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ATOMS
Presentation by
Ruby group
the building block ATOMS
the building block ATOMS
Atomic Structure
 Atoms are composed of 2 regions:
 Nucleus: the center of the atom that contains the mass of the
atom
 Electron cloud: region that surrounds the nucleus that contains
most of the space in the atom
Nucleus
Electron
Cloud
Three subatomic particles make up every atom:
Subatomic
Particle
Charge Location Charge
(coulombs)
mass
Proton Positive (+) Nucleus or
“Core”
+1.6 x 10-19 1.67 x 10-24
Neutron No Charge (0) Nucleus or
“Core”
0 1.67 x 10-24
Electron Negative (-) Electron Cloud -1.6 x 10-19 9.1 x 10-28
Notice the smaller
particles that make
up this neutron
after you take a
closer look.
+
Notice the smaller
particles that make up
this proton after you
take a closer look.
the building block ATOMS
Democritus (460 - 370 BC)
the building block ATOMS
4. Atoms cannot be created, divided into smaller
particles, or destroyed. The law of conservation of mass
**In a chemical reaction, atoms of different elements are separated,
joined or rearranged. They are never changed into the atoms of
another element.
5. Atoms combine in definite whole number ratios to
make compounds (you can’t have a ½ of a Carbon bonding
with Oxygen; it’s a whole atom or no atom)
Dalton’s Atomic Theory (1803)
Atomic Theory
TimelineScientist Information Model
John
Dalton
All matter is made of
atoms. Atoms are too
small to see, indivisible
and indestructible. All
atoms of a given element
are identical. And are not
further divisible.
John Dalton (1766-1844)
• Dalton is the “Father of Atomic
Theory”
• John Dalton was first modern
scientist to give the concept of
atom
• Dalton’s ideas were so brilliant
that they have remained
essentially intact up to the
present time and has only
been slightly corrected.
Atomic Theory
TimelineScientist Information Model
J.J
Thompson
Discovered the negative
electron, and predicted
that there also must be a
positive particle to hold
the electrons in place.
JJ Thomson (1856-1940)
• Used cathode rays to
prove that Dalton’s Solid-
ball model could be broken
into smaller particles
•Thomson is credited with
discovering electrons
Thomson’s Plum Pudding Model
•Thomson’s Plum Pudding model is a + charge
sphere that has (- )charged electrons scattered
inside, like “raisins” in “plum pudding”.
•Overall, the atom is neutral atom because the
atom had the same number of positive and
negative charges.
•From Thomson’s experiments, scientists concluded that
atoms were not just neutral spheres, but somehow were
composed of electrically charged particles.
Atomic Theory
TimelineScientist Information Model
Ernest
Rutherford
Discovered the nucleus of an
and named the positive particles
in the nucleus “protons”.
Concluded that electrons are
scattered in empty space around
the nucleus.
Ernest Rutherford (1871-1937)
Learned physics in J.J.
Thomson’ lab.
Noticed that ‘alpha’
particles were
sometime deflected
by something in the
air.
Gold-foil experiment
Rutherford’s alpha scattering experiment.
source of
alpha particles
thin gold foil
photographic film
beam of a particles
most pass
straight
through
1 in 20 000
deflected
Rutherford’s explanation.
atoms of gold
in gold foil
Path of an a particle
nucleus of
gold atom
All these a particles pass
straight through the empty
space that makes up most of
the atom.
This a particle
passes close
enough to
nucleus to be
repelled
As a particles are positively charged,
the nucleus must contain positively
charged protons.
atoms of gold
in gold foil
nucleus of
gold atom
As only 1 in every 20 000 a
particles are repelled the
nucleus must be very small.
Size of the nucleus.
Rutherford’s model of the atom.
Tiny nucleus
containing the
positively charged
protons.
Rest of atom is mostly empty
space. The negatively charged
electrons are spinning round
the nucleus.
Review of the Rutherford's experiment
What were Rutherford’s conclusions from the Gold Foil Experiment?
 Atom has a positively charged nucleus
 electrons are outside,
 atoms are mostly empty
 Nucleus contains most of the mass.
Rutherford’s Planetary Model
• To explain his
observations, Rutherford
developed a new model
called atomic planetary
model
•The electrons orbit the
nucleus like the planets
revolve around the sun.
Atomic Theory Timeline
Scientist Information Model
James
Chadwick
Discovered that neutrons were also
located in the nucleus of an atoms
and that they contain no charge.
Neutron
s
Atomic Theory
TimelineScientist Information Model
Neils
Bohr
Concluded that electrons
are located in planet-like
orbits around the nucleus
certain energy levels.
Neils Bohr (1885-1962)
Worked in Rutherford’s lab
Wondered why – electrons are not
attracted to the + nucleus and
cluster around it
Disproved Rutherford’s Planetary
Model
Experimented with light and its
interaction with matter to develop
a new model.
Bohr’s Energy Level Model
Energy Level Model: Electrons are arranged in
circles around the nucleus. Each circle has a
different energy.
•Electrons are in constant motion, traveling
around the circle at the speed of light.
•Electrons can “jump” from one circle to the next
•But they can’t go to the nucleus they traveling
too fast to be fully attracted.
Nucleus
1st shell
2nd shell
3rd shell
How to calculate the number of
electrons in each shell?
There is a formula to calculate it, the formula is 2n^2.
For first shell the number of electron will be= 2 x 1^2 = 2 electrons
ELECTRONS IN ORBIT ABOUT
THE NUCLEUS
Atomic Structure
Bohr’s Energy Level Model
 He proposed the following:
4. The electrons must absorb or emit a fixed amount of energy
to travel between these energy levels. He also purposed the idea
of shells around.
3. The electrons orbit the nucleus at fixed energy levels.
2. Electrons can only be at certain distances from the nucleus.
1. Protons and neutrons are in the nucleus
Scientist Information Model
(Many
Scientists!)
The Modern
Atomic Theory
Electrons do not orbit the
nucleus in neat planet-like
orbits but move at high
speeds in an electron
around the nucleus.
Atomic theory timeline
Atomic TheoryChanges over time…
Symbols of the element of an atom
First idea of symbols was given by Dalton. He used some symbols as given
below.
Modern symbols
Symbols used by Dalton were very complicated to be used in a chemical
equations. Therefore modern symbols are written from their starting first, first
and second or by first and third letter
For example
(i) hydrogen, H
(ii) aluminium, Al and not AL
(iii) cobalt, Co and not CO.
What is atomic mass?
Atomic mass is the mass of an single atom. It is dependent on
mass of protons and neutrons of the atom but not on electrons
because it’s mass is negligible
Atomic mass
What is atomic number?
Atomic number is equal to number of protons in the atom of
element. The elements are arranged according to the atomic
number in the periodic table.
Atomic number
the building block ATOMS
Step 1
Use your periodic table to find
an element
Step 2
 To find The number of Protons (+ charge)
 The atomic number = number of protons
 Therefore, Kr has 36 protons
Step 3
 To find The number of Electrons (- charge)
 Remember atoms have no overall charge.
 Atoms must have an equal number of protons and
electrons
 Number of protons= number of electrons
 Therefore, Kr has 36 electrons
Step 4
To find The number of Neutrons (no charge)
Check the mass of the element
 Neutrons = atomic Mass of the element – number of Protons
Neutrons = 84 – 36
Neutrons = 48
Therefore number of neutrons are 48
conclusion
the building block ATOMS
the building block ATOMS
Gravitational Force
 The force of attraction of
objects due to their masses
 The amount of gravity
between objects depends on
their masses and the distance
between them
Electromagnetic Force
 The force that results from
the repulsion of like charges
and the attraction of opposites
 The force that holds the
electrons around the nucleus
-
+
+
+
--
Notice how the particles
with the same charge move
apart and the particles with
different charges move
together.
Strong Force
 The force that
holds the atomic
nucleus together
 The force that
counteracts the
electromagnetic
force
+
+
+
+
Notice how the electromagnetic
force causes the protons to repel
each other but, the strong force
holds them together.
-
n
Weak Force
 This force plays a key role in the
possible change of sub-atomic
particles.
 For example, a neutron can change into
a proton(+) and an electron(-)
 The force responsible for radioactive
decay.
 Radioactive decay  process in which
the nucleus of a radioactive (unstable)
atom releases nuclear radiation.
+
Notice how the original
particle changes to something
new.
the building block ATOMS
the building block ATOMS

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the building block ATOMS

  • 4. Atomic Structure  Atoms are composed of 2 regions:  Nucleus: the center of the atom that contains the mass of the atom  Electron cloud: region that surrounds the nucleus that contains most of the space in the atom Nucleus Electron Cloud
  • 5. Three subatomic particles make up every atom: Subatomic Particle Charge Location Charge (coulombs) mass Proton Positive (+) Nucleus or “Core” +1.6 x 10-19 1.67 x 10-24 Neutron No Charge (0) Nucleus or “Core” 0 1.67 x 10-24 Electron Negative (-) Electron Cloud -1.6 x 10-19 9.1 x 10-28
  • 6. Notice the smaller particles that make up this neutron after you take a closer look. + Notice the smaller particles that make up this proton after you take a closer look.
  • 10. 4. Atoms cannot be created, divided into smaller particles, or destroyed. The law of conservation of mass **In a chemical reaction, atoms of different elements are separated, joined or rearranged. They are never changed into the atoms of another element. 5. Atoms combine in definite whole number ratios to make compounds (you can’t have a ½ of a Carbon bonding with Oxygen; it’s a whole atom or no atom) Dalton’s Atomic Theory (1803)
  • 11. Atomic Theory TimelineScientist Information Model John Dalton All matter is made of atoms. Atoms are too small to see, indivisible and indestructible. All atoms of a given element are identical. And are not further divisible.
  • 12. John Dalton (1766-1844) • Dalton is the “Father of Atomic Theory” • John Dalton was first modern scientist to give the concept of atom • Dalton’s ideas were so brilliant that they have remained essentially intact up to the present time and has only been slightly corrected.
  • 13. Atomic Theory TimelineScientist Information Model J.J Thompson Discovered the negative electron, and predicted that there also must be a positive particle to hold the electrons in place.
  • 14. JJ Thomson (1856-1940) • Used cathode rays to prove that Dalton’s Solid- ball model could be broken into smaller particles •Thomson is credited with discovering electrons
  • 15. Thomson’s Plum Pudding Model •Thomson’s Plum Pudding model is a + charge sphere that has (- )charged electrons scattered inside, like “raisins” in “plum pudding”. •Overall, the atom is neutral atom because the atom had the same number of positive and negative charges. •From Thomson’s experiments, scientists concluded that atoms were not just neutral spheres, but somehow were composed of electrically charged particles.
  • 16. Atomic Theory TimelineScientist Information Model Ernest Rutherford Discovered the nucleus of an and named the positive particles in the nucleus “protons”. Concluded that electrons are scattered in empty space around the nucleus.
  • 17. Ernest Rutherford (1871-1937) Learned physics in J.J. Thomson’ lab. Noticed that ‘alpha’ particles were sometime deflected by something in the air. Gold-foil experiment
  • 18. Rutherford’s alpha scattering experiment. source of alpha particles thin gold foil photographic film beam of a particles most pass straight through 1 in 20 000 deflected
  • 19. Rutherford’s explanation. atoms of gold in gold foil Path of an a particle nucleus of gold atom All these a particles pass straight through the empty space that makes up most of the atom. This a particle passes close enough to nucleus to be repelled As a particles are positively charged, the nucleus must contain positively charged protons.
  • 20. atoms of gold in gold foil nucleus of gold atom As only 1 in every 20 000 a particles are repelled the nucleus must be very small. Size of the nucleus.
  • 21. Rutherford’s model of the atom. Tiny nucleus containing the positively charged protons. Rest of atom is mostly empty space. The negatively charged electrons are spinning round the nucleus.
  • 22. Review of the Rutherford's experiment What were Rutherford’s conclusions from the Gold Foil Experiment?  Atom has a positively charged nucleus  electrons are outside,  atoms are mostly empty  Nucleus contains most of the mass.
  • 23. Rutherford’s Planetary Model • To explain his observations, Rutherford developed a new model called atomic planetary model •The electrons orbit the nucleus like the planets revolve around the sun.
  • 24. Atomic Theory Timeline Scientist Information Model James Chadwick Discovered that neutrons were also located in the nucleus of an atoms and that they contain no charge. Neutron s
  • 25. Atomic Theory TimelineScientist Information Model Neils Bohr Concluded that electrons are located in planet-like orbits around the nucleus certain energy levels.
  • 26. Neils Bohr (1885-1962) Worked in Rutherford’s lab Wondered why – electrons are not attracted to the + nucleus and cluster around it Disproved Rutherford’s Planetary Model Experimented with light and its interaction with matter to develop a new model.
  • 27. Bohr’s Energy Level Model Energy Level Model: Electrons are arranged in circles around the nucleus. Each circle has a different energy. •Electrons are in constant motion, traveling around the circle at the speed of light. •Electrons can “jump” from one circle to the next •But they can’t go to the nucleus they traveling too fast to be fully attracted.
  • 29. How to calculate the number of electrons in each shell? There is a formula to calculate it, the formula is 2n^2. For first shell the number of electron will be= 2 x 1^2 = 2 electrons
  • 30. ELECTRONS IN ORBIT ABOUT THE NUCLEUS
  • 32. Bohr’s Energy Level Model  He proposed the following: 4. The electrons must absorb or emit a fixed amount of energy to travel between these energy levels. He also purposed the idea of shells around. 3. The electrons orbit the nucleus at fixed energy levels. 2. Electrons can only be at certain distances from the nucleus. 1. Protons and neutrons are in the nucleus
  • 33. Scientist Information Model (Many Scientists!) The Modern Atomic Theory Electrons do not orbit the nucleus in neat planet-like orbits but move at high speeds in an electron around the nucleus. Atomic theory timeline
  • 35. Symbols of the element of an atom First idea of symbols was given by Dalton. He used some symbols as given below.
  • 36. Modern symbols Symbols used by Dalton were very complicated to be used in a chemical equations. Therefore modern symbols are written from their starting first, first and second or by first and third letter For example (i) hydrogen, H (ii) aluminium, Al and not AL (iii) cobalt, Co and not CO.
  • 37. What is atomic mass? Atomic mass is the mass of an single atom. It is dependent on mass of protons and neutrons of the atom but not on electrons because it’s mass is negligible Atomic mass
  • 38. What is atomic number? Atomic number is equal to number of protons in the atom of element. The elements are arranged according to the atomic number in the periodic table. Atomic number
  • 40. Step 1 Use your periodic table to find an element
  • 41. Step 2  To find The number of Protons (+ charge)  The atomic number = number of protons  Therefore, Kr has 36 protons
  • 42. Step 3  To find The number of Electrons (- charge)  Remember atoms have no overall charge.  Atoms must have an equal number of protons and electrons  Number of protons= number of electrons  Therefore, Kr has 36 electrons
  • 43. Step 4 To find The number of Neutrons (no charge) Check the mass of the element  Neutrons = atomic Mass of the element – number of Protons Neutrons = 84 – 36 Neutrons = 48 Therefore number of neutrons are 48
  • 47. Gravitational Force  The force of attraction of objects due to their masses  The amount of gravity between objects depends on their masses and the distance between them
  • 48. Electromagnetic Force  The force that results from the repulsion of like charges and the attraction of opposites  The force that holds the electrons around the nucleus - + + + -- Notice how the particles with the same charge move apart and the particles with different charges move together.
  • 49. Strong Force  The force that holds the atomic nucleus together  The force that counteracts the electromagnetic force + + + + Notice how the electromagnetic force causes the protons to repel each other but, the strong force holds them together.
  • 50. - n Weak Force  This force plays a key role in the possible change of sub-atomic particles.  For example, a neutron can change into a proton(+) and an electron(-)  The force responsible for radioactive decay.  Radioactive decay  process in which the nucleus of a radioactive (unstable) atom releases nuclear radiation. + Notice how the original particle changes to something new.