Chapter 4: Covalent Compounds

bent angle

104.5-105 degrees two bonds, two lone pairs EX: H2O

trigonal pyramidal

107 degrees 3 bonds, 1 lone pair Ex. NH3

Tetrahedral

109.5 degrees surrounded by four groups EX: CH4

trigonal planar

120 degrees surrounded by three groups EX: H2CO

linear bond

180 degrees surrounded by two groups EX: CO2

triple bond

A chemical bond formed when atoms share three pairs of electrons

double bond

A chemical bond formed when atoms share two pairs of electrons

two-electron bond

A covalent bond is a ______________ ___________ in which the bonding atoms share valence electrons.

diatomic molecule

A molecule consisting of two atoms

nonpolar

A molecule with no polar bonds is a ______________ molecule.

polar

A molecule with one polar bond is a _______________ molecule.

compound

A substance made up of atoms of two or more different elements joined by chemical bonds

octet

Atoms with four or more valence electrons form enough bonds to give an ____________.

respectively

Atoms with one, two, or three valence electrons form bonds ___________________.

nonmetals

Covalent bonds are formed between _____________________ and/or metalloids.

➢H, accommodates only 2 e− in bonding. ➢ Elements in group 3A do not have enough valence e− to form an octet in a neutral molecule. ➢ Elements in the third row have empty d orbitals available to accept electrons. Thus, elements such as P and S may have more than 8 e− around them.

Exceptions to the octet rule: (there are 3)

8-(number of valence electrons)

How do you predict the number of bonds for an atom with more than four valence electrons?

nonpolar

If the electronegativities of two bonded atoms are equal or similar (the difference is less than 0.5), the bond is _______________.

polar

If the electronegativities of two bonded atoms are larger than 0.5 but less than 1.9, the bond is a ________________ covalent bond.

noble gas

In covalent bonding, elements try to acquire the electron configuration of the nearest __________ ___________.

No polar bonds Individual bond dipoles that cancel

Nonpolar molecules generally have what two things?

One or more polar bonds Individual bond dipoles that do not cancel

Polar molecules generally have what two things?

The polarity of the individual bonds The overall shape of the molecule

The classification of a molecule as polar or nonpolar depends on what two things?

nonpolar

The electrons in the bond are being shared equally between the two atoms.

polar

The electrons in the bond are unequally shared.

electronegative

The higher the value, the more _______________________ an atom is and the more it is attracted to the electrons in a bond

N2, O2, F2, Cl2, Br2, I2, H2

What are the seven diatomic molecules?

➢ determine how many groups surround the atom. ➢ Ignore multiple bonds in predicting geometry. Count only atoms and lone pairs. ➢ The most stable arrangement keeps the groups as far away from each other as possible.

What are the three steps in determining molecular shape of covalent compounds?

Identify all polar bonds based on electronegativity differences Determine the shape around individual atoms by counting groups Decide if individual dipoles cancel or reinforce.

What are the three steps in determining the polarity of a molecule with two or more polar bonds?

Number of bonds + Number of lone pairs = 4

What is the general rule for bonding elements (except for hydrogen, H)?

Add

____________ one valence electron for each negative charge.

Subtract

_____________ one valence electron for each positive charge.

covalent compound

a chemical compound formed by the sharing of electrons

molecule

a compound or element containing two or more atoms joined together with covalent bonds

Electronegativity

a measure of an atom's attraction for electrons in a bond.

Valence Shell Electron Pair Repulsion (VSEPR) Theory

a molecular model to predict the geometry of the atoms making up a molecule where the electrostatic forces between a molecule's valence electrons are minimized around a central atom.

dipole

a partial separation of charges.

Lewis Structures

electron-dot structures for molecules. They show the location of all valence electrons.

molecular formula

shows the number and identity of all of the atoms in a covalent compound, but not which atoms are bonded to each other.

-ide

suffix for naming covalent molecules

non-bonded electron pairs (lone pairs)

the unshared valence electron pairs in a covalent bond

Resonance

two Lewis structures having the same arrangement of atoms but a different arrangement of electrons.