notes from revision guide

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structure of atoms:

the nucleus is in the middle of the atom-it contains protons and neautrons-overall positive charge-whole mass is concentrated in the nucleus-tiny compared to atom.

the electrons move around the nucleus- negative charge- tiny compare to nucleus-size of orbit determins how big they are- virtually no mass- occupy shells around nucleus.

the number of protons is equal to the number of electrons as neutral atoms have no charge- but the charge of the electrons is the same size as the charge on protons but opposite- number of protons is always equal to number of electrons in an atom- the number of neutrons isn't fixed but about the same as the number of protons.

know your particals:

protons are heavy and positivly charged

neutrons are heavy and neutral

electrons are tiny and negitivley charged

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electron shells

electron shell rules: electrons always occupt shells- lowest energy levels are always filled first- 1st shell: 2 2nd shell:8 3rd shell:8- happier when they have full electron shells- in most atoms the outer shell is not full this makes them want to react

electronic configuration e.g 2,8,8 for argon

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elements consist of one type of atom only!          examples of elements are copper, aluminium, iron, oxygen and nitrogen- each element has a different number of protons- each element has an atomic number= tells you the number of protons and electrons  in the atom (small number) and a mass number = tells you the total number of protons and neutrons in the atom (big number)

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isotopes and relative atomic mass

isotopes are different atomic forms of the same element, which have the same number of protons but different number of neutrons!  e.g carbon 12 and carbon 14 they also have different mass numbers

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