Periodic Trends - To students: To help clarify the periodic...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
To students: To help clarify the periodic trends we've discussed in class, I've written the following review – please read it and confirm for yourself that you understand the material. It will help you on the quizzes and exams to come. Please see me if you need additional help. Atomic Size : As you go down a group, the outer/valence electrons reside in energy levels (n shells) that are farther and farther from the nucleus (increasing n levels). Also, these outer/valence electrons are partially "shielded" by the inner (lower n levels) electrons from the electrostatic attraction from the protons in the nucleus. These two things – the higher n levels and the effect of electronic shielding – cause a trend in increasing atomic size down a group. As you go across a period, the n value remains the same across the period, so the added outer/valence electrons are all residing in the same energy level, and therefore the shielding by inner (lower n levels) electrons remains the same across the period. But as you go across the period, the number of protons in each atom's nucleus is increased, and therefore the effective nuclear charge (Z eff ) increases. The result is that as you go across the period, the valence electrons are being pulled closer and closer to the nucleus, and therefore the atomic size decreases as you go across the period. Ionization Energy : In the case of "ionization energy", the "ionization" refers to the removal of an electron from an atom or ion (or more precisely, the removal of one mole of electrons from a mole of gaseous atoms or ions): Atom(g) Cation(g) + + e - ΔE is (+) due to separation of charged particles Removal of a charged particle from an oppositely-charged particle is always an
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 3

Periodic Trends - To students: To help clarify the periodic...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online