Periodic Trends Quiz

Transcription

1 Periodic Trends Quiz Name: /37 Knowledge. Answer the following questions on foolscap. /6 1. Identify one key physical or chemical property that the following pairs of elements have in common. Position in the periodic table is not a property. Make sure comparisons actually involve the same factor. a) actinide elements and transuranic elements d) lanthanide metals and alkaline earth metals b) alkaline earth metals and transition metals e) non-metals and representative elements c) noble gases and halogens f) lanthanide elements and actinide elements 2. For each of the following observations, identify if the Nuclear model of the atom is able to explain the observation or if the Bohr-Rutherford model (in its pure, original form) needed? Explain your reasoning in each case. /2 a) all fireworks essentially involve exploding different metals to produce distinct colours /2 b) calcium is less reactive than potassium /1 3.a) Some textbooks refer to effective nuclear charge. What do you think this means? /1 b) Explain how it alone affects atomic size. /1 4. Consider the following atomic sizes (measured in picometers or pm): F = 72, Ar = 87 and Br = 115. Estimate the size of a Cl atom. /4 5. Using the Bohr-Rutherford model of the atom, explain why N is predicted to be the most reactive of C N Ne? /1 6.a) Using the Bohr-Rutherford model of the atom, predict which element would have the most negative electron affinity: Hf, Ti or Zr? /4 b) Using the Bohr-Rutherford model, fully explain your reasoning. 7. For each of the following only use the Bohr-Rutherford model of the atom to: /4 a) predict the atom that would have the lowest fourth ionization energy. Al Si Ga Ge /4 b) predict the atom that would be the smallest (+) electron affinity. Be O Se Kr c) Using the Bohr-Rutherford model, fully explain your reasoning for each of the above. /1 8.a) How does the size of a Ni 2+ ion compare to a Ni atom. /3 b) Only use the Bohr-Rutherford model of the atom to explain your reasoning. /2 9. An atom has the following successive ionization energies. In which family of the periodic table does this atom belong? Show your work for any marks. I.E. kj/mol I.E I.E I.E I.E I.E /1 10. Which of the following elements is most likely to gain an electron during a chemical reaction? Mg Si B O /4 Communication. Answer the following questions on foolscap. /4 11. Draw the Bohr-Rutherford atom for 50 7 Cl.

2 Periodic Trends Quiz Name: /37 Knowledge. Answer the following questions on foolscap. /6 1. Identify one key physical or chemical property that the following pairs of elements have in common. Position in the periodic table is not a property. Make sure comparisons actually involve the same factor. a) actinide elements and transuranic elements d) lanthanide metals and alkaline earth metals b) alkaline earth metals and transition metals e) non-metals and representative elements c) noble gases and halogens f) lanthanide elements and actinide elements they both: a) have same amount of levels of electrons resulting in same amount of electron-electron repulsion between levels or are typically radioactive or have a very high number of protons or have a large atomic mass or typically react by losing electrons b) can form oxides or can react with hydrogen donors (water/acid) to release hydrogen gas or conduct electricity or typically react by losing electrons c) have a high first ionization energy or may be gases at SATP d) are actually earth metals or are solid at SATP or react by losing electrons e) follow periodic trends well or can react by changing electron number they possess f) are typically radioactive or have a high number of protons or have a large atomic mass or do not follow periodic trends well or have a low first ionization energy or have a substantial amount of amount of levels of electrons resulting in a similar large amount of electron-electron repulsion between levels 2. For each of the following observations, identify if the Nuclear model of the atom is able to explain the observation or if the Bohr-Rutherford model (in its pure, original form) is needed? Explain your reasoning in each case. /2 a) all fireworks essentially involve exploding different metals to produce distinct colours the Nuclear model fails to explain this essentially, exploding metals gives them energy which would easily excite electrons, but if the atoms were according to the Nuclear model, a random amount of excitation would occur resulting in random or uniform colours but not distinctly different colours; but the Bohr-Rutherford model with its levels of electrons works because now electrons are moving specific distances resulting in specific colours as defined the number of layers present in that atom /2 b) calcium is less reactive than potassium the Nuclear model can work here calcium has more electrons than potassium resulting in slightly more repulsion, but calcium also has more protons which substantially increases its force of attraction on those electrons which means calcium atoms has a tighter hold on its electrons and thus, it is harder for calcium to let go of any electrons thereby making it less reactive since metals react by losing electrons /1 3.a) Some textbooks refer to effective nuclear charge. What do you think this means? refers to the relative amount of force of attraction acting on the outer level of electrons within an atom (= core charge) /1 b) Explain how it alone affects atomic size. the higher the effective nuclear charge, the smaller the atom because the outer level is pulled closer, but really you need more information to fully or properly explain trends so core charge and nuclear charge are not suitable for explaining trends /1 4. Consider the following atomic sizes (measured in picometers or pm): F = 72, Ar = 87 and Br = 115. Estimate the size of a Cl atom (this is a generous range; if the question was out of 2, you would need to validate a more specific answer somewhere closer to the middle)

3 /4 5. Using the Bohr-Rutherford model of the atom, explain why N is predicted to be the most reactive of C N Ne? Ne is a noble gas so it does not react N has more protons than C so N has a higher force of attraction N has 1 more electron than C, but no difference in levels of electrons so really no significant difference in F R C and N are nonmetals so they react by gaining electrons since N has a higher force of attraction for electrons for the same amount of repulsion compared to C, N is more likely to gain electrons and be more reactive /1 6.a) Using the Bohr-Rutherford model of the atom, predict which element would have the most negative electron affinity: Hf, Ti or Zr? Ti /4 b) Using the Bohr-Rutherford model, fully explain your reasoning. they are all metals so resist gaining electrons which means they all likely have negative electron affinities (so we can't quickly eliminate 1 of them) but they are all in the same column and moving down the column, the number of protons increases so the force of attraction increases substantially moving down the column, the number of electrons and levels of electrons increases so the force of repulsion increases quite substantially due to the increase in levels of electrons, the force of repulsion is increasing faster than the force of attraction which means destabilization through electron addition progressively diminishes (adding 1 more electron to a tremendous amount of repulsion) so that Ti with the least amount of initial repulsion is affected the most 7. For each of the following only use the Bohr-Rutherford model of the atom to: /4 a) predict the atom that would have the lowest fourth ionization energy. Al Si Ga Ge actually, can t really pick the answer until you explain all the factors so do this last since electrons are being removed from the third level for Al Si their ionization energies will be higher to begin with compared to Ga and Ge which are removing electrons from the fourth level so we can eliminate Al and Si now consider what happens when 3 electrons are removed from Ga and Ge so you can see what impact removing the fourth electron will have (I would just do this on the diagram above) now compare the forces holding that fourth outermost electron Ge has 1 more proton than Ga so Ge has a stronger force of attraction but Ge still has one more level electrons than Ga so Ge has a significantly higher force or repulsion therefore, due to the much higher force of repulsion in Ge, it should require less energy to remove that fourth electron compared to Ga

4 /4 b) predict the atom that would be the smallest (+) electron affinity. Be O Se Kr again, can t really pick the answer until you explain all the factors so do this last Be is a metal and Kr is a noble gas so they both have a negative electron affinities so they are eliminated Se has more protons than O so Se has a higher force of attraction Se has more electrons and 1 more level of electrons (sketch the B.R. diagram to check) than O which mean there will be considerably greater force of repulsion in Se so the force of repulsion is increasing faster than the force of attraction for Se so gaining an extra electron will be more challenging in Se; therefore, it will be easier to add one electron to O resulting in a more substantial balancing of forces and thus, more energy is released for O since it will be stabilized to a greater degree (meaning a larger + affinity) thus, Se will have the smallest + electron affinity c) Using the Bohr-Rutherford model, fully explain your reasoning for each of the above. see above /1 8.a) How does the size of a Ni 2+ ion compare to a Ni atom. Ni 2+ is smaller (lost electrons) /3 b) Only use the Bohr-Rutherford model of the atom to explain your reasoning. they both have the same number of protons (same element) and thus, same force of attraction but Ni 2+ has lost 2 electrons but not a level so there is slightly less force of repulsion which means the same force of attraction is more effective at pulling the outer level closer /2 9. An atom has the following successive ionization energies. In which family of the periodic table does this atom belong? Show your work for any marks. I.E. kj/mol I.E I.E I.E I.E I.E I.E. 2 /I.E. 1 = 1145/590 =1.94 I.E. 3 /I.E. 2 = 4912/1145 = 4.29 I.E. 4 /I.E. 3 = 6491/4912 = 1.32 I.E. 5 /I.E. 4 = 8153/6491 = 1.26 it belongs in family 2 since the biggest jump occurs between I.E. 2 and I.E. 3 (some students attempt this question by subtraction, but it is the change in the ratio of energy that matters you must divide) /1 10. Which of the following elements is most likely to gain an electron during a chemical reaction? Mg Si B O O (only B and O are non-metals which react by gaining electrons, but O has a higher force of attraction for about the same force of repulsion)

5 /4 Communication. Answer the following questions on foolscap. /4 11. Draw the Bohr-Rutherford atom for 50 7 Cl. 14 e 8 e 2 e 17 p 33 n 1 mark for number of protons, 1 mark for number of neutrons, 1 mark for total number of electrons and 1 mark for electron distribution -0.5 if you forget to make the nucleus an entire circle it s the only real thing here -0.5 for forgetting the proper short-forms like eg for electron Prepared by K. Zuber