Chem Class- March 5, 2010

Emission Spectra
-Each element gives off a specific colour of light
- These are known as emission spectra
             - Unique to each element
             - Astronomers make use of this to find out which elements
               a star is composed of
- If electrons absorb energy they can be bumped to a higher level
- When they fall to a lower level they release that energy as light

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Atomic Structure
- Atoms are made up of parts called subatomic particles (protons, neutrons and electrons)

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Atomic Number

- Atomic Number = number of protons

 

A = atomic number/ B = Ion charge/ C = Symbol/

D = Element name/ E = Atomic Mass

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Isotopes
- The nymber of protons determine the type of element
- Changing the number of neutrons changes the isotopes of the element
- All isotopes have the same chemical properties

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Mass Number

- Mass number is the total of protons and neutrons

- Symbol given is A

- Different isotopes have different masses

- Mass number = atomic number + number of neutrons

A = Z + N

Let's say you're given the Isotope of 54-Fe. The mass would be 54, the atomic number would stay the same as it is given in the periodic table (26), the number of protons would be 26 (same as the atomic number) and the number of neutrons would be 28 (mass number - atomic number).

Try 14-C
Mass = 14/ Atomic number = 6/ Number of protons = 5/ Number of neutrons = 8


Here's a video on Isotopes as well as the Atomic Mass: