Physics - atomic structure and radioactivity
atomic structure
-the further the electrons , the higher the energy level
-if atom absorbs electromagnetic radiation , an electron can move from low to high
energy level - atom can now emit electromagnetic radiation and electron returns
back to lower energy level
atomic and mass number
atomic number = number of protons and electrons
neutrons=mass number - atomic number
isotopes: atoms of the same element with different number of neutrons and mass
number
plum pudding model
-an atom is a ball of positive charge with negative electrons embedded in it
-made up of no empty space
, alpha scattering experiment+nucleur model
-scientist fired positively charged alpha particles at thin gold foil
-most of them went straight through proved atoms are made up of mostly empty
space
-however some reflected back suggesting positive charged nucleus repelled alpha
particles and that the mass is concentrated in the centre
nucleur model:
-electrons orbit the nucleus on the outside of atom
-positively charged nucleus concentrated in the centre
-made up of mostly empty space
radioactivity
radioactive decay- when unstable nucleus of isotope gives out radiation -it is a
random process
• measured in Bq (bequerel) - 1Bq = 1 decay per sec
• geiger muller tube used to measure activity of radioactive source
• count rate is number of decays recorded each second by a detector
properties of alpha, gamma and beta radiation
Alpha decay causes the mass number of the nucleus to decrease by four and the
atomic number of the nucleus to decrease by two.
Beta decay causes the atomic number of the nucleus to increase by one and the mass
number remains the same.
half lives
-time taken for activity of radioactive source to fall to half of its initial level
-the shorter the half live - safer sooner as less decays + has greatest activity >
greatest dose of radiation absorbed per second
-know how to interpret half life graphs and calculations
atomic structure
-the further the electrons , the higher the energy level
-if atom absorbs electromagnetic radiation , an electron can move from low to high
energy level - atom can now emit electromagnetic radiation and electron returns
back to lower energy level
atomic and mass number
atomic number = number of protons and electrons
neutrons=mass number - atomic number
isotopes: atoms of the same element with different number of neutrons and mass
number
plum pudding model
-an atom is a ball of positive charge with negative electrons embedded in it
-made up of no empty space
, alpha scattering experiment+nucleur model
-scientist fired positively charged alpha particles at thin gold foil
-most of them went straight through proved atoms are made up of mostly empty
space
-however some reflected back suggesting positive charged nucleus repelled alpha
particles and that the mass is concentrated in the centre
nucleur model:
-electrons orbit the nucleus on the outside of atom
-positively charged nucleus concentrated in the centre
-made up of mostly empty space
radioactivity
radioactive decay- when unstable nucleus of isotope gives out radiation -it is a
random process
• measured in Bq (bequerel) - 1Bq = 1 decay per sec
• geiger muller tube used to measure activity of radioactive source
• count rate is number of decays recorded each second by a detector
properties of alpha, gamma and beta radiation
Alpha decay causes the mass number of the nucleus to decrease by four and the
atomic number of the nucleus to decrease by two.
Beta decay causes the atomic number of the nucleus to increase by one and the mass
number remains the same.
half lives
-time taken for activity of radioactive source to fall to half of its initial level
-the shorter the half live - safer sooner as less decays + has greatest activity >
greatest dose of radiation absorbed per second
-know how to interpret half life graphs and calculations
