ATOMS

Atoms All material is made up of tiny particles called atoms. Atoms contain protons, neutrons and electrons.

Structure of an Atom (1) (2) (3)

Sub-atomic particles Sub-atomic particle Charge Mass Position Proton Neutron Electron +1 -1 About the same as a neutron About the same as a proton About 2000 times smaller than a proton or neutron In nucleus Outside nucleus

Structure of an Atom - Lithium

Structure of an Atom – Electron shells Each electron shell can only hold a certain number of electrons. The first electron shell can hold up to 2 electrons. The second electron shell can hold up to 8 electrons. The third electron shell can hold up to 8 electrons.

6 12 Atomic (proton) number – number of protons in an atom. Mass number – number of protons plus neutrons in an atom. What is the atomic number of carbon? mass number 6 12

See Electron configuration.FLA

The atomic number and mass number (and / or atomic mass) for each element is shown on the Periodic table.

PhET build-an-atom applet

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See Element properties.FLA