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Chapter 4

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Chapter 4

- Are parts of matter that make up atoms.
- protons, electrons, and neutrons

Particle

Symbol

Charge

Mass

Proton

p+

1+

1

Neutron

n

0

1

Electron

e-

1-

- Is the number of protons in an atom.
- all atoms of an element have the same number of protons
- Each element has a unique atomic number

- the number of protons is equal to the number of electrons
- the charges balance

- is the total number of protons plus neutrons.
- For example Oxygen contains 8 protons and 8 neutrons so its mass number is 16
- to find the number of neutrons subtract the number atomic number from the mass number.
- number of neutrons = mass number - atomic number.

- gold has a atomic number of 79 and a mass number of 197.
- number of neutrons = mass number - atomic number
- number of neutrons = 197 – 79
- number of neutrons = 118

- are atoms of the same element with different numbers of neutrons.
- isotopes have different mass numbers
- to distinguish isotopes, isotopes are referred to by there mass numbers
- Example Oxygen-16 and Oxygen-17
- Oxygen-16 has 8 p+ and 8 n
- Oxygen-17 has 8 p+ and 9 n

- Section 4.2 work sheet
- Read section 4.3 page 113 - 118