- Dalton's model proposed that all matter is made of tiny particles called atoms, all atoms of the same element are alike but different from other elements, and compounds form from atoms combining in fixed proportions. Thomson's model pictured the atom as a positively charged sphere with electrons embedded within it. Rutherford's model showed that the atom's positive charge and most of its mass are concentrated in a tiny, dense nucleus at the center with electrons orbiting outside. The parts of an atom include the nucleus containing protons and neutrons at its center, surrounded by electrons. Protons have a positive charge while neutrons have no charge. Electrons have a negative charge and much less mass than protons or neutrons.

1. STRUCTURE OF AN ATOM
BY IRA DEOKULE VIII J ROLL NO. 6

2. Developments in the model
of atom

3. Dalton’s Model
Also known as the billiard ball model
• All matter is made up of tiny
particles called atoms.
• All atoms of a given element are
a like, but are different from the
atoms of any other element.
• Compounds are formed when
atoms of different elements
combine in fixed proportions.
• A chemical reaction involves a
rearrangement of atoms, not a
change in the atoms themselves.

4. Thomson’s Model
Also known as the plum pudding or water melon model

5. Rutherford’s Model
• The atom's electron cloud does not influence
alpha particle scattering.
• Much of an atom's charge (specifically, its
positive charge) is concentrated in a relatively
tiny volume at the nucleus.
• The magnitude of this charge is proportional to
(up to a charge number that can be
approximately half of) the atom's atomic mass -
the remaining mass is now known to be mostly
attributed to neutrons.
• This concentrated central mass and charge is
responsible for deflecting both alpha and beta
particles.
• The mass of heavy atoms such as gold is mostly
concentrated in the central charge region.

6. Parts of the atom

7. Nucleus
• A model of the atomic nucleus
showing it as a compact bundle of
the two types of nucleons: protons
and neutrons.
• In simple diagrams they look like little
balls stuck together but an actual
nucleus cannot be explained like this
but only by using quantum
mechanics.
• In a nucleus which occupies a
certain energy level each nucleon
can be said to occupy a range of
locations.

8. Neutron
• The neutron is a subatomic particle
with no electric charge.
• The nucleus consists of a number
of protons and neutrons.
• The mass of the neutron is slightly
larger than that of proton.
• In the nucleus, the protons and
neutrons are bound together
through nuclear force and
neutrons are needed for the
stability of the nuclei.
• Even though it is not a chemical
element it is included in the table
of nuclides.

9. Protons
• The proton is subatomic particle
with a positive electric charge.
• The nucleus consists of a number
of protons and neutrons.
• The mass of the proton is slightly
larger than that of neutron.
• The number of protons in the
nucleus is referred to as it’s
atomic number.

10. Electrons
• The electron is a subatomic
particle with a negative charge.
• The mass of the electron is
approximately 1/1836 that of
proton.
• An electron generates a magnetic
field.
• Electrons have many applications,
including electronics, welding,
cathode ray tubes, electron
microscopes, radiation therapy,
lasers, gaseous ionization detectors
and particle accelerators etc.

11. Thank You