Download Atomic structure - Swampscott Middle School

Atomic Structure
What makes one element different from another ?
....every element is made of its own special atoms.
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-
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+ + +
+ +
+
+
+
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Electrons (-)
orbit the
nucleus
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Nucleus :
Protons (+)
and
Neutrons
What makes ATOMS different from another ?
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The atom is held together by forces. What is a force? __________________________________
One of the forces holding the atom together is magnetic force between the protons and electrons.
• The protons have a positive charge which pulls on the negative charged electrons .
• Likewise the negative charged electrons pull on the positive charged protons .
(opposite charges attract....like charges repel ...push each other away)
IN AN ATOM THE CHARGES ARE BALANCED... THE NUMBER OF PROTONS
IS EQUAL TO THE NUMBER OF ELECTRONS.
• So what holds the nucleus together???..... protons will repel one another...like charges repel.
the answer is the neutrons which exert a pull which holds the protons together.
The more protons in the nucleus, the more neutrons are needed to hold the nucleus together.
For example, a big atom like Uranium has 92 protons and 146 neutrons .
How do you describe the size and structure of an atom ?
...... go to the periodic table..... p.662-663 in your text.
Example : Zinc
30
Zn
65.39
Zinc
Atomic Number: Tells you the number of
protons so it also tells you the number of
electrons.
( number of protons = number of electrons )
Atomic Mass: Tells you the total number
of protons and neutrons...
(round it off to nearest whole number)
In summary... Zinc has 30 protons, 35 neutrons, and 30 electrons
65 total...Atomic Mass