2. Atom
The word atom means indivisible.
Indivisible means it can't be broken down into
more things. Why not?
Is this true for atoms?
3. John Dalton
John Dalton was a British schoolteacher.
He said that atoms:
1. Everything is made of atoms.
2. Atoms of the same element are exactly alike,
and atoms of different elements are different.
3. Atoms join with different atoms to make new
substances.
4. J .J . Thomson
J. J. Thomson was another British
scientist. In 1887 he discovered
electrons.
Image/s: wikipedia
5. Plum Pudding Model
J J Thompson
suggested that
electrons were
mixed up in the
atoms like raisins in
a 'plum pudding'.
Image/s: wikipedia
6. Earnest Rutherford
Earnest Rutherford was a New Zealander. His
famous 'gold foil' experiment showed that atoms
must have a dense core.
Rutherford's Conclusions:
1. The atom is mostly empty space.
2. There is a small, dense, nucleus at the centre of
the atom.
If an atom was the size of a sports stadium, then
the nucleus (protons and neutrons) would be the
size of a pinhead in the centre, and the electrons
would be orbiting around the outside of the
stadium.
7. Rutherford's Conclusions
1. The atom is mostly empty space.
2. There is a small, dense, nucleus at the centre of
the atom.
8. Bohr's Model
Bohr (Danish) improved Rutherford's
Model by discovering that there are
energy levels (called “electron
shells”) for electrons.
Electrons can only be at set energy
levels. Each energy level holds a
maximum number of electrons.
They are like rungs on a ladder.
9. Elements
The number of protons is called the atomic
number.
The atomic number tells us which element it
belongs to.
All the elements can be arranged by atomic
number in the periodic table. Which elements are
these?
10. The Nucleus
Each particle in the nucleus has mass of 1
Atomic Mass Unit (amu).
The mass number is the number of protons +
the number of neutrons.
11. Electrons
8A not done
Atoms are neutral if they have the same number of
electrons as protons.
At om can l ose or gain el ect r ons t o becom ions.
s e
If an at oml oses el ect r on/s, it becom a es
_ _ _ _ _ _ _ _ _ _ _ ion because it has m e or
_ _ _ _ _ _ _ t han _ _ _ _ _ _ _ _ _ .
If an at omgains el ect r ons, it becom a es
_ _ _ _ _ _ _ _ _ ion because it has m e or
_ _ _ _ _ _ _ t han _ _ _ _ _ _ _ _ .
12. Electron Shells
Electrons orbit the nucleus in shells. They always
fill the inside shell first.
The first shell can contain up to 2 electrons.
The second shell can contain up to 8 electrons.
The third shell can contain up to 8 electrons.
The fourth shell can have up to 18 electrons.
13. Isotopes
All atoms have the same atomic number, which is the number
of _________.
Atoms of the same element can have a different number of
neutrons.
1. Are their atomic numbers the same?
2. Are their mass numbers the same?
14. Animation
Make as many stable isotopes as possible, and record
them in the table: Start at the top of a page.
Element Name Atomic Number Mass Number Nuclide Symbol
15. What is an Isotope
Isotopes are atoms with the same number of
protons but different numbers of neutrons.
Since they have the same number of protons,
they belong to the same element.
Since they have the same number of electrons,
they react the same in chemical reactions. In
nature, different isotopes are all mixed up.
However, some isotopes are radioactive (give off
radiation) and some don't.
16. Example: Iodine
Iodine has many isotopes, but
Iodine-127 is stable and most
common.
a) How many protons does it
have?
b) How many neutrons does it
have?
c) Write it as a nuclide symbol.
Iodine is needed by the thyroid,
which saves a supply of it.
However about two billion
people are deficient worldwide.
Many countries add but too
much is harmful. It is commonly http://commons.wikimedia.org/wiki/File:Salt
added to salt to prevent
17. Iodine-131
Iodine-131 is another isotope of iodine. It is
radioactive (gives off radiation). It is produced in
nuclear reactions and released only during
nuclear accidents.
Since it has the same number of electrons as
Iodine-127, the body thinks it is normal iodine,
and saves it.
There have been about 6000 cases of thyroid
cancer since the Chernobyl accident in (present
day) Russia.
It can be easily prevented by taking pills of
Iodine-127, as the body saves the Iodine-127 so it
doesn't store any of the harmful Iodine-131.
18. Uranium Isotopes
Uranium has two common isotopes:
Uranium-235, which is used for nuclear
reactors (and weapons) and
Uranium-238 is most common. Naturally
these are mixed up.
What is the difference between the
different isotopes of uranium? They
cannot be separated using chemistry.
How can they be separated?
http://en.wikipedia.org/wiki/File:Gas_centrifuge_cascade.jp
19. Animation
Make as many stable isotopes as possible, and record
them in the table: Start at the top of a page.
Element Name Atomic Number Mass Number Nuclide Symbol
1 1 1
Hydrogen 1 H
Helium 2 3,4 3
2 He , 4 He
2
Lithium 3 6,7
Beryllium 4 7, 9, 10
Boron 5 10, 11
Carbon 6 11, 12, 13, 14, 15
Nitrogen 7 13, 14, 15, 16
20. Calculating the Atomic Mass
The atomic mass number of an element is an
average.
76% of Chlorine has an atomic mass number of
35.
24% of Chlorine has an atomic mass number of
37.
What is the atomic mass number of chlorine?
21. Ions
Neutral atoms have the same number of protons as electrons.
Atoms “like” (they can't think) to be neutral. But they “prefer”
to have a full outside shell (called a valence shell).
Atoms “want” to lose or gain electrons to have a full outside
shell. For example, Lithium could either gain ____ or lose
_____ electrons.
Atoms lose or gain electrons by giving, receiving or sharing
them with other atoms. This is called bonding, and is the
basis of chemistry.
Ions are written as the element symbol with +s or -s to show
electrons gained or lost. Eg
22. Atoms and Ions
Element Electrons it “wants” Ion Symbol
to Lose or Gain
Hydrogen*
Lithium
Beryllium
Oxygen
Flourine
Argon
Additional blog note: According to what we learned, hydrogen could either gain or lose 1.
To become an ion, Hydrogen will always lose 1 to become H+.
Argon does not “want” to lose or gain any, because it already has a full valence shell.
23.
24. Questions
1. Explain what an ion is.
2. Explain what is meant by the term “valence shell”.
3. What (in terms of ions) do Hydrogen, Lithium and
Sodium all have in common?
4. What (in terms of ions) do Oxygen and Sulfur have in
common?
5. What (in terms of ions) do Argon and Neon all have in
common?
6. How many electrons does a sodium atom “want” to
gain or lose, and why? How about a chlorine atom?
7. A sodium atom meets a flourine atom and explains her
need (from Q6) and the flourine atom explains hers in
turn. What arrangement could they come to? When they
do, what have they made?
25. Periodic Table
All elements can be arranged in the periodic table
by ______________.
Rows are called periods. We will learn about them
soon.
Columns are groups. What is the same about
groups of elements?
26.
27. Grouping the Elements
A group is a column (going down) of elements.
Elements in the same group usually have the
same number of electrons in their outside shell.
Groups have similar reactivity. For example, alkali
metals are very reactive.
28. Ions
An ion is an atom which has ________ or
________ electrons in order to have a full
outer (__________) shell.
Atoms which can easily lose or gain up to
three electrons in order to have a full
________ shell can form ions.
29. Ionic Bonds
In order to become an ion, an atom needs to find
another atom to 'give' its electrons to or take them
from. A positive ion and a negative ion then form
an ionic bond, making an ionic compound.
Example: Sodium Chloride:
An excellent image of Sodium
Chloride can be found here:
http://www.school-for-champions.com/ch
30. Review
Draw atomic diagrams for magnesium-24 and
chlorine-35.
What is the ratio of magnesium atoms to chlorine
atoms for it to be balanced?
Write the name and the chemical symbol of the
ionic compound created.
Blog note: Magnesium Chloride is known as
“Nigari” in Japanese, and is used to make tofu.
An image can be found here:
http://www.moris-diet.com/kasseiion/
31. Use the Cutouts and Make Formula
for the Following:
Table salt (sodium chloride)
Lithium Fluoride
Hydrochloric Acid
(hydrogen chloride- next unit)
Magnesium Chloride
Magnesium Oxide
Aluminium Oxide
Write the chemical formula (eg MgCl2) under
each one.
Blog note: This was set for homework, and checked before Spring Break. Please make sure
you complete it if you haven't already.
32. Calcium Chloride
Calcium Chloride is a salt used to
de-ice roads in cold conditions.
1. What ions do calcium and
chlorine make? Explain why. You
may use a diagram, but you don't
have to.
2. How many of each atom will
be needed to make calcium
chloride? Explain why.
3. Write the chemical formula for
calcium chloride.
http://en.wikipedia.org/wiki/File:Calcium_chloride_CaCl2.jpg
