Sub-Atomic Particles 18/1/13

Sub-atomic Particles

• Protons
• Electrons
• Neutrons

All types and sizes of atoms consist of the same type of sub-atomic particles but of different numbers.

• Sub atomic particles CANNOT be used to identify/ distinguish elements. -->  All elements have the same type of sub-atomic particles

STRUCTURE OF AN ATOM

Proton:                                    

Carries a charge of +1

Relative mass of 1

Found in the nucleus -> centre of atom

Symbol : p

Neutron:

Carries no charge = 0

Relative mass of 1

Found in the nucleus -> centre of atom ( together with proton ^)

Symbol : n

Electron:

Carries a charge of -1

Negligible mass of 1/1840

Found in shells which surround the atom

Symbol : e

Relative Mass:

• Particles in atoms are VERY LIGHT
• proton weighs about 1.67x10^-27kg
• Hence scientists measure massess of atom against standard unit called atomic unti mass (anu)
• 1 amu = 1.67x10^-27kg  , which is also known as relative mass 
• When you say relative mass of 1, dont put units. ( SAME THING)

• All atoms are electrically neutral. ( negative charge of electron and positive charge of proton)
• An atom contains an equal number of proton and electron

Proton and Nucleon Number:

• Number of proton = proton number --> used to arrange elements in periodic table  
• ^ ALSO KNOWN AS THE ATOMIC NUMBER
• symbol = Z
• tell us the number of electrons in the atoms too!

Example: Proton number of nitrogen is 7

   A nitrogen atom has seven protons and seven electrons.

Different atoms have different proton number

each element has a unique proton number! -> only thing thats different from element to element

• Atoms of different elements have different numbers of protons.

Example: Carbon has a proton number of 6. 

Any atom with 6 protons must be a carbon atom

Nucleon Number:

Also known as the mass number.

• The mas of an atom depends on the number of protons and neutrons in an atom.
• Electron's mass = negligible!
• Symbol = A
• Nucleon Number = number of protons = neutrons

!! Nucleon Number and Mass number DO NOT mean the same thing, but coincidentally, the value is the same.

Representing Proton and Nucleon number:

An element can also be represented using only the nucleon number:

    e.g.: sodium-23 or 23-NA

Biography of Scientist who made notable contributions to the world of atoms:

Read up articles about:

John Dalton

Ernest Rutherford

George Johnstone Stoney

Dmitri Mendeleev

:>