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The Nucleus

Middle of atom

has protons and neutrons

positive charge whole mass of atom, concentrated in nucleus 

tiny compared to rest of atom  

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The Electrons

move around nucleus

negatively charged 

tiny, cover a lot of space

volume of orbits determines size of atom

no mass

occupy shells around nucleus

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Particle, Mass and Charge

Proton Mass: 1 

Charge: +1

Neutron Mass: 1

Charge: 0

Electron Mass: very small (0)

Charge : -1

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Number of Protons Equals Number of Electrons

Neutral atoms: no charge

Charge on electrons same size as charge on protons but opposite

Number of protons equals number of electrons in neutral atom

electrons added or removes, atom is charged, then an ion 

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Atomic Number and Mass Number

atomic number: number of protons

atoms of same element, same number of protons

neutrons, minus atomic number from mass number 

mass number: biggest number

mass number maybe double proton number 

same number of protons and neutrons in nucleus 

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