Today my students created their own explanations for the trends and discontinuities in first ionisation energies across a period and down a group.
Using only the assumptions provided and the IB Chemistry data booklet each pair of students was assigned a trend to explain to the class. Students were encouraged to use Bohr diagrams and electrons configurations to support their explanations.
- If enough energy is absorbed by an electron it can leave the electron altogether n = 1 to n = infinity
- The first ionization energy is the energy required to completely remove the first electron from an atom in its gaseous state. E.g K(g) → K+(g) + e– I.E = 419 kJmol-1
- Valence electrons are the electrons found in the outer subshell of an atom. They are also called outer shell electrons.
- During the first ionization the electrons are removed from the outermost or valence shell.
- As the amount of energy needed to remove a valence electron increases the ionization energy increases.
- An energetically stable atom will have subshells that are full or half full.
- The attraction between the protons in the nucleus of an atom and the valence electrons increases when the number of protons increases.
- The attraction between the positive protons and negative valence shell electrons decreases as the distance between them increases.
- The inner energy levels shield the valence shell electrons from the protons in the nucleus decreasing the force of attraction between them.
- Explain why the first ionization energies for the group 18 elements decrease down the group.
- Explain why the first ionization energies for the group 1 elements decrease down the group.
- Explain why the first ionization energies for the group 18 elements (He, Ne and Ar) are higher that the group 1 elements groups.
- Explain why the first ionization energies of the elements of the third period (Na, Mg, Al, Si, P, Cl, Ar) have a general increasing trend.
- Explain why the ionization energy of Al is lower than Mg.
- Explain why S has a lower than expected first ionization energy than P.
|Chemistry syllabus & cross curricular links||12.1|
|Prior knowledge||2.2. Evidence for the existence of electrons on energy levels provided by the emission spectrum of hydrogen was used as the basis of this new learning|
|Learner Profile||Thinkers, Communicators|
|Approach to Teaching||Inquiry based.|
|Approach to Learning||Thinking skills|
|Nature of Science (NOS)||Experimental evidence supports theories about the existence of electrons in energy levels (1.8)|