The document discusses the history and properties of atoms. It describes atoms as the smallest unit of matter, first proposed by Greek philosophers. John Dalton established atoms as the building blocks of elements with unique properties. The structure of atoms was further elucidated by scientists like Thomson, Rutherford, Bohr, and Schrodinger, who discovered atoms have a tiny, dense nucleus surrounded by orbiting electrons. Atoms bond through ionic, covalent, and metallic bonds to form molecules and matter in various states. Matter is anything that has mass and occupies space, and can be transformed between different states while obeying the law of conservation of matter.

3. Atom
- smallest unit of a chemical element.
- is the smallest part of an element that has all
the properties of that element.
- it is the smallest unit of matter.
- coined by the Greek meaning “indivisible”( α
+ τεμον)

4. Atom
- smallest unit of a chemical element of matter.
- The Atom is the building block of the
radiographer’s understanding of the interaction
between ionizing radiation and the matter.
Although atoms are too small to be seen with our
eyes, scientists have long had indirect evidence for
the existence of atoms.

5. The Greek Atom
According to the ancient Greek philosophers, all matter
could be described as a combination of substances, (AIR,
EARTH, WATER, FIRE) and modified by four basic essences
(WET, DRY, HOT, COLD).

6. Dalton’s Atom
In 1808, John Dalton, published a book
summarizing his experiments, which showed
that the elements could be classified according
to integral values of atomic number. According
to Dalton, an element was composed of
identical atoms, each has acting the same way
chemical reactions.

7. All oxygen atoms were alike. They looked
alike, they were constructed alike, and they
reacted alike. They were, however very
different from atoms of any other element.
The physical combination of one type of atom
with another was interpreted as being a hook-
and-eye affair. The size and number of the
hooks and eyes were different for each
element.

8. Dmitri Mendeleev
50 years after Dalton’s work, he showed
that if the elements were arranged in order of
increasing atomic mass, repetition of similar
chemical properties occurred. Mendeleev’s
work resulted in the first periodic table of
elements.

9. Joseph John Thomson’s Atom
Proposed an early model of the atom,
called the plum pudding model, in 1899. He
described the atom as a sphere of positively
charge containing a few negatively – charged
particles, called electrons, distributed in the
sphere like raisins in a plum pudding.

10. Ernest Rutherford Atom’s Atom
A British physicist who learned from
experiments that the positive charge in an atom and
most of the atom’s mass must be concentrated in a
small, central region, called the nucleus. He proposed
that electrons carrying negative charge orbited the
nucleus like planets orbiting in a solar system.

11. Niels Bohr Atom’s Atom
Discovered that the electrons in
atoms had certain values of energy. He
proposed that the energy of an electron
was related to the distance at which the
electron orbited the nucleus.

12. Electrons, therefore, orbited only at
certain distances that corresponded to
these allowed energies. He called these
orbits quantized orbits, because they
corresponded certain quantities of
energy.

13. Erwin Schrodinger’s Atom
introduced a revolutionary change to the model
of the atom in 1925. He proposed that electrons do
not orbit the nucleus but behave more like waves
traveling at certain distances and with certain
energies around the nucleus. This model proved to
be the most accurate. Physicist no longer tries to find
an electron’s path and position in an atom.

14. Elementary Particles
1. Proton
2. Neutron
3. Electron
Particle Location Relative Mass Kilogram AMU Number Charge Symbol
Electron Shells 1 9.109x10 -31 0.000549 0 -1 -
Proton Nucleus 1836 1.673x10 -27 1.00728 1 +1 +
Neutron Nucleus 1838 1.675x10- 27 1.00867 1 0 0

15. Parts of an Atom
1. Nucleus
2. Orbital Shells

16. Atomic Properties
The atom’s electron cloud, that is, the
arrangement of electrons around an atom,
determines most of the atom’s physical and chemical
properties The electrons in the outermost shell
largely determine the chemical properties of an atom.
If this shell is full, meaning all the orbitals in the
shell have two electrons, then the atom is stable, and
it won’t react readily with other atoms. If the shell is
not full, the atom will chemically react with other
atoms, exchanging or sharing electrons in order to fill
its outer shell. Atoms bond with other atoms to fill
their outer shells because it requires less energy to
exist in this bonded state. Atoms always seek to exist
in the lowest energy state possible.

17. Atomic Bonds
In a covalent bond, the two bonded atoms share
electrons.
Ionic Bond - Atoms can also lose or gain
electrons to complete their valence shell. Atoms with
net electric charge are called ions. Scientists call
atoms with a net positive electric charge cations and
atoms with a net negative electric charge anions.
Metallic Bonds - Atoms can complete their
valence shells in a third way: by bonding together in
such a way so that all the atoms in the substance
share each other’s outer electrons.

18. 4 ATOMIC
CONFIGURATIONS
1. ISOTOPE – atoms that have the same atomic
number but different atomic mass number.
2. ISOBAR – atomic nuclei that have the same
atomic mass number but different atomic
number.

19. 3. ISOTONE – atoms that have the same
number of neutrons but different number
of protons. These are atoms with different
atomic numbers and different atomic mass
numbers but a constant value for the
quantity.
4. ISOMER – final category of atomic
configuration. Have the same atomic
number and the same atomic mass number.

21. Matter
- is the substance of which physical objects are
composed.
- anything that occupies space and has mass/weight.
- It is the material substance with form and shape
composing physical objects.
The fundamental building blocks of matter are
atoms and molecules.

22. Mass - the quantity of matter
contained in a physical object.
Weight - the mass of an object
in a gravitational field

23. States of Matter

24. Law of Conservation of Matter
Matter cannot be created nor destroyed
but can be transformed from one state into
another.

25. Scientists have long known that matter
can be converted to energy and, conversely,
energy can be convert. In 1905 physicist Albert
Einstein quantified the relationship between
matter and energy in his famous equation
e=mc2, in which E is energy, m is mass, and c is
the speed of light (300,000 km/sec [186,000
mi/sec]).ed to matter. In an atomic bomb
blast, a very small amount of matter is
converted to its equivalent in energy, creating
an immense explosion.

26. Scientists have also created matter from
energy by bombarding heavy atoms (atoms
made up of many protons and neutrons) with
high-energy radiation in the form of X rays.
Collisions between the X-ray beam and the
atoms created matter in the form of sets of
electron and positron particles, a phenomenon
known as pair production. Positrons are
particles that have the same weight and
amount of charge as electrons, but positrons
are positively charged, while electrons are
negatively charged.

27. Antimatter
- it is a matter that is composed of
antiparticles in the same way that
normal matter is composed of
particles.

28. Ex: An antielectron(positron) and an
antiproton could form an antihydrogen
atom in the same way that an electron and
a proton form a normal matter hydrogen
atom.

29. Antimatter is not found naturally on
Earth, except very briefly and in
vanishingly small quantities as the result
of radioactive decay or cosmic rays. This
is because antimatter that came to exist
on Earth outside the confines of a
suitable physics laboratory would almost
instantly meet the ordinary matter that
Earth is made of, and be annihilated.

30. Law of Conservation of Matter
Matter cannot be created nor destroyed
but can be transformed from one state into
another.