The Atom

What’s Inside an Atom? An atom is made up of a team of three players: protons, neutrons, and electrons They each have a charge, mass, and a location Protons + Neutrons collectively called nucleons

What is the structure of an atom? Nucleus – center of the atom –Home of Protons and Neutrons –Proton Has a positive (+) charge Has a relative mass of 1 Determines the atomic number Found inside the nucleus

What is the structure of an atom? –Neutron Has no charge (0) Has a relative mass of 1 Determines the isotope –Isotopes are two of the same element with different masses Found inside the nucleus

What is the structure of an atom? Electron –Has a negative (-) charge –Has a relative mass of 0 (zero) –Determines the ion –Found outside the nucleus

Electrons circle around the nucleus of an atom. Protons are a main part of the nucleus of an atom. Neutrons also hang out in the nucleus of an atom.

Electrons have a negative charge.  Protons have a positive charge. + Neutrons have no charge. 0

Electrons are little and have a mass of almost zero. Protons are big and have a mass of one. Neutrons are also big and have a mass of one.

How are P, N, e - related? # protons = atomic number = Z # electrons = # protons in a neutral atom # protons + # neutrons = mass number = A –Ex: The atomic number of Hydrogen (H) is 1, so all hydrogen atoms have 1 proton. –Ex: All Oxygen atoms (O) have 8 protons, so the atomic number of Oxygen is 8. Remember all atoms are electrically neutral. Therefore; the number of Protons equal the number of Electrons. Meaning the number of negatively charged particles must equal the number of postively charged particles. –Ex: Helium (He) has 2 protons and 2 neutrons: its mass number is 4. –Ex: Carbon (C) has 6 protons and 6 neutrons: its mass number is12.

A X ZN # protons + # neutrons = mass number = A # protons = atomic number = Z # neutrons Structure of the Nucleus

A Al Structure of the Nucleus

The ratio of the number of neutrons to the number of protons N/Z is an approimate index of the stability of a nuclide. N/Z = 1 in the stable nuclei with low atomic no. Ex, C 6 12 Structure of the Nucleus

Nomenclature Isotopes: Nuclides of the same atomic number. O O O Isotones: Nuclides having the same number of neutrons but different atomic number Fe Co Cu Isobars: Nuclides with the same no. of nucleons that is the same mass no. but different no. of protons Cu Zn Isomers: Nuclides having the same number of protons and neutrons but differing in energy states and spins. 99Tc 99mTc

Units of Radioactivity 1 curie (Ci) = 3.7 X dps = 2.22 X dpm 1 millicurie (µCi) = 3.7 X 10 7 dps = 2.22 X 10 9 dpm 1 microcurie (µCi) = 3.7 X 10 4 dps = 2.22 X 10 6 dpm

1 Becquerel (Bq)= 1 dps = 2.7 X Curie 1 kilobecquerel (Bq)= 2.7 X Curie 1 Ci = 3.7 X Becquerel (Bq) Units of Radioactivity

Decay Equations -dN/dt=YN –Y Lambda= decay constant. –Defined as the probability of disintegration per unit time for the radioactive atom –-dN/dt = A =disintegration rate –N is the no. of radioactive atoms At = Aoe -yt A=yN Y=0693/t1/2 –t1/2 = the time required to reduce the intial activity of a radionuclide to one half

Problems 1.At 11:00 A.M., the 99mTc readioactivity was measured as 9 mCi on a certain day. What was the activity at 8:00 A.M. and 4:00 P.M. on he same day (t1/2 of 99mTc= 6hr)

Thank You “Instead of giving yourself reasons why you can’t, give yourself reasons why you can”