Fundamental Particles 1.1- 1.6

Charges and Ma**es 

Proton= +1 , 1

Neutron= 0, 1

Electron= -1, 0

• Elecrtons are held in place due to electrostatic attraction to protons
• Protons + Neutrons are held together by strong nuclear forces 

       - Stronger than the forces that hold together electrons and protons 

       - Overcomes the repulsion between protons in nucleus 

• Without nuetrons to space out positive charge we could not have stable nucleus 

--> Ma** Number, Total number of protons and neutrons 

--> Atomic Number, The number of protons in the nucleus 

--> Neutrons, Ma** number - Atomic number 

Ions 

When atoms gain or lose electrons they become ions 

Gain electrons --> negative ion is formed 

Lose electrons --> Positive ion is formed 

Arrangements 

• Not all the electrons in a shell have exactly the same amount of energy 
• Shells are divided into sub shells that have slightly different energies 
• Sub shells have orbitals which can each hold up to 2 electrons 

Each orbital in a sublevel can hold a max of 2 electrons.

Rules for filling orbitals 

1. Fill up lowest energy sub levels first 

2. Fill orbitals singly at first before doubling 

3. Electrons in the same orbital must have oppositve spin 

4. Remember that 4s is filled before 3d 

--> Isotopes, Atoms with the same number of protons but different number of neutrons 

Different isotopes vary in ma** number because of different numbers of neutrons and therefore have different physical properties 

     e.g. Melting/ Boiling point, Solubility, Appearance, Density

Different isotopes of the same element react chemically in the same way

• Chemical properties are determind by electronic structure 
• Isotopes have the same number of electrons 
• So electrons configuration is the same 

Carbon dating 

• Materials that origionally came from living things can be dated by measuring the amount of carbon-14 they contain
• Carbon-14 is radioactive istope found in carbon dioxide molecules
• same amount of carbon-14 in the air for years 
• Small amount of carbon-14 in all living organisms because it enters the food chain
• ¹⁴C is constantly produced by cosmic rays hitting ¹⁴N and converting into ¹⁴C. Therefore begins to radioactively decay back to ¹⁴N so ratio of ¹⁴C and ¹²C in the atmosphere stay the same.
• On death the organism stops exchanging carbon with atmosphere 
• As time goes on the ratio decreases in the organic matter compared with the atmosphere this can be used to date…