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a neutral group of atoms joined together by covalent bonds
- atoms held together by sharing of electrons
- -tug of war between aroms over the elecrtons
- B2, I2, N2, Cl2, H2, O2, F2
- -a molecule of consisting of 2 atoms
- compound made of molecular (covalent) bonds
- -low melting and boiling points
- -gases or liquids at room temp.
- -made of 2 or more non-metals**
- the chemical formula of a molecular compound
- -show actual quantity of each element a molecule contains
- -not always in lowest terms
octet rule in covalent bonding
- electrons sharing in covalent bonding allows for noble gas configuration
- -various element groups 4A,5A,6A,7A of ten form covalent bonds
single covalent bonds
two atoms held together by sharing 1 pair of electrons
shows shared electrons by a single dash
other valence electrons not shared, also called lone pair or nonbonding pair
double and triple covalent bonds
bonding by sharing more than 1 pair of electrons
double covalent bond
bond formed by sharing of 2 pairs of electrons
triple covalent bond
bond formed by sharing of three pairs of electrons
coordinate covalent bonds
a covalent bond in which one atom contributes both bonding electrons
a tightly bound group of atoms that has a positive or negative charge and behaves as a unit
how to draw lewis structure
- 1. determine position
- 2. find the total number of electrons available for bonding
- 3. place a single covalent bond between all pairs of atoms
bond dissociation energy
- the energy required to break a bond between to covalently bonded atoms
- -expressed as the energy needed to break 1 mole of bonds
large dissociation energy means..
a very strong bond
two or more valid electron dot structures that have the same number of electron pairs for a molecule or ion
exceptions to the octet rule
- -cant work in molecules whose total number of valence electrons is an odd #
- - some molecules have fewer than or more than a complete octet
binary molecular compounds (naming them)
- prefixes are used to indicate the number of atoms of each type that are present in a compound
- 1-mono 2-di 3-tri 4-tetra 5-penta 6-hexa 7-hepta 8-octa 9-nona 10-deca
- overlapping atomic orbitals of different elements that apply to the whole new molecule
- -each molecular orbital will hold up to 2 electrons
molecular bonding results from..?
an imbalance between attractions and repulsions of nuclei and electrons of bonded atoms
the orbital holding electrons of a covalent bond
- molecular orbital formed when two atomic orbitals combine to form a summetrical orbital around the 2 nuclei
- -p atomic orbitals can also overlap end to end and form sigma bonds
- bonding electrons found in irregular ovals above and below the nuclei of the bonding atoms
- -weaker than sigma bonds
- -atomic orbitals overlap less so less attraction
how do p atomic orbitals make pi bonding orbitals?
from side by side overlapping p orbitals
- valence shell electron pair repulsion
- -gives shape and bond angles to molecules so that valence electrons pair stay as far apart as possible.
all bond angles are 109.5 degrees
bond angles are 107 degrees
several atomic orbitals mix to form the same total number of equivalent hybrid orbitals; gives info. about bonding and shape.
nonpolar covalent bond
bonding electrons equally shared
polar covalent bond
- bonding electrons are not shared equally
- -also called polar bond
- -one of the atoms pulls harder
- -the electrons are more likely to be found orbiting the one that pulls harder
- relative ability to attract an electron while it is bonded
- -ranked on a scale of 0-0.4
- -in polar bond the more electronegative atom attracts electrons more strongly, gains slight negative charge
- -less electronegative atom has a slight positive charge.
a molecule having one end slightly negative and one end slightly positive
a molecule with two poles of charge; also called dipolar; orient themselves in an electric field
polarity of a molecule is affected by....
bond polarity and shape
intermolecular forces are weaker than...
ionic or covalent bonds
van der waals forces
weakest attractions between molecules; named for dutch chemist Johannes van der waals
dipole interactions (2 kinds)
- dipole-dipole: occur when polar molecules are attracted to one another; electrical attraction between oppositely charged regions of polar molecules; similar to but much weaker than ionic bonds
- dispersion forces:caused by the motion of electrons creating a temporary dipole as they orbit an atom; weakest of all molecular interactions
- a hydrogen covalently bonded to a very electronegative atom is also weakly bonded to an unshared pair of electrongs in another electronegative atom
- -bonding occurs with N,O, and F
- solids held together by intermolecular forces such as dipole-dipole, dispersion, hydrogen bonding, etc.
- EX. fats, waxes
- -properties: soft, low MP
covalent network solids
- solids held together by extended network of covalent bonds
- EX. diamond, quartz
- -properties: hard, high MP
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