MATTER
• Matter is defined as anything that occupies space and has a definite
mass.
• Every matter consists of basic entities called elements.
• Each element is composed of smallest particles called ‘ATOM’.
• Atom- the name is derived from Greek language Atomos means ‘Not
to be cut’.
ATOMIC STRUCTURE
• Atom consists of positively charged NUCLEUS at the centre
and negatively charged Electrons revolving around it.
• Nucleus consists of Protons and Neutrons together called
Nucleons.
• Most of the mass of an Atom is possessed by Nucleus.
• The atomic number of an element describes the total number of
protons in its nucleus.
, Representation of an Atom
• The mass number (A), also called atom
number or nucleon number, is the total
of protons and neutrons (together kn
nucleons) in an atomic nucleus.
Atomic number of X = Mass number of
of neutrons
• Atomic number is defined as the numb
Example: protons present in an atom of an elemen
235U X-Uranium
92
Mass number (A) is 235
Atomic number(Z) is 92
,
, Introduction to Radioactivity
Radioactivity occurs at the atomic level when an atom has too much energy.
Atoms with too much energy release that energy as “radiation.”
Radiation is energy traveling in the form of particles or bundles of energy in
form. Some everyday examples of the energy bundles are microwaves used to coo
radio waves for radio and television, light, and X-rays used in medicine.
Many elements have radioactive atoms. The radioactivity of the element is the d
the atoms spit out the excess energy.
• Matter is defined as anything that occupies space and has a definite
mass.
• Every matter consists of basic entities called elements.
• Each element is composed of smallest particles called ‘ATOM’.
• Atom- the name is derived from Greek language Atomos means ‘Not
to be cut’.
ATOMIC STRUCTURE
• Atom consists of positively charged NUCLEUS at the centre
and negatively charged Electrons revolving around it.
• Nucleus consists of Protons and Neutrons together called
Nucleons.
• Most of the mass of an Atom is possessed by Nucleus.
• The atomic number of an element describes the total number of
protons in its nucleus.
, Representation of an Atom
• The mass number (A), also called atom
number or nucleon number, is the total
of protons and neutrons (together kn
nucleons) in an atomic nucleus.
Atomic number of X = Mass number of
of neutrons
• Atomic number is defined as the numb
Example: protons present in an atom of an elemen
235U X-Uranium
92
Mass number (A) is 235
Atomic number(Z) is 92
,
, Introduction to Radioactivity
Radioactivity occurs at the atomic level when an atom has too much energy.
Atoms with too much energy release that energy as “radiation.”
Radiation is energy traveling in the form of particles or bundles of energy in
form. Some everyday examples of the energy bundles are microwaves used to coo
radio waves for radio and television, light, and X-rays used in medicine.
Many elements have radioactive atoms. The radioactivity of the element is the d
the atoms spit out the excess energy.
