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Level 164

Bonding & Lewis Structures


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Non-polar Covalent
A covalent bond, usually between diatomic molecules, that has an overall electro-negativity of less than 0.3. Oxygen, Nitrogen, Flourine, Chlorine, Bromine, Iodine, and Hydrogen are perfect examples.
polar covalent
<| en 0.4-1.9
ionic bonds
form from the attraction of oppositely charged ions.
covalent bonds
atoms share pairs of electrons
molecular geometry
geometrical arrangement of atoms in a molecule
tetrahedral
3 dimensional shape showing one central atom with 4 atoms coming off of it. Tetra means four!
Linear
2 Bonds
H2O
Bent (or) Angular
NH3
Ammonia
Bond Dissociation Energy
Energy required to break a covalent bond
molecule
2 or more atoms of same or different kinds that are chemically combined.
Molecular formula
not the lowest whole # but the actual #of atoms of each element present
-2 or more nonmetals
Properties of a covalent bond
Diatomic molecules
a molecule of 2 identical atoms
octet rule
a concept of chemical bonding theory that is based on the assumption that atoms tend to have either empty valance shells or full valence shells of eight electrons
Single bond
1 pair of shared electrons
double bond
2 atoms share 4 electrons (2 pairs)
triple bond
2 atoms share 6 electrons (3 pair)
coordinate baond
1 atom contributes both bonding atoms
C rule
if C is there than c is in the middle b/c it wants 4 electrons
Polyatomic Ions
A group of atoms covalently bonded together which together have a charge that comes from either gained or lost electrons to gain an octet
resonance structures
Sometimes a single Lewis structure is inadequate to represent a particular molecule (or ion). In such situations, we describe the molecule by using two or more _______ for the molecules.
exceptions to Octet Rule
Cannot be satisfied in molecules whose total number of valence electrons is an odd number.
Naming acids
If ends with ide hydro+root+ic acid
Structural formula
A structural formula shows the connectivity of the atoms in the molecule.
lone pair
a _______ (or non bonding electron air) occupies more apace than a bonding pair
Chemical Bond
An attractive force that holds together the atoms, ions, or groups of atoms in a molecule or compound.
Lewis Structure
_______ shows valence electrons
atomic symbols represent
nuclei and inner-shell electrons
electron pairs in covalent bonds
dot-pairs or dashes between two atomic symbols represent
unshared electrons
dots adjacent to only one atomic symbol represent
elements form chemical bonds because
they want to be stable
Electronegativity
a measure of the ability of an atom in a chemical compound to attract electrons
noble gases have outer electron shells that are already full
why are there no electronegativity values given for most of the noble gases?
flourine
which element on the periodic table is the most electronegative
>1.7
electronegativity difference for ionic bonds
1.7~0.3
electroneg. difference for polar covalent bonds
<0.3
electroneg. difference for non-polar covalent bonds
Ionic Bond
a bond that results from electrostatic attraction between oppositely charged ions. The cation is positively charged, while the anion is negatively charged.
crystal lattice
a 3-D system of points designating the centers of components that make up the substance
Covalent bond
a bond formed when atoms share one or more pairs of electrons
polar covalent bond
a covalent bond in which a shared pair of electrons is held more closely by one of the atoms
non-polar covalent bond
a covalent bond in which the bonding electrons are shared equally by the bonding atoms, resulting in balanced distribution of electrical charge
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
a bond formed by the attraction between positively charged metal ions and the electrons around them
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
nonmetal
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.
attracted
in an ionic bond the electrons are _______ between atoms
non polar
A non-polar molecule is a molecule which shares electrons equally and therefore, lacks oppositely charged ends
polar
a molecule in which the centroid of the positive charges is different from the centroid of the negative charges.
sea
_______ bonds are found only in pure metal elements and consists of positively charged ions surrounded by a _______ of electrons
malleability, ductility, electrical and heat conductivity
this "sea" of electrons is free to move throughout the entire sample. this freedom of movement gives metals their basic physical characteristics such as
Bond polarity
In covalent bonds, the electrons may not necessarily be shared equally between two atoms. _______helps describe unequal sharing of electrons in the bond.
ionic bonds vs molecular bonds
ionic- force that holds ions together is strong (attraction between + and - charges)
electronegativity patterns
tend to decrease down a group or remain about the same; increases (usually) across each period;
where is the lowest and highest values of electronegativity
lowest- elements in the lower left of the periodic table
solubility rules
like dissolves like;
pulls electrons;
elements with a higher electronegativity _______ electrons; has a partial _______ charge
a molecule is a polar if
there are lone pairs of the central atom;
a molecule is non-polar if
the attached atoms are all the same
valence
lewis dot structures show _______ electrons
s
Speed (variable)
s, p
groups 13~17 will show "_" and "_" cloud electrons
3; the may form bonds with 10+ electrons when they exceed the normal octet
elements in period __ have the capacity to shift electrons into the d orbital and form bonds exceeding the normal octet rule
carbon, nitrogen, and oxygen
multiple covalent bonds-atoms of some elements, especially _______, _______, _______, can share more than 1 electron pair (elements)
Ionic bonding
Bonding between metals and nonmetals
VSEPR
(valence shell electron pair repulsion);
linear- 180, 2, 0
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
hybridization
a mathematical procedure in which the standard atomic orbitals are combined to form new atomic orbitals called hybrid orbitals that correspond more closely to the actual distribution of electrons in chemically bonded atoms
hybrid orbitals
_______ are eqivalent because they have the same size, shape, and energy
intermolecular forces
electrical forces that exist between molecules that would cause one molecule to influence another;
Solid
Fixed shape and size, atoms are close together, ordered structure, not compressible
Liquid
No fixed shape or size, no long-range order, assume shape of container, fixed volume, not compressible
Gas
matter that does not have a definite shape or volume
melting point
temperature at which a compound turns from a solid to a liquid or a liquid to a solid
Boiling Point
??T bp = Kbp • m • i
melt
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
boil
when substances _______, the particle are completely separated from one another and the attraction between molecules are completely overcome
endothermic
A chemical reaction that absorbs heat
exothermic
A chemical reaction that releases energy
increase
as the size of halogens increase, the melting and boiling points
london dispersion
forces that exist between molecules as a result of positive nuclei of one molecule attracting the electrons of another molecule;
dipole-dipole
forces that exist between polar molecules where the positive end of one molecule attracts the negative end of the other;
hydrogen bonding
- the force of attraction between the hydrogen atom of one molecule and an unshared electron pair on F, O, or N
dotted lines
hydrogen bonding is represented by
ion-ion
forces between ions and represent the strongest interparticle forces between two compounds
similar london forces
similar in size=similar _______ forces
stronger
given the same size, polar (dipole, hbond) covalent molecules have stronger/weaker forces of attraction than non-polar covalent molecules (london)
resistance to an increase in its surface area;
properties of a liquid; all properties are greater for polar molecules since their IMFs are greater than nonpolar IMFs; surface tension
capillary action
attraction of the surface of a liquid to the surface of a solid
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
friction or resistance to motion when molecules move past each other in a liquid
liquids- _______IMFs; _______ motion
gases- low IMFs; lots of 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)
square shaped
ionic salt crystal lattice
ice (holes in ice)
notice the "holes" in the hexagonal structure;
characteristics of metals
conduct heat and electricity, are malleable and ductile;
electron sea model
regular array of metals in a "sea" of electrons