Fermilab) reported the production of the top
quarks in 2009, it’s been rather quiet on the particle front.
So it was quite refreshing to hear that researchers at
the CDF collaboration at Fermilab announced the
observation of a new particle – the neutral “Xi-sub-bThis
particle is basically a baryon – a Standard Model particle
that is formed of a combination of three quarks.
6. Common examples of baryonic particles are the proton – a
combination of two up quarks and a down quark and the
neutron – a combination of two down quarks and an up quark.
This new addition consists of a strange quark, an up quark
and a bottom quark (s-u-b). While its existence was predicted
by the Standard Model, the observation of the neutral Xi-sub-b
is significant because it strengthens our understanding of how
quarks form matter. This new particle fits into the bottom
baryons group, which are six times heavier than the proton
and neutron because they all contain a heavy bottom quark.
The particles are produced only in high-energy collisions, and
are rare and very difficult to observe.
Once produced, the neutral Xi-sub-b travels a fraction of a
millimetre before it decays into lighter particles.
7. . Combing through
almost 500 trillion
proton–antiproton
collisions produced by
researchers isolated
25 examples in which
the particles emerging
from a collision bore
the signature of the
neutral Xi-sub-b. The
analysis established
the discovery at a level
of 7 sigma, clearing the
5 sigma threshold quite
easily. (Image
courtesy: Fermilab)
8. 3) Fundamental particles of
atoms
Baryons, subatomic particle that is
composed of three smaller particles
called quarks. Two of the particles found
in atoms are baryons: the proton and
the neutron. Protons and neutrons
combine with particles called electrons
to make atoms.
9. Meson, any member of a class
of tiny particles that make up
matter. Mesons are composed
of smaller particles called
quarks and antiquarks. Quarks
and antiquarks are elementary
particles, particles so small and
basic that they cannot be
divided.
10. Antibaryons
Baryons are characterized by a baryon
number, B, of 1. Their antiparticles,
called antibaryons, have a baryon
number of −1. An atom containing, for
example, one proton and one neutron
(each with a baryon number of 1) has a
baryon number of 2. In addition to their
differences in composition, baryons and
mesons can be distinguished from one
another by spin.
11. Quarks
Quark, smallest known building
block of matter. Quarks never
occur alone; they always are
found in combination with other
quarks in larger particles of
matter.
12. Isotopes
Isotope, one of two or more species of
atom having the same atomic number,
hence constituting the same element, but
differing in mass number. As atomic
number is equivalent to the number of
protons in the nucleus, and mass number
is the sum total of the protons plus the
neutrons in the nucleus, isotopes of the
same element differ from one another only
in the number of neutrons in their nuclei.
13. Percentage abundance
Let’s take an example. Copper consists mainly
of two isotopes, 63Cu and 65Cu, and its
(average) atomic mass is 63.55 (to 2 d.p.)
Let’s assume next that the percentage
abundance of 63Cu is x
This means that the percentage abundance
of 65Cu will be 100-x
14. Given 100 random copper atoms, x will each have a
mass of 63 [total mass = 63x]
And 100-x will have a mass of 65 [total mass = (100-x) x
65 = 6500-65x]
So the total mass of 100 atoms = 63x + 6500–65x =
6500–2x
This means that the average mass = (6500–2x) / 100
But we are told in the question that average mass =
63.55
Therefore (6500-2x) / 100 = 63.55
So 6500–2x = 6355
Hence 2x = 6500-6355 = 145
And x = 72.5
So, in a typical sample of copper 72.5% of the atoms
are 63Cu and 27.5% are 65Cu.
