Atoms and Radioactivity

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Across
  1. 2. A tabular array of the chemical elements organised by atomic number
  2. 3. Each of more than one hundred substances that can't be chemically interconverted or broken down
  3. 6. A group of atoms bonded together representing the smallest fundamental unit of chemical compound that can take part in a chemical reaction
  4. 8. An unstable form of a chemical element that releases radiation as it breaks down and becomes stable
  5. 9. Electromagnetic radiation that is emitted by an unstable nucleus of an atom during radioactive decay
  6. 13. When two light atomic nuclei combine to form a single heavier one while releasing a lot of energy
  7. 15. A subatomic particle that is found in all atoms
  8. 16. Each of 2 or more forms of the same element that contains equal numbers of protons but different amount of nucleaus
  9. 17. When an unstable atomic nucleus loses energy by radiation
  10. 19. A subatomic particle of about the same mass as a proton but without an electrical charge
Down
  1. 1. The time taken for the radioactivity of a specified isotrope to fall to half its original value
  2. 4. The association of atoms or ions to form molecules, crystals and other structures
  3. 5. A stable subatomic particle in atoms with a positive electrical charge
  4. 7. The transmutation of a neutron into a proton and an electron
  5. 10. Consist of two protons and two neutrons bound together into a particle identical
  6. 11. a substance made of 2 or more elements chemically bonded in a fixed ratio
  7. 12. The emissions of energy as electromagnetic waves or as moving subatonic particles, espeically high-energy particles which cause ionisation.
  8. 13. A subdivison of a heavy atomic nucleus, such as that of uranium and plutomium
  9. 14. The small dense region consisting of protons and neutrons at the centre of the atom
  10. 18. The basic building block of matter