covalent bonding
what are the exceptions to the octet rule?
1) hydrogen only has 2 atoms 2) beryllium has a max of 4 valence electrons 3) boron compounds are stable with only 6 valence electrons
what is electron affinity?
ability of an atom to attract and hold additional charges
atoms actually move back and forth but maintain an ____ _____ _____
average distance apart
uneven sharing results when there is a great difference in ____________
electronegativity
to predict if a molecule will be polar or nonpolar, study the _____________ __________
electronegativity values
covalent bonds form because _______________________
electrons of one atom are attracted to the positive nucleus of another atom
the more electrons, the more likely _____
electrons will pile up on one side and cause a temporary positive end and temporary negative end on a bond
if 2 atoms begin to move apart, attractive forces between the _____ of one atom and the ______ of the other atom pull them back together
electrons; nucleus
any time a chemical bond forms, _____ is released
energy
what is an exothermic reaction?
energy is released as atoms move from a high energy state to a low energy state when covalent bonds form
nonmetals seek to _____ electrons to make them stable
gain
if a bond has few electrons, it's likely to be a ______
gas
all nonmetals have _____ electronegativity and ______ electron affinity
high
mono
1
what are the guidelines for covalent bonding of unlike atoms?
1) add up valence electrons of each atom 2) divide the total number of electrons by 2 to get total number of electron pairs available 3) element with lowest electronegativity is the central atom 4) hydrogen is always a terminal atom - it can only connect to one other atom because it can only form one bond 5) place one pair of electrons (represented by a dash) between each pair of bonded atoms 6) subtract number of pairs used from number of pairs available 7) place lone pairs around each terminal atom to satisfy octet rule 8) convert one or more terminal atom lone pairs into double or triple bonds - only for CNOPS
what are some intermolecular attraction characteristics?
1) attractions between molecules 2) weaker than ionic or covalent bonds 3) determines if a molecular compound is a solid, liquid, or gas 4) best indicator of strength of intermolecular forces: boiling point
what are characteristics of multiple bonds?
1) commonly formed by carbon, nitrogen, oxygen, phosphorus, sulfur 2) stronger than single bonds 3) increase the electron density between to nuclei. as the electron density increases, the repulsion between the two nuclei decreases. also as the electron density increases, the attraction each nucleus has for the additional bonding electron pairs increases. both of these effects draw the nuclei closer together, shortening the bond length
what are characteristics of ionic bonds?
1) electrons are transferred between atoms having large differences in electronegativity 2) contain a metal and nonmetal 3) strong electrostatic attractions between positive and negative ions 4) formulas given in simplest ratio of elements 5) crystalline structures that are solid at room temperature 6) form crystal lattice 7) high melting/boiling point 8) good conductors of electricity when melted or dissolved
what are the steps in naming molecular compounds?
1) list 1st name of element in compound. if more than one atom is present, include a prefix to indicate that number of atoms 2) list 2nd name of element in compound. always include a prefix indicating number of atoms of 2nd element and use "ide" suffix
what are the three types of intermolecular forces?
1) london forces 2) dipole dipole 3) hydrogen bonding
what are some properties of molecular compounds?
1) low melting and boiling points 2) poor electrolytes - does not conduct electricity well
what are some characteristics of covalent bonds?
1) share electrons between atoms having small differences in electronegativity 2) 2 nonmetals 3) formulas that are given in the true ratio of atoms 4) exist in any state of matter at room temperature 5) low melting/boiling points 6) nonconductors of electricity
what are some characteristics of dipole dipole intermolecular forces?
1) strong intermolecular force 2) forms between polar molecules 3) caused when the positive end of one molecule is attracted to the negative end of adjacent molecules 4) similar to electrostatic forces between ions, but much weaker
what are some characteristics of hydrogen bonding?
1) strongest type of intermolecular force 2) lone pair of electrons has a strong negative charge; the positive end of one polar molecule is attracted to a lone pair of electrons from another molecule 3) usually occurs when H is covalently bonded to F, Cl, N, or O
what are some characteristics of london forces?
1) weakest intermolecular force 2) forms between nonpolar molecules 3) caused by motion of electrons 4) electrons of one atom attracted to positive nucleus of adjacent atoms 5) the more atoms present, the greater the attraction
how many valence electrons do metals have?
1-3
deca
10
v shape, bent, or angular
104.5 degrees
trigonal pyramidal
107 degrees
tetrahedral
109.5 degrees
trigonal planar
120 degrees
linear
180 degrees
di
2
what is covalent bonding an analogy of?
2 equally strong people playing tug-of-war - neither can pull the rope harder than the other one
a covalent compound is a bond between _____ ____________
2 nonmetals
tri
3
tetra
4
penta
5
how many valence electrons do nonmetals have?
5-7
hexa
6
hepta
7
octa
8
nona
9
what are the 7 diatomic molecules?
H2, N2, O2, F2, Cl2, B2, I2
what does a polar covalent bond result in?
a dipole
what does a covalent bond form?
a molecule
what is a dipole?
a molecule with oppositely-charged ends; oxygen pulls the negative pair of electrons closer to it; pulls electrons slightly away from hydrogen atom so molecule has a negative end and a positive end
what is a molecule?
a neutral group of atoms that are held together by covalent bonds
a dash between 2 elements that are covalently bonded and written in lewis dot notation represents
a single covalent bond
inter means
between
_______ a bond requires energy
breaking
what are intramolecular forces of attraction?
chemical bonds which are the attractive forces between atoms with a compound
what is the valence shell electron pair repulsion theory?
electron pairs repel one another so molecules adjust their shapes so that electron pairs are as far apart as possible
___________ values are used to predict the type of bond that will form between the atoms of 2 elements
electronegativity
if electronegativity difference is greater than or equal to 2.0
ionic bond
if the central atom is from PERIODS 3-7, what happens?
it can accommodate more than 4 electron pairs, due to the presence of d orbitals
all diatomic molecules have a _________ shape
linear
if a bond has an average amount of electrons, it's likely a ________
liquid
what state are most molecular compounds at room temperature?
liquids or gases
large atoms have more energy levels of electrons, so there are _____ bond lengths, therefore _____ energy is required to separate atoms
longer; less
covalent compounds are also called ______ compounds
molecular
a double or triple bond requires _____ energy to break than a single bond
more
the higher the boiling point, the _______ _________ the particles are attracted to each other
more strongly
if 2 electrons are shared equally, a _________ is formed
nonpolar covalent bond
if electronegativity difference is less than 0.4
nonpolar covalent bond
a single bond represents _____ pair of electrons shared
one (2 electrons)
in a covalent bond, shared electrons fill the _____ orbitals of both atoms, making them both stable
outer
if electronegativity difference is from 0.5 to 1.9
polar covalent bond
when one atom has a stronger attraction for a pair of electrons than another, a _________ is formed
polar covalent bond
if 2 atoms move too close, the 2 _______ __________ repel each other, and the atoms move apart
positive nuclei
if 2 atoms of the same nonmetal element react with each other, electrons will be _________ _________ between them; neither atom has a greater attraction for the shared electrons
shared equally
when bond lengths are ______, atoms are very close, and ____ energy is required to separate them
short; more
if a bond has a lot of electrons, it's likely a ______
solid
when unlike atoms share electrons, one atom may have a _________ ___________ for the shared pair of electrons
stronger attraction
what is electronegativity?
tendency of an atom to attract a shared pair of electrons
what is bond length?
the average distance (space) between two nuclei that are bonded together
what is bond dissociation energy?
the energy required to break a bond between two covalently bonded atoms
what are intermolecular forces of attraction?
those occurring between molecules and are responsible for properties such as boiling point, freezing point, and physical state
a triple bond represents ______ pairs of electrons shared
three (6 electrons)
a double bond represents _____ pairs of electrons shared
two (4 electrons)
only ________ are involved in bonding
valence electrons
intra means
within