Science Crossword puzzle

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Across
  1. 2. A membrane bound organelle that contains genetic (DNA) material.
  2. 5. Horizontal rows on a periodic table. Tells you how many outer electron shells/energy levels an element has.
  3. 6. Positively charged particle.
  4. 7. Negatively charged particle.
  5. 10. Tells us the number of protons inside the nucleus.
  6. 12. What you breathe out. Often referred to as C02.
  7. 15. A substance that contains atoms of more then two different elements that are chemically joined together. Example: Water.
Down
  1. 1. Vertical columns on a periodic table. Tells you the number of electrons in the outer shells.
  2. 3. substances that cannot be broken down into other substances. They are made up of their own type of atom.
  3. 4. Made up of atoms that are held together by chemical bonds.
  4. 8. What you breathe in. Atomic number is 8.
  5. 9. Neutral charge particle.
  6. 11. elements symbol is Fe.
  7. 13. Building blocks of life. Neutral charge.
  8. 14. If a atom has more electrons than protons, or more protons than electrons its called a...