Chem 9

What is a covalent bond

Chemical bond that results in the sharing of valence electrons

a covalent bond forms between two ___

nonmetals

How does a covalent bond form?

2 nonmetals- attractive and repulsive force- attractive force is greater- they bond and share electrons

List the elements that exist as diatomic molecules. Why do they exist as diatomic molecules?

Hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, iodine

What is a single covalent bond?

one pair of electrons is shared

What two things does the strength of a covalent bond depend on?

bond length and bond dissociation energy

What is bond length?

distance between two bonding nuclei

How are bond length and shared pairs of electrons related?

as the number of shared pairs increases the bond length decreases

How are bond length and strength of the bond related?

shorter the bond length the stronger the bond. single < double < triple

What is bond dissociation energy?

amount of energy needed to break a covalent bond.

How are bond length and dissociation energy related?

2 atoms bonded closer more energy needed to separate

What are resonance structures?

condition that occurs when more than one valid lewis structure can be written for a molecule

What does VSEPR stand for?

Valence Shell Electron Pair Repulsion Model

What is the VSEPR theory?

minimizes the repulsion of shared and unshared pairs of electrons around the central atom

What is a bond angle?

the angle formed by any two terminal atoms and a central atom

Draw the linear shape and describe.

2 shared pairs, 0 lone pairs, nonpolar

Draw a bent shape and describe.

2 shared pairs, 2 lone pairs, polar

Draw a tetrahedral shape and describe.

4 shared pairs, 0 lone pairs, nonpolar

Draw a trigonal planar shape and describe

3 shared pairs, 0 lone pairs, polar

Draw a trigonal pyramidal shape and describe.

3 shared pairs, 1 lone pair, polar

When are two atoms likely to form a double bond?

...

When are two atoms likely to form a triple bond?

...

What is electronegativity?

Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons.

What is a nonpolar covalent bond?

equal sharing of electrons. 2 nonmetals same electronegativity

What is a polar covalent bond?

unequal sharing of electrons, difference in electronegativity

Where do the electrons spend more time in a polar covalent bond?

around one atom. the atom is momentarliy negative. the other atom is momentarily positive, creates a dipole- 2 poles

What did the paddles represent in the molecule building kits?

lone pairs of electrons

Where are lone pairs located?

the central atom

How many electrons do two atoms in a double covalent bond share?

4

a structural formula shows the arrangement of the atoms in a molecule

true

in molecules, hydrogen is always a terminal atom

true

the number of bonding pairs in a molecule is equal to the number of electrons

false

to find the total number of electrons available for bonding in a positive ion, yo should add the ion charge to the total number of valence electrons of the atoms present

false

resonance occurs when more than one valid lewis structure can be written for a molecule

true

nitrate is an example of an ion that forms resonance structures

true

the carbon dioxide molecule contains two double bonds

true

all electrons in an atom are available for bonding

true

when carbon and oxygen bond, the molecule contains ten pairs of bonding elements

false

the vespr model is used mainly to

determine molecular shape

the bond angle is the angle between

two terminal atoms and the central atom

the vespr model is based on the idea that

shared and unshared electron pairs repel each other as much as possible

the shape of a molecule whose central atom has four pairs of bonding electrons is

tetrahedral

the shape of a molecule that has two covalent single bonds and no lone pairs on the central atom is

linear

the shape of a molecule that has three single covalent bonds and one lone pair on the central atom

triagonal pyramidal