Unit 10: Covalent Compounds Flashcards
When do covalent bonds form?
When atoms SHARE ELECTRONS to complete octets.
Covalent bonds form between…
two non-metals (groups 4A-7A)
What are used in the names of covalent compounds?
prefixes
prefix for 1
mono
mono
prefix for 1
prefix for 2
di
di
prefix for 2
prefix for 3
tri
tri
prefix for 3
prefix for 4
tetra
tetra
prefix for 4
prefix for 5
penta
penta
prefix for 5
prefix for 6
hexa
hexa
prefix for 6
prefix for 7
hepta
hepta
prefix for 7
prefix for 8
octa
octa
prefix for 8
prefix for 9
nona
nona
prefix for 9
prefix for 10
deca
deca
prefix for 10
How to name covalent compounds:
STEP 1 Name the first nonmetal by its element name.
STEP 2 Name the second nonmetal with an ide ending.
STEP 3 Add PREFIXES to indicate the number (from subscripts) of atoms of each nonmetal.
In a hydrogen molecule (H2), each H atom… (3)
- shares electrons to form a SINGLE COVALENT BOND
- acquires TWO electrons.
- becomes STABLE like helium (He).
What does a covalent bond indicate?
the atoms share electrons
In a fluorine F2 molecule, each F atom…(2)
- shares ONE electron.
- acquires an OCTET (8 electrons)
Which orbital does the bonding pair come from? (for molecules that form octets?
P orbital
If carbon has 4 valence electrons, how many bonds can it form?
four
The number of covalent bonds can be determined from…
the number of electrons needed to complete an octet
Steps to writing electron-dot formulas
STEP 1 Determine the arrangement of atoms.
STEP 2 Determine the total number of valence electrons.
STEP 3 Attach each bonded atom to the central atom with a pair of electrons.
STEP 4 Place remaining electrons as lone pairs to complete octets (2 for H atoms).
STEP 5 If octets are not complete, form a multiple bond by converting a lone pair to a bonding pair.
How many electrons are shared in a single bond?
One Pair
How many electrons are shared in a double bond?
Two Pairs
How many electrons are shared in a triple bond?
Three Pairs
What bond does a nitrogen molecule have?
triple
How to count lone pairs?
The pairs attached to the central atom that are not in a bond
Exceptions to the octet rule
group 3 elements, elements on the 3rd row, and beryllium and chloride
Why are there exceptions for group 3 elements?
they only have 3 valence electrons to bond with
Why are there exceptions to elements on the 3rd row?
Elements on the 3rd row have the d-orbital available to place surplus electrons
Why are there exceptions to beryllium and chloride?
has a small atomic radius, which makes it small enough
Polar molecules
molecules that contain polar bonds
Nonpolar molecules
molecules that contain no polar bonds or have a symmetrical arrangement of polar bonds
Polar bonds
Covalent Bonds with an unequal share of electrons because onr end has a higher electron density
Nonpolar bonds
Covalent bonds with an equal share of electrons
Though atoms often form compounds by sharing electrons, the electrons are not always _________
SHARED EQUALLY
When two atoms share electrons unequally, a ______ results.
Dipole
The greater the difference in electronegativity, the __________ the bond is.
More Polar
Electronegativity difference for nonpolar
0-0.4
Electronegativity difference for polar
0.5-1.9
Electronegativity difference for ionic
2.0-4.0
Are polar molecules symmetrical or asymmetrical?
asymmetrical
Are nonpolar molecules symmetrical or asymmetrical?
symmetrical
Polar molecules must contain…
polar bonds
How can polar bonds be determined?
through differences in electronegativity of atoms
Symmetrical Molecules have…
polar bonds that cancel each other out
Examples of symmetrical molecules
Linear (more than 2 atoms), Tetrahedral, Trigonal Planar
Examples of Asymmetrical molecules
Bent and Linear w/ 2 Atoms
What forces form between ionic compounds?
electrostatic interactions
What forces form between covalent compounds?
dipole-dipole, hydrogen bonds, (London) dispersion forces
Electrostatic interactions are the ______ forces
strongest
Dispersion forces are the ________ forces
weakest
Dipole-dipole attractions
interaction between +ve end of one molecule and a -ve end of another
Hydrogen Bond forms when
Hydrogen atoms in one molecule are attracted to the atoms F, O, or N in another molecule.
Dispersion forces are…
Weak attractions between nonpolar molecules and caused by the MOVEMENT OF ELECTRONS
Dipole Moment
a measure of the separation of positive and negative charges within a system, or its overall polarity
(magnitude 1 x distance between atoms)
