KERALA PSC / CHEMISTRY / STRUCTURE OF AN ATOM / NOTES
/ OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC
PRELIMINARY
KERALA PSC / CHEMISTRY / STRUCTURE OF AN ATOM / NOTES
/ OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC
PRELIMINARY
·
The
central part of atom is called nucleus. Protons and neutrons are present in
nucleus and electrons are revolving around the nucleus in definite path called
orbits
·
Electron
is a fundamental particle of an atom which carries a unit negative change. It was
discovered by J.J Thomson (1987) from the studies carried out on cathode rays
in the discharge tube.
·
Presence
of Protons was observed by Goldstein in 1896 in a discharge tube with a
perforated cathode. Experiments carried out by Lord Rutherford showed that
positive particles produced in a discharge tube containing hydrogen gas are
same as protons
·
Neutrons
are about the same size as protons but have no electric charge. Neutrons are
bound very tightly in the atoms nucleus with the protons.
·
Mass
number is the sum of
number of protons and neutrons present in the nucleus of an atom.
·
¹²C is international standard for atomic mass measurements.
·
Atomic
number is derived from
Nuclear charge of atom, hence it will be the number of protons
·
Electron
is the fundamental particle of matter or nature
·
Heaviest
sub-atomic particle is Neutron
·
Electrons
and protons have same mass and opposite charges
·
Antineutrons
have no charge and no mass
·
The
dual nature of electron was proposed by Victor de-Broglie
·
The
dual nature of electrons was experimentally provided by I.H Germer
·
The
radius of nucleons of an atom varies in the order 10¯¹³ cm.
·
Isotopes
are the different types of atoms of the same element having same atomic number
and different mass numbers
·
Isotopes
differ in the number of neutrons
·
Protium,
Deuterium and Tritium are the Isotopes of Hydrogen
·
Protium
has no neutron
·
Deuterium
has one neutron
·
Tritium
has two neutrons
·
Isobars
are atoms of different elements having same mass number and different atomic
numbers, Eg. Argon -40 and Calcium 40
·
Isotones:
are atoms of
different elements having different atomic numbers, and mass numbers, but they
have same number of neutrons. Eg: ³₁H and ⁴₂He, both contain two
neutrons
·
Nuclear
Isomers: These are the
different types of atoms of the same element having different radioactivity
constants
·
The
term ‘isotope’ was introduced by Soddy
·
Allotropes
are different
forms of the same element with different physical appearances. Eg: Red
phosphorus and white phosphorus, oxygen and ozone
·
Carbon
exists in crystalline as well as amorphous allotropes
·
Noble
gases have zero valency
·
Hydrogen
shows univalency
·
Sodium
and Potassium show univalency
·
The
common valency of carbon is four
·
Carbon
has maximum tendency of catenation (self linking property) in comparison to any
other element in the periodic table.
·
Cathode
rays are discovered by Julius Plucker
·
Anode
rays are discovered by Goldstein
·
Neutron
was discovered by James Chadwick
·
Cathode
rays are used in Television
·
The
atomic size is about 10⁵ times larger than the nuclear size
·
Wavelength
of violet (VIBGYOR) is 3800 Aº - 4300 Aº
·
Wavelength
of Red is 6500 Aº - 7600 Aº
·
The
most valid atomic theory was “Wave mechanical model of atom” suggested by Max
Planck
·
Spectroscope
is an instrument which analyses the wavelength of emitted radiations
·
The
radioactive liquid element is Francium
·
The
radioactive gaseous element is Radon
·
The
atomic number was first calculated by Moseley
·
The
most reactive element – fluorine
·
The
most complex atom available from earth is Uranium – 238
·
The
densest element: Osmium
·
The
lightest element: Hydrogen
·
The
lightest metal: Lithium
·
Actinometer
is used to measure the intensity of radiation
KERALA PSC / CHEMISTRY / STRUCTURE OF AN ATOM / NOTES
/ OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC
PRELIMINARY
