Year 9 Chemistry – Structure of the Atom PowerPoint
From the first slide, copy the accepted model of an atom - don’t forget to label all
the sub-atomic particles.
Atomic Number
•The atom we have just drawn is the element _________________ (He). Its
position on the periodic table is second, and it has the atomic number ________ .
•Each ______________ on the periodic table has a different atomic number.
•The _____________________ represents the number of protons an atom of a
particular element contains in its nucleus.
•The number of ___________ protons = the number of ____________ electrons.
Mass Number
•Each atom also has a mass number. The _________________ represents the
number of particles in the ________________.
•The mass number represents the number of protons + the number of neutrons.
•In actual fact the mass number includes the mass of the electrons as well, but
because their mass is so ___________________, the mass number is rounded off
to the nearest whole number.
•If an atom was the size of a football field, the nucleus would be the size of a pin
head. The mass of an atom is therefore condensed into a very small area.
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Working out how many neutrons
•We can work out the number of neutrons if we know the ________________
number and _____________________ number.
•Helium has 2 protons (atomic number) and 4 particles in the nucleus, so therefore
4 (neutrons+protons) - 2 (protons) = 2 (neutrons).
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He
How many protons, neutrons and electrons in these atoms? Write your answers
underneath.
Isotopes
An _________________ of an atom has the same number of _____________
with a different number of neutrons.
Draw the ‘Ordinary’ Hydrogen atom and the two possible isotopes.
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Carbon - 14 is radioactive and used for dating archaeological wood up to 20,000
years old. This isotope of carbon can be represented as such:
14
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C
Draw a labeled model of the Carbon – 14 isotope.
Ions
•If an atom looses and _______________it becomes a positive ion.
•If an atom gains an electron it becomes a _____________________ ion.
•An ion is an atom with a _________________ or negative charge.
Draw a diagram to show how Hydrogen can loose an electron to become H+.
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