Chemistry Nuclear Chemistry

Basics of the Atom Location in the Atom Particle Charge Mass proton 1+ in nucleus ~1 u neutron in nucleus ~1 u electron 1– orbiting nucleus ~1/2000 u a.m.u. (u): unit used to measure mass of atoms

To find net charge on an atom, consider atomic number: # of p+ 10 Ne 20.1797 -- the whole number on Periodic Table -- determines identity of atom mass number: (# of p+) + (# of n0) (Isotope mass is NOT on “the Periodic Table.”) To find net charge on an atom, consider ____ and ____. p+ e–

I 53 125 1– Complete Atomic Designation …gives precise info about an atomic particle mass # atomic # charge (if any) element symbol Goiter due to lack of iodine iodine is now added to salt I 53 125 1–

Isotopes: different varieties of an element’s atoms -- have diff. #’s of n0; thus, diff. masses -- some are radioactive; others aren’t All atoms of an element react the same, chemically. Isotope Mass p+ n0 Common Name H–1 1 1 protium H–2 2 1 1 deuterium H–3 3 1 2 tritium C–12 atoms C–14 atoms 6 p+ 6 n0 6 p+ 8 n0 stable radioactive

TRANSURANIUM ELEMENT Element of 93 or greater in the periodic table that is produced in the laboratory by induced transmutation Transmutation: conversion of an atom of one element to an atom of another element.

Radioactivity: process in which some substances spontaneously emit radiation Radioactive decay: process in which unstable nuclei spontaneously emit radiation

FUNDEMENTAL FORCES Pull strength: strongest to weakest 1 Gravity 1/137 1 x 10-6 6 x 10-39 Electromagnetic Weak Strong

FUNDEMENTAL FORCES Distance of influence: greatest to least Gravity: influence even between universes Electromagnetic: repulsive and attractive; limited distance Weak: nuclear force allows radioactivity Strong: holds protons together, shortest distance

Basic types of Nuclear Reactions Fusion: two or more nuclei get close enough to react to form new nuclei with possible extra nuclei or particles. Fission: nuclear reaction or nuclear decay process in which the atoms nucleus splits into smaller parts (nuclei).

As the number of protons increases the ratio of neutrons to protons required for stability increases.

Rewritten for Nuclear chemistry Particles we know Rewritten for Nuclear chemistry neutron 10n 11H+1 proton 11p+1 00e-1 0-1e electron

Types of particles  42He2+ Alpha Beta 0-1e  positron 0+1e

Facts about radiation ALPHA ( 42He ) Heaviest, with a speed of 16000 km/s; ~10% of light. Least penetrating, can be stopped by a sheet of paper. Impact powerful enough to dislodge 450,000 electrons from affected atoms. 3 cm of air will also stop alpha. Only emitted from heavy elements. If inhaled or ingested can result in serious cell damage. Basements in some regions need detectors to maintain safe air supply.

Facts about radiation BETA ( 0-1e ) Low mass, speed of 270000 km/s; ~90% of light. Moderately penetrating, can be stopped by a sheet of aluminum foil. 3 m of air will also stop beta. Energetic electron emitted to lower energy and stabilize an atom. encounter with a living cell, and there may be many before the beta energy is dissipated, is likely to damage some of the chemical links between the living molecules of the cell or cause some permanent genetic change in the cell nucleus POSITRON ( 0-1e ) Same as a beta particle

Facts about radiation GAMMA RADIATION ( 00g ) photon or high-energy wave no mass or charge speed of light losing ~half its energy for every 153 km stopped by a thick or dense material High energy X-ray

Facts about the emissions Magnetic field ++++++++++ 00g Container with Radiation emitter - - - - - - - - - - 42He Beta’s lack of mass give the field and increased effect. Alpha’s mass reduces the effect but its charge means greater influence of the field Gamma is not affected by the magnetic field and has no mass (photon) Magnetic field

Facts about radiation NEUTRON ( 10n ) Result of a nuclear fission Travels thousands of meters through air. Stopped by hydrogen rich materials; water or concrete. effectively stopped if blocked by a hydrogen-rich material, such as concrete or water. Not typically able to ionize an atom directly due to their lack of a charge, they are absorbed into a stable atom, thereby making it unstable and more likely to emit off ionizing radiation of another type. Neutrons are the only type of radiation that is able to turn other materials radioactive.

Balancing Nuclear Reactions Unstable Thorium-232 emit beta particle to achieve a more stable ratio of neutrons to protons 23290Th 0-1b + Pa 23291 232 = 0 + 232 90 = -1 + 91

Try this problem with an a emisson 23692U 42He + 23290 Th 236 = 4 + 232 92 = 2 + 90

Try this problem with a b emisson 146C 0-1e + N 147 14 = 0 + 14 6 = -1 + 7 The proton neutron ratio changed from radioactive carbon-14’s 1::1.3 to stable nitrogen-14’s 1::1

Radioactive Isotopes: have too many or too few n0 Nucleus attempts to attain a lower energy state by releasing extra energy as __________. radiation e.g., a- or b-particles, g rays half-life: the time needed for ½ of a radioactive sample to decay into stable matter e.g., C–14: -- half-life is 5,730 years -- decays into stable N–14

Charting Half-life information # Half-lives 1 2 3 4 5 Time Increments Mass / 2 Percents/2 100 50 25 12.5 6.25 3.12 213,000 426,000 639,000 250 125 62.5 500 31.25 effectively stopped if blocked by a hydrogen-rich material, such as concrete or water. Not typically able to ionize an atom directly due to their lack of a charge, they are absorbed into a stable atom, thereby making it unstable and more likely to emit off ionizing radiation of another type. Neutrons are the only type of radiation that is able to turn other materials radioactive. What is the half-life of 99Tc if a 500 g sample decays to 62.5 g in 639000 years

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