chemistry atomic structure

• isotopes are atoms that have the same number of protons (atomic) but have a different number of neutrons(mass)
• The word 'relative' is used because the mass of all atoms is measured relative to the mass of an atom of carbon-12
• atoms have the same number of protons as electrons
• An element contains only one type of atom that cannot be broken down into simpler substances by chemical means
• a compound is two or more different elements chemically combined
• Thompson discovered the electron
• Rutherford discovered the protons
• Chadwick discovered the neutrons
• the radius of an atom is 1x10^-10m
• the radius of a nucleus 1x10^-14m
• and electron has a mass of 1/1840 and is located in the shell
• outer shell is sometimes called a valence shell
• An ion is a charged particle formed whenever an atom loses or gains electrons to achieve a full outer shell
• metals lose electrons and form cations+
• nonmetals gain electrons and form anions-
• group one has 1 outer electon

  group two has two outer electrons..

  therefore group one has a 1+ charge on their ions and group 2 has 2+
• isotopes are atoms that have the same atomic number and different mass numbers. isotopes have the same chemical properties
• to find RAM of lithium 6Li 7% and 7Li 93%

  Ar=(6*0.07)+(7*0.93)= 6.9
• a nanometre is 10^—9m.
• 1,000,000,000nm=1 metre
• 1000pm is 1nm
• 1000fm is 1pm therefore 1fm is 1x10^-15m
• diatomic elements are:

  H2

  N2

  O2

  F2

  Cl2

  Br2

  I2
• some examples of compounds are:

  H2O

  NaCl

  CO2
• an oxide ion is 02-

  config is 2,8

  8 protons and 10 electrons as the ion has gained 2 electrons to fill the outershell (hence 2- charge)
• plum pudding model is a positive sphere with electrons embedded inside