What will we cover today?

• What you should remember from last week

• How the PT is structured

• How to read information from the PT

• How to determine the subatomic particle numbers of a particular element

The Periodic Table

• Mendeleev is the scientist credited with developing the majority of the PT - he did so through deduction and reasoning

• He predicted the existence of elements that weren't even discovered yet through their properties (mass, density, melting point etc.)

Modern Periodic Table

• 118 elements - 94 natural

• Can sort it into metals, non-metals, and metalloids (+ many more families, but we don't need to know them!)

• Sorted into groups (down) and periods (across)

• Each element has an atomic number (goes up by 1), atomic mass, name, and symbol

​Determining subatomic particles

• Protons = atomic number

• Electrons (in an neutral atom) = atomic number

  • in an ion = number of electrons when the atom has a full outer shell

• Neutrons = mass number - atomic number

​Isotopes

​Isotopes are different forms of a particular atom.

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Different isotopes have different numbers of neutrons in their nucleus, but have the same number of protons

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The number = the mass ​

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Often have different physical properties ​

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