{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

ch.7 - What!are!the!Goals(Chapter!7...

Info icon This preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
10/14/2009 1 What are the Goals (Chapter 7)? Learn how the periodic table can help us understand the properties and chemistry of the elements. Understand the concept and implications of effective nuclear charge. Learn about periodic trends of the sizes of atoms and their ions. Learn about ionization energies and their periodic trends trends. Learn about electron affinities and their periodic trends. Begin to learn about descriptive chemistry of the elements and related periodic trends. Screening (Shielding) Effective Nuclear Charge “inner electrons shield outer electrons” an outer electron (in an orbital further from the nucleus) i inner electrons e- experiences an effective nuclear charge of Z * << Z Z Screening (Shielding) of electrons: s < p < d < f We say that, within a shell (the same value of n for all electrons), s electrons are screened less than p electrons, p electrons are screened less than d electrons, etc…
Image of page 1

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

View Full Document Right Arrow Icon
10/14/2009 2 Notes: - core electrons screen valence electrons - electrons within a subshell do not screen each other very well (a 2 p electron does not screen other 2 p electrons 11 Na 1 s 2 s 2 p 3 s 2 2 6 1 valence electron 10 ! core electrons 11+ ! Combined effect = 11 ! 10 = +1 The valence electron in a Na atom “experiences” attraction of the effective nuclear charge of at least +1. Penetration The probability of finding electrons belonging to a given orbital close to the nucleus, at least some of the time , decreases with l We say that s electrons penetrate better to the nucleus compared to p electrons Penetration by electrons: s > p > d > f 3 s
Image of page 2
10/14/2009 3 Z * attraction between electrons and nucleus E electron screening penetration & In summary for many-electron atoms : within a shell (same n ), l E 3 s 3 p 3 d 4 s 4 p 4 d 4 f Recall from Ch. 6: l = 0, 1, 2, 3, … s p d f 1 s 2 s 2 p ases Atomic Radius (atomic size) , R A creases, size increa R A (Na) R A (Al) R A (Na) R A (Rb) < > Z * decreases, size increases n inc R A (S) R A (Cs) R A (I) R A (F) R A (O) R A (N) R A (F) R A (Sb) < < < >
Image of page 3

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

View Full Document Right Arrow Icon
10/14/2009 4 Atomic Size The size of an atom increases as n increases ( going down a column of the going down a column of the periodic table ). This point was made as we introduced the Bohr model of the atom and then the quantum mechanical model of the atom (Chapter 6) Atomic radii decrease from left to right in a row - Why? the inability of electrons in the outer shell (highest n ) to fully shield other electrons in the same shell from the charge of the nucleus (which of course increases as you move left to right). e- with lower n shield the outer electrons quite well. e- with same n and lower l shield the outer shield the outer electrons partially. e- in the same outer subshell shield each other rather poorly.
Image of page 4
10/14/2009 5 Fig. 7.7 Example Arrange Se, P, As, S in order of increasing atomic radius.
Image of page 5

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

View Full Document Right Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern