crossword puzzle

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Across
  1. 4. a positive electric charge equal in magnitude to that of an electron, but of opposite sign.
  2. 8. electrically neutral group of two or more atoms held together by chemical bonds.
  3. 9. table of elements It is widely used in chemistry, physics, and other sciences.
  4. 11. the same mass as a proton but without an electric charge.
Down
  1. 1. Every atom will have the same number of
  2. 2. a group is a column of elements in the periodic table.
  3. 3. The basic unit of a chemical element.
  4. 5. a part or aspect of something abstract, especially one that is essential or characteristic.
  5. 6. molecules composed of atoms from more than one element held together by chemical bonds.
  6. 7. number proton number of a chemical element is the number of protons found in the nucleus of every atom of that element.
  7. 10. Periodic table is a row of chemical elements.