periodic table

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Across
  1. 4. ______ energy required to remove an electron from an isolated gaseous ion or atom at ground state
  2. 6. presented in periodic table
  3. 7. relative ability of atom to attract the bonding electrons
  4. 8. effective ______ charge increases when number of proton increases
Down
  1. 1. vertical classification of periodic table
  2. 2. electron at the last shell of atom
  3. 3. horizontal classification of periodic table
  4. 5. represented by the valence electron orbital