Predict a simple reaction from the outer electrons

Answer Key - Grade 10 Science Worksheet - Challenge Me

Circle the best answer, or write your answer on the line.

1. 1.

   Ari reacts 8 aluminum atoms (group 13) with oxygen gas (group 16). Electrons lost must equal electrons gained. How many O₂ molecules are used?

   6 molecules
2. 2.

   Bo reacts 12 magnesium atoms (group 2) with nitrogen gas (group 15). Electrons lost must equal electrons gained. How many N₂ molecules are used?

   4 molecules
3. 3.

   Esme reacts 12 lithium atoms (group 1) with oxygen gas (group 16). Electrons lost must equal electrons gained. How many O₂ molecules are used?

   3 molecules
4. 4.

   X is a main-group metal that forms X₂O₃ with oxygen. Which group is X in, Jun?

   • Group 15, since each X atom gains 3 electrons
   • Group 2, since each X atom loses 2 electrons
   • Group 13, since each X atom loses 3 electrons

5. Read this first

   Magnesium reacting with nitrogen (example data)

   measurement	value
   magnesium used (g)	1.215
   product formed (g)	1.683
   magnesium molar mass (g/mol)	24.3
   nitrogen molar mass (g/mol)	14.0

6. 5.

   Using the table, which formula does the product have, Luz?

   • MgN: one magnesium atom pairs with one nitrogen atom
   • Mg₂N₃: the mole ratio of Mg to N is 2 to 3
   • Mg₃N₂: 0.0500 mol of Mg to 0.0334 mol of N is 3 to 2
7. 6.

   A student says nitrogen has 5 outer electrons, so it forms N⁵⁺. Which reply fits, Milo?

   • Supported: nitrogen is a nonmetal, and nonmetals lose their outer electrons
   • Not supported: nitrogen reaches a full shell by gaining 3 electrons, forming N³⁻
   • Supported: an atom's charge matches its number of outer electrons, as with sodium

8. Sodium reacting with chlorine (example data)

   measurement	value
   sodium used (g)	2.30
   chlorine used (g)	3.55
   sodium molar mass (g/mol)	23.0
   chlorine molar mass (g/mol)	35.5

9. 7.

   A student says the masses 2.30 and 3.55 are about 2 to 3, so the formula is Na₂Cl₃. Which reply fits the table, Pia?

   • Not supported: masses cannot help, so no formula can be found from these data
   • Supported: masses show how many atoms combine in the formula, so 2 to 3 is the ratio
   • Not supported: in moles it is 0.100 Na to 0.100 Cl, a 1 to 1 ratio, so NaCl

10. Element A ionization energies (real data, rounded)

    step	energy (kJ/mol)
    first	496
    second	4,562
    third	6,910

11. 8.

    Using the table, how many outer electrons does element A have, Ren?

    • 3: three energies are listed, so three electrons can be removed
    • 1: the energy jumps from 496 to 4,562 after the first electron
    • 2: the energy rises by about 4,000, which counts two electrons

12. Element B ionization energies (real data, rounded)

    step	energy (kJ/mol)
    first	738
    second	1,451
    third	7,733

13. 9.

    Element B is a metal. Using the table, which formula does it form with chlorine, Tala?

    • BCl₂, since the big jump comes after the second electron
    • BCl₃, since three energies are listed
    • BCl, since the first electron comes off most easily

14. Elements B and D ionization energies (real data, rounded)

    step	element B (kJ/mol)	element D (kJ/mol)
    first	738	578
    second	1,451	1,817
    third	7,733	2,745
    fourth	not listed	11,577

15. 10.

    Which element, B or D, is more likely to form a 3+ ion, Zee?

    • D: energies rise gently through the third electron, then jump at the fourth
    • Both: each table lists a third energy, so each can lose three electrons
    • B: its third energy, 7,733, is the largest in the table and so the most telling