Last modified: Sun 01/17/2016 07:00:10 pm BCE

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Answer all of the questions below. If you do not know an answer enter CNA. However, it will help me the most if you answer each question with your best intuition/idea about what would be a reasonable answer.


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According to Coulombs Law the potential energy (E) between two stationary charged particles is approximated by the equation shown above, where q1 and q2 are the charges on the particles (for example -1 charge for an electron and a +1 charge for the nucleus), d is the separation between the charged particles in picometers (1 pm = 10-12 m).

The first ionization energy is defined as, 'the amount of energy required to remove an electron from a neutral atom.' The equation that was written to describe this process for a general atom A in the gas phase is,

A(g) = A+(g) + 1e-

For the element hydrogen the equation describing the ionization energy would be,

H(g) = H+(g) + 1e-

The 1st ionization energy for hydrogen is 1312 kJ mol-1. This can be represented in the following figure.

In the figure above the energy level diagram for a hydrogen atom is shown on the left. The one electron in hydrogen is shown in the n = 1 level. To remove the electron (shown on the right side of the figure, 1312 kJ/mol of energy is required to remove the electron from the hydrogen atom.

 

1. The 1st ionization energy for helium is 2372 kJ mol-1.

He(g) --> He+(g) + 1e-

Which of the following is the best explanation for why the 1st ionization energy for helium is nearly twice the 1st ionization energy for hydrogen. (Pick one)

a) helium has a greater mass than hydrogen;

b) helium is more stable (a noble gas), so it takes more energy;

c) the electrons in helium are closer to the nucleus compared to the electron in hydrogen;

d) the electrons in helium is twice as far away as the electron in hydrogen;

e) helium has twice as many protons as hydrogen, and the electrons in helium are about the same distance from the nucleus as the electron in hydrogen;

f) helium has twice as many electrons as hydrogen so it takes twice as much energy to remove an electron from helium compared to an electron in hydrogen;

g) helium has twice as many protons as hydrogen.

 

2. According to Coulombs Law what happens to the magnitude of the ionization energy as the nuclear charge (number of protons) increases? (Pick one)

a) the number of electrons increase, so the ionization energy increases;

b) the number of electrons increase, so the ionization energy decreases;

c) the electrons experience a greater attraction to the nucleus, so the ionization energy increases;

d) the electrons experience a smaller attraction to the nucleus, so the ionization energy decreases

e) the electrons get further from the nucleus;

 

3. According to Coulombs Law what happens to the magnitude of the ionization energy as the electrons get further from the nucleus? (Pick one)

a) there is more space for the electrons, so the ionization energy decreases;

b) electron-electron repulsions increase, so the ionization energy increases;

c) the electrons experience a greater attraction to the nucleus, so the ionization energy increases;

d) the electrons experience a smaller attraction to the nucleus, so the ionization energy decreases

e) the electrons experience a smaller attraction to the nucleus, so the ionization energy increases;

 

4. Consider the element lithium, if we assume that the three electrons in lithium are the same distance from the nucleus as the electrons in hydrogen and helium estimate the 1st ionization energy for lithium? (Pick one)

a) about 2400 kJ mol-1;

b) about 1300 kJ mol-1;

c) about 3400 kJ mol-1;

d) about 5200 kJ mol-1;

 

5. The first ionization energy for lithium is actually known to be 520 kJ mol-1. Comparing this 1st IE to the 1st IE's for hydrogen and helium, how would you explain lithium's 1st IE based upon the ideas presented in Q2 and Q3 above. (Pick one)

a) the electron that is removed must be further from the nucleus, reducing the 1st ionization energy;

b) lithium has more electrons that repel each other, reducing the 1st ionization energy;

c) the electron to be removed needs more space, so the 1st ionization energy will be smaller;

d) the mass of the lithium nucleus is greater, reducing the 1st ionization energy;

e) lithium is in a different row in the periodic table;

 

6. The first ionization energy for beryllium is known to be 899 kJ mol-1. The electron that is removed from beryllium must be; (Pick one)

a) the same distance away from the nucleus as an electron removed from the lithium atom;

b) the same distance away from the nucleus as an electron removed from a hydrogen atom or a helium atom

c) a greater distance from the nucleus compared to an electron removed from the lithium atom;

 

7. The 1st ionization energies as we continue across the periodic table from boron (800 kJ mol-1) to neon (2081 kJ mol-1) continue to (in general) increase. What factor(s) best explain this general increase as we proceed from boron to neon? (Pick all that apply.)

a) the nuclear charge increases;

b) the electrons are at the approximately same distance;

c) the mass of the nucleus increases;

d) the electrons require more space;

e) the electrons are getting further from the nucleus;

 

8. The atom following neon in the periodic table is sodium. Its 1st ionization energy is 495 kJ mol-1. How would you explain this ionization energy? (Pick one)

a) sodium is in a different row in the periodic table;

b) sodium has more electrons that repel each other, reducing the 1st ionization energy;

c) the electron to be removed needs more space, so the 1st ionization energy will be smaller;

d) the mass of the sodium nucleus is greater, reducing the 1st ionization energy;

e) the electron that is removed must be further from the nucleus, reducing the 1st ionization energy;

 

9. Would you predict there to be a steady increase, decrease or no change in the 1st IE's for elements as we move from Na to Ar? (Pick one)

a) increase;

b) decrease;

c) no change;

10. Is there anything about the questions that you feel you do not understand? List your concerns/questions.

11. If there is one question you would like to have answered in lecture, what would that question be?