ATOMS Atoms All material is made up of

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 +1 In nucleus Neutron 0 Electron -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.

• 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? 6 • What is the mass number of carbon? 12

See Electron configuration. FLA

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

Ph. ET build-an-atom applet

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See Element properties. FLA