{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Ch 10 b - Molecular Geometry Molecules are...

Info icon This preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
Tro's Introductory Chemistry, Chapter 10 1 Molecular Geometry Molecules are three-dimensional objects. We often describe the shape of a molecule with terms that relate to geometric figures. These geometric figures have characteristic “corners” that indicate the positions of the surrounding atoms with the central atom in the center of the figure. The geometric figures also have characteristic angles that we call bond angles .
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
Tro's Introductory Chemistry, Chapter 10 2 Some Geometric Figures Linear Two atoms on opposite sides of central atom. 180° bond angles. Trigonal planar Three atoms form a triangle around the central atom. Planar. 120° bond angles. Tetrahedral Four surrounding atoms form a tetrahedron around the central atom. 109.5° bond angles. 180° 120° 109.5°
Image of page 2
VSEPR Theory Electron groups around the central atom will be most stable when they are as far apart as possible. We call this valence shell electron pair repulsion theory . Since electrons are negatively charged, they should be most stable when they are separated. The resulting geometric arrangement will allow us to predict the shapes and bond angles in the molecule. Tro's Introductory Chemistry, Chapter 10 3
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
Electron Groups The Lewis structure predicts the arrangement of valence electrons around the central atom(s). Each lone pair of electrons constitutes one electron group on a central atom. Each bond constitutes one electron group on a central atom. Regardless of whether it is single, double, or triple. O N O ¥ ¥ ¥ ¥ ¥¥ ¥¥ ¥¥ ¥¥ There are 3 electron groups on N. 1 lone pair. 1 single bond. 1 double bond. Tro's Introductory Chemistry, Chapter 10 4
Image of page 4
Linear Geometry When there are two electron groups around the central atom, they will occupy positions opposite each other around the central atom. This results in the molecule taking a linear geometry . The bond angle is 180°. Cl Be Cl O C O Tro's Introductory Chemistry, Chapter 10 5
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
Trigonal Geometry When there are three electron groups around the central atom, they will occupy positions in the shape of a triangle around the central atom. This results in the molecule taking a trigonal planar geometry . The bond angle is 120°. F F B F Tro's Introductory Chemistry, Chapter 10 6
Image of page 6
Tetrahedral Geometry When there are four electron groups around the central atom, they will occupy positions in the shape of a tetrahedron around the central atom. This results in the molecule taking a tetrahedral geometry . The bond angle is 109.5°. F F C F F Tro's Introductory Chemistry, Chapter 10 7
Image of page 7

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

View Full Document Right Arrow Icon
Sketching a Molecule Because molecules are three-dimensional objects, our drawings should indicate their three-dimensional quality By convention:
Image of page 8
Image of page 9
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