4. Atomic number is determined by the number of 5. The left to right order of elements in the periodic table is based on their 6. Atoms are electrically neutral because 7. Atomic mass of an atom is determined by the number of 8. Which is the only subatomic particle that differs in isotopes. 9. What are radioactive isotopes and their uses? 10. Which is the only subatomic particle that is directly involved in the chemical reactivity ? 11. How does the potential energy of electrons in valence shells different from inner shells? 12. What is the valence of Nitrogen How many bonds can it form 13. Why do ,Li and 11Na exhibit similar chemical behavior? What is their electron configuration: 14. Definition -Molecule, Compound – H2O 15. Why is Helium chemically inert 16. High electronegativi 17. Explain difference between lonic & Covalent bonds: ity difference between two atoms gives rise to what type of bond: How many protons and electron in Li+ ; How many protons and electron in C 18. Explain Li+: Cl-: 19 What type of bond is seen in LiCI: 20. What type of bond is seen in 02? Explain what this means. 21. Explain the difference between a nonpolar covalent bond and a polar covalent bond. 22. What type of bond is seen in water molecule: 23. Place these bonds in order from the strongest to the weakest: hydrogen bonds, covalent bonds, ionic bonds.