Shapes, And Bond Angles Of Molecules Worksheet printable pdf download

Shapes, And Bond Angles Of Molecules Worksheet

4.2.7 & 4.2.8 Shapes, and bond angles for molecules with two, three and four negative charge centers

The shape of a molecule has an important part to play in determining its chemical (e.g. reactivity and pH) and physical properties (e.g. mpt and

bpt). A negative charge center or region refers to the number of pairs electrons around the central bonded atom. This includes both the lone

(non bonding pairs) pairs and bonded pairs of electrons in single, double or triple bonds. Each double and triple bond counts as one negative

charge center. Watch out for non octet examples.

Shape with respect to the

Number of negative

Bond Angle with respect

number of negative charged

charge centers

to negative charge centers

centers

Linear

180°

Trigonal planar

120°

Tetrahedral

109.5°

Valence shell electron pair repulsion theory (VSEPR)

GN Lewis proposed that chemical bonds resulted when two atoms shared a pair of electrons. The Lewis concept allowed for "electron dot

bookkeeping" in the form of a Lewis dot digram to show how atoms could share electrons to achieve their quota as a noble gas or an octet of

electrons. Lewis originally did not set out to describe the shape of the molecule but it soon became apparent to him that the electron pairs

around the central atom, being like charged, would repel each other. This lead to his VSEPR theory which is still used today to describe the

shape of a molecule.

In VSEPR theory lone pairs of electrons are closer to the central atom and therefore closer to one another than the bonding pairs of electrons

because they are being attracted by the positive protons in the nucleus of one atom instead of two. The lone pairs and bonding pairs of

electrons are arranged around the central atom so as to minimize the repulsion between the lone and bonding pairs of electrons. The relative

magnitude of the electron pair repulsions is:

Lone pair / lone pair > bonded pair / lone pair > bonded pair / bonded pair repulsion

The overall shape according to the VSEPR theory depends on the number of bonding pairs and lone pairs of electrons around the central atom

of a molecule. The overall bond angle is the angle between the bonded atoms attached to the central atom.

Shapes, And Bond Angles Of Molecules Worksheet