Download Subatomic Particles

Subatomic Particles
Electron
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-ve charged particle
Outside of nucleus
Thomson’s discovery
Mass = 9.11 x 10-28g
Charge = -1.76 x 108C (coulombs)
Proton
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+ve charged particle
Inside nucleus
Rutherford’s discovery
Mass = 1.67 x 10-24g (1836x heavier than
electron)
• Charge = +1.76 x 108C (opposite electron)
Neutron
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No charge
Inside nucleus
Chadwick’s Discovery
Mass of neutron = 1.67 x 10-24g (same as
proton)
• Charge = no charge
Atomic Number
• This is the number of protons in an atom
• Hydrogen has 1 proton and thus is atomic
number 1
• Oxygen has 8 protons and thus atomic number 8
• Every element is different due to its different
numbers of protons
• So changing the number of protons changes the
element!
– Some elements may have the same electrons (ions) or
the same neutrons (isotopes)
Atomic Number
• The atomic number is found on the bottom
left corner
• Atomic mass on the top left corner
• Symbol in the middle
Atomic Number
• Electrons counterbalance the charge of protons
– So the number of electrons in a neutral atom is the
same as the number of protons
• When an electron is removed from a neutral
atom
– It becomes +ve because #protons > #electrons
• When electron is added to a neutral atom
– It becomes –ve as #protons < #electrons
• Atoms with net charges are called ions
– Net charge = #proton - #electron
Atomic Number
• We show an ion exist by putting a +/- number
on the top right corner of our element
• NOTE! – Proton numbers do not change in
ions
Atomic Number
• You try! Find the number of protons and
electrons of the following
– Uranium
– Thallium
– Tin
– Lead
– Mercury
– Helium
– Yttrium
Atomic Mass
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The mass of the atom
Atomic mass = #neutron + #protons
#neutron = atomic mass – atomic number
Oxygen has an atomic mass of 16. It has an
atomic number of 8. To find the #neutron, we
subtract the two.
– 16-8 = 8 neutrons
• Gold’s atomic mass is 197 and atomic number is
79
– #neutron = 197 – 79 = 118 neutrons
Atomic Mass
• The electron is so light, it is only 1/1836 the
mass of a proton and neutron that it does not
contribute to the mass of the atom
• We base all our atomic masses on the mass of
carbon-12. The 12 stands for its atomic mass
of 12.0000g/mol or amu (atomic mass unit)
• 1 amu = 1.67 x 10-24g or the same mass as a
neutron and proton
Atomic Mass
• You try, find the number of neutrons of the
following. As well, what is the number of
protons and electrons?
– Plutonium
– Einsteinium
– Thorium
– Gallium
– Germanium
– Californium
Practice time!
Isotopes
• As with ions, which is when we have different
numbers of electrons
• An isotope is where the number of neutron is
different
• Isotopes still have the same number of
protons as the original atom
• As they have different atomic masses due to
the different number of neutrons, we write
their names different.
Isotopes
• We write the names with a hyphen and their
mass
• Carbon-12 = regular 12 amu carbon
• Carbon-13 = carbon with 1 extra neutron
• Carbon-14 = carbon with 2 extra neutrons
Isotopes
• When writing them in chemical symbol
format, we drop the atomic number and just
write the mass
• 16O and 18O
• 35Cl and 37Cl
Isotopes
• Lets take a look at hydrogen and its isotopes
• Hydrogen-1 (protium)
– 99.985% of all hydrogen atoms
– Most common element in our universe
– Has 1 proton and o neutrons
• Hydrogen-2 (deuterium)
– Has 1 proton and 1 neutron
– 0.0167% of all hydrogen atoms
– Used in nuclear reactors as heavy water D2O
• Hydrogen-3 (tritium)
– Has 1 proton and 2 neutrons
– Used in hydrogen bombs
Isotopes
• We can find the number of protons, neutrons,
and electrons of an isotope as we would with
a standard atom.
– Just have to note the mass and that mass change
is due to neutrons
Isotopes
• You try finding the number of protons,
neutrons, and electrons with the following
– Uranium-238
– Oxygen-18
– Xenon-126
– Hafnium-180
Average Atomic Mass
• Why are all the masses of elements not whole
numbers?
• Why isn’t carbon 12.0000 and oxygen
16.00000 and chlorine just 35.00000 or
36.00000?
• This is due to the masses in the periodic table
being averages of all the masses of the
isotopes based on abundance
Example
• Carbon-12 is 98.9% abundant in nature
• Carbon-13 is 1.1% abundant in nature
Average Atomic Mass Steps to solve
• Multiply each percentage as a decimal with
the atomic mass
• Add up all your decimals
• This is your average atomic mass that shows
up on the periodic table
Example
• Carbon-12 is 98.9% abundant in nature
• Carbon-13 is 1.1% abundant in nature
Example
• Nitrogen has an average atomic mass of
14.007. The two isotopes that make up
nitrogen are nitrogen-14 and nitrogen-15.
What are the percent abundance of each
isotope?
Average Atomic Mass
• You try
– Chlorine is 75.8% chlorine-35 and 24.2% chlorine37. What is the average atomic mass of chlorine?
Electron Arrangements
• We look at electron arrangements in the form
of Bohr models
Electron Arrangements
• Each of the noble gases outer shells are full
– They satisfy the octet rule
• Outer shell electrons are also called “valence
electrons”
– Hence why the outer shell is usually called the
valence shell
• A full outer shell is stable, it doesn’t want to
give or receive any more electrons
Remember!
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1st Shell = 2 electrons
2nd Shell = 8 electrons
3rd Shell = 8 electrons
4th Shell = 18 electrons
----------------------------------------------------------5th Shell = 18 electrons
6th shell = 32 electrons
7th shell = 32 electrons
Remember!
• You can remember this by counting across the
periodic table.
• The first row has 2 elements so 2 electrons
• The second row has 8 elements so 8 electrons
and so forth!
How do other elements gain stability?
• Other elements do not have full outer shells
as the noble gases do
• They will try to lose or gain electrons to get to
a full outer shell
How can we tell which will lose or gain
electrons?
How can we tell which will lose or gain
electrons?
Carbon stability?
Summary of element stability
Why does an element want to gain or
lose electrons anyways?
• Every element has an affinity for electrons
– Affinity = attraction
• Some elements have more affinity than others
• We measure affinity and call it
electronegativity
• The higher the electronegativity, the more the
element wants electrons
– Fluorine has the highest electronegativity
– Highest top right and weak bottom left
So how does it work?
• When two elements with differences in
electronegativity come together, the one that
is more electronegative draws the electron
away from the less electronegative element
vs
Homework
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Page 146 #13-17
Page 147 #19
Page 149 #22
Page 150 #23 and 25
Worksheet on isotopes
Worksheet on atomic number