Covalent Compounds

What determines whether two atoms will form a bond?

How can a hydrogen atom, which has one valence electron, bond w/ a chlorine atom, which has seven valence electrons?

What happens in terms of energy after a hydrogen atom bonds w/ a chlorine atom?

Pre-chapter questions

Covalent bond: sharing of a pair of electrons. The electrons move in the space surrounding

the nuclei of the two atoms (molecular orbital).EX: H2, O2, N2 (diatomic molecules)

Shared electrons gives stability to both atoms.NOT all compounds are either ionic or

covalent.

Covalent bonds

Most atoms become more stable in compound.

Energy is released during bond formation. Potential energy goes down as atoms get closer

and the system gives off energy. PE determines bond length, minimum potential

energy.

Energy & Stability

Bonded atoms vibrate, and vary in strength. Covalent bond is flexible.

Distance varies and vibrations occur (what is this similar to?)

Bond energy – energy needed to break a bond between two atoms. Shorter bonds tend to be stronger (high bond

energy)Strong bonds tend to have H and F in it.

Energy & Stability

Non-polar covalent bond – bonding electrons in the molecular orbital are shared equally. Ex: H2, values equal

Polar covalent bond – electron shared unequally.Ex: C and O, values unequal

May turn into ionic bond

Electronegativity & Covalent Bonding

Have positive and negative ends. Dipole - molecule that has one end partially

neg. and the other partially pos.Ex: HF (delta symbol)

Polar bonds

Related to bond strength. The greater the electronegativity values of

two elements, the greater the polarity. The greater the polarity the more energy needed to break it and therefore it is strong.

Polarity

I will divide you into groups and assign your group an element from group 13. I will also assign your group another periodic group number and with the element I assigned from group 13, you will decide what type of bond it will form with all the other elements in the second group I assigned you. USE ELECTRONEGATIVITY!!!!

Activity

Electronegativity & Bond Types