Atomic structure by Ruth

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The atom and atomic structure 

Nuclide: atom with specific number of protons and neutrons 

Three subatomic particles: neutrons, protons and electrons 

Neutrons + Protons contained in nucleus NOT electrons 

Two regions in atom: nucleus + electron shells 

Relative mass/Relative charge for

protons: 1/ +1

neutrons: 1/ 0

electrons: 5 x 10E-4/ -1

Atomic number: number of protons in the nucleus 

Mass number: total number of protons and neutrons 

Number of neutrons = mass number - atomic number 

Isotopes: Atoms of the same element with different mass numbers: different numbers of neutrons

e.g. carbon-12, carbon-13 

Isotopes of same chemical element: identical chemical properties + different physical properties 

Unstable nuclides: emission of ionizing radiation: radioactive - radioisotopes

Types of radiation: Deflection by electric field

Alpha: low

Beta: high

Gamma: none 

During alpha + beta radioactive decay: formation of more stable isotope 

Uses of radioisotopes:

In medicine:

Iodine -131: used to treat thyroid cancer

Iodine-125: treat prostate cancer + brain tumors

Cobalt-60: very powerful gamma emitter + suppress body's immune reaction to organ transplantations

Radiotherapy: damaging DNA of cancer cells 

In archeology: 

Carbon-14: radiocarbon dating: used to date organic remains accurately for up to 100 000 years 

Positive ions: formed when


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