chemical bond
mutual electrical attraction between the nuclei and valence electrons of different atoms that bind the atoms together
lewis structure
formula in which atomic symbols represent nuclei and inner-shell electrons,
dot-pairs or dashes between 2 atomic symbol represent electron pairs in covalent bonds,
dots adjacent to only one atomic symbol represent unshared electrons
atomic symbols represent
nuclei and inner-shell electrons
dot-pairs or dashes between two atomic symbols represent
electron pairs in covalent bonds
dots adjacent to only one atomic symbol represent
unshared electrons
elements form chemical bonds because
they want to be stable
electronegativity
measure the ability of an atom in a chemical compound to attract electrons
why are there no electronegativity values given for most of the noble gases?
noble gases have outer electron shells that are already full
which element on the periodic table is the most electronegative
flourine
electronegativity difference for ionic bonds
>1.7
electroneg. difference for polar covalent bonds
1.7~0.3
electroneg. difference for non-polar covalent bonds
<0.3
ionic bond
attraction between cations and anions; cations adhere to anions because of opposite charges
one of the particles exhibit enough electronegativity to "pull" and electron from another particle
ionic bond
in ionic bonds ions minimize their potential energy by combining an orderly arrangement known as
crystal lattice
covalent bond
atoms share electron pair between two atoms;
occurs because neither of the particles are electronegative enough to be able to actually take an electron away from the other
polar covalent bond
covalent bond where bonded atoms have unequal attraction for shared electrons
non-polar covalent bond
electrons are shared equally
how are covalent bonds formed
as atoms near each other, the nuclei and electrons are attracted to each other, which corresponds in a decrease in the potential energy
metallic bond
results from attraction between metal atoms and the surrounding "sea" of electrons
how to metallic bonds get their properties
within a metal, the vacant orbitals in the atoms' outer energy levels overlap, which allows the outer electrons of the atoms to roam freely throughout the entire metal (sea of electrons)
list some characteristics of metals
malleability, ductility, heat and electrical conductivity
a bond formed between and metal and a ______ is generally classified as ionic. an example of this would be the bond formed between lithium and flourine.
nonmetal
in an ionic bond the electrons are _____ between atoms
attracted
a bond formed between a nonmetal and a ______ is generally classified as covalent
nonmetal
the bond could be classified as ______ covalent if the electrons are shared equally. an example of this would be the bond formed between two nitrogen atoms
non polar
the bond would be classified as _____ covalent if the electrons are shared unequally. an example of this would be the bond formed between hydrogen and chlorine
polar
______ bonds are found only in pure metal elements and consists of positively charged ions surrounded by a _____ of electrons
sea
this "sea" of electrons is free to move throughout the entire sample. this freedom of movement gives metals their basic physical characteristics such as
malleability, ductility, electrical and heat conductivity
single bond
a covalent bond in which one electron pair is shared by two atoms
double bond
a covalent bond where two electron pairs are shared by two atoms
triple bond
a covalent bond where three electron pairs are shared by two atoms
bond polarity
the degree to which bonding between the atoms of two elements is ionic or covalent; can be estimated by calculating the difference in the elements' electronegativities
ionic bonds vs molecular bonds
ionic- force that holds ions together is strong (attraction between + and - charges)
-strong attraction forces= higher melting and boiling points
-hard but brittle (large buildup of repulsive forces)
-does not vaporize at room temperature
molecular- force
electronegativity patterns
tend to decrease down a group or remain about the same; increases (usually) across each period;
nitrogen, oxygen, and halogens are very electronegative;
where is the lowest and highest values of electronegativity
lowest- elements in the lower left of the periodic table
highest- elements in the upper right of the periodic table
electronegativity
measure of the ability of an atom in a chemical compound the attract electrons
solubility rules
like dissolves like;
non-polar dissolves non-polar, polar dissolves polar
elements with a higher electronegativity ____ electrons; has a partial ____ charge
pulls electrons;
has a partial negative charge
a molecule is a polar if
there are lone pairs of the central atom;
or if the attached atoms are different
a molecule is non-polar if
the attached atoms are all the same
lewis dot structures show ____ electrons
valence
although xenon is a noble gas, it forms a compound with _____
flourine
groups 1 (alkali metals) and 2 (alkali earth metals) will only show "_" cloud electrons
s
groups 13~17 will show "_" and "_" cloud electrons
s, p
elements in period __ have the capacity to shift electrons into the d orbital and form bonds exceeding the normal octet rule
3; the may form bonds with 10+ electrons when they exceed the normal octet
exceptions to octet rule
hydrogen (2 electrons), boron (6 electrons), beryllium
structural formula
indicates kind, number, arrangement, and bonds but NOT the unshared pairs of atoms in a molecule;
in contrast to lewis structures
multiple covalent bonds-atoms of some elements, especially ____, ____, ____, can share more than 1 electron pair (elements)
carbon, nitrogen, and oxygen
resonance structures
refers to bonding in molecules or ions that cannot be correctly represented by a single lewis structure
the stability of molecules exhibiting resonance is more/less stable than molecules exhibiting a single resonance structure
more
polyatomic ions
charged group of covalently bonded atoms;
combine with ions of opposite charges to form ionic compounds
ionic bonding
ionic compound is composed of + and - ions that are combined so that the numbers of positive and negative charges are equal
VSEPR
(valence shell electron pair repulsion);
repulsion between pairs of valence electrons of the atoms in a molecule;
the repulsion cause these sets to be oriented as far apart as possible
list the bond angle, # of atoms bonded to central atom, and # of lone pairs on central atom for these shapes... linear, trigonal planar, tetrahedral, trigonal pyramidal, bent, and trigonal bipyramidal
linear- 180, 2, 0
trigonal planar- 120, 3, 0
tetrahedral- 109.5, 4, 0
trigonal pyramidal- 107, 3, 1
bent- 104, 2, 2
trigonal bipyramidal- 120/90, 5, 0
VSEPR theory postulates that the lone pair occupies more/less space than the bonding pairs of electrons occupy
more
hybridization
mixing of two or more orbitals of similar energies on the same atom to produce new orbitals of equal energies
hybrid orbitals
orbitals of equal energy produced by combination of two or more orbitals of the same atom
intermolecular forces
electrical forces that exist between molecules that would cause one molecule to influence another;
forces of attraction that exists between molecules in a compound
solid
matter is not compressible nor does it flow
liquid
matter is not compressible but flows
gas
matter is compressible and can flow
melting point
temperature at which a compound turns from a solid to a liquid or a liquid to a solid
boiling point
temperature at which a compound turns from a liquid to a gas or a gas to a liquid; good measure of the forces of attraction between molecules as molecules separate from one another
when substances ___, the particles are still close to one another but the fores of attraction that held the particles together in the solid state has been sufficiently overcome to let the particles move
melt
when substances ___, the particle are completely separated from one another and the attraction between molecules are completely overcome
boil
endothermic
energy is required (into system) taking in heat;
ex: ice melting, makes surrounding colder;
energy + ice = water
exothermic
energy is released;
gives off heat;
energy + water = vapor (combustion)
as the size of halogens increase, the melting and boiling points
increase
london dispersion
forces that exist between molecules as a result of positive nuclei of one molecule attracting the electrons of another molecule;
responsible for increase in melting points and boiling points of non-polar covalent compounds;
all molecular substances exhibi
dipole-dipole
forces that exist between polar molecules where the positive end of one molecule attracts the negative end of the other;
2nd strongest;
created by equal but opposite charges that are separated by a short distance
hydrogen bonding
forces that exist between molecules that have a hydrogen atom bonded to a highly electronegative atoms such as oxygen, nitrogen, or flourine;
represents a stronger dipole that will have the hydrogen end (+) attract the negative end (O, N, or F); strongest
hydrogen bonding is represented by
dotted lines
ion-ion
forces between ions and represent the strongest interparticle forces between two compounds
determine type of intermolecular forces?;
polar: yes= ____
no: H- O, N, F? yes= ____; no=____
london dispersion
hydrogen bonding
dipole-dipole
similar in size=similar ____ forces
similar london forces
given the same size, polar (dipole, hbond) covalent molecules have stronger/weaker forces of attraction than non-polar covalent molecules (london)
stronger
properties of a liquid; all properties are greater for polar molecules since their IMFs are greater than nonpolar IMFs; surface tension
resistance to an increase in its surface area;
high surface tension=high IMFs;
molecules are attracted to each other;
a molecule in the interior of a liquid is attracted by the molecules surrounding it, whereas the molecules at the surface of a liquid is
capillary action
spontaneous rising of a liquid in a narrow tube;
adhesive forces between molecules and glass overcome the cohesive forces between the molecules themselves;
the narrower the tube and the more surface area of glass, the higher the column of water climbs;
we
example of capillary action
water has higher attraction for glass, so the meniscus is concave, but Hg has higher attraction for other Hg molecules so the meniscus is convex
viscosity
resistance to flow (molecules with large intermolecular forces);
increases with molecular complexity (long chains get tangled);
increases with increasing IMFs;
ex: glycerol has 3 OH groups which have a high capacity of H bonding so this molecule is small
gases- ___IMFs; ___ motion
solids- ___IMFs; ___ motion
liquids- ___IMFs; ___ motion
gases- low IMFs; lots of motion
solids- very high IMFs; no motion
liquids- strong IMFs; some motion
lattice
3D system of points designating the centers of components (atoms, ions, molecules) that makes up the substance
network covalent
ex: carbon in diamond form (each molecule is covalently bonded to each neighboring C with tetrahedral arrangements)
ionic salt crystal lattice
square shaped
ice (holes in ice)
notice the "holes" in the hexagonal structure;
holes-makes ice less dense than liquid, allows it to float
characteristics of metals
conduct heat and electricity, are malleable and ductile;
these facts show that bonding in metals is both stron and non directional;
difficult to separate atoms, but easy to move them provided they stay in contact with each other
electron sea model
regular array of metals in a "sea" of electrons