Chemistry Test - Bonding
covalent (molecular) bonds
sharing of electrons -nonpolar covalent bonds -multiple covalent bonds -polar covalent bonds -coordinate (dative) covalent bonds -network solid
molecule
smallest discrete particle of an element or compound formed by covalently bonded atoms
how are bonds formed?
spontaneously (do not require energy, exothermic, energy is released (BARF) A+B -> AB + heat
using SNAP to determine molecule polarity
symmetrical shape = nonpolar, asymmetical shape = polar (SN AP)
metallic bonds
"sea of mobile electrons"
Noble gases
A majority of them have 8 electrons in the valence shell
polar bonds don't mean polar molecule because
in order to determine polarity of a MOLECULE the shape must be determined (SNAP)
bonds between a polyatomic ion and another ion is
ionic (ex CO₃²- and Ca²+)
why are ionic substances only good conductors when melted or dissolved in water?
just like metals are good conductors if they have mobile electrons, a substance/solution is a good conductor if there are moble ions -in a solid, the ions in an ionic substance are unable to move because the ions are rigid and crystalline -in a liquid or when dissolved in water, the ions in an ionic substance are mobile
network solid
macromolecule formed by covalent bonds between atoms in a continuous network
dipole moment
measure of the strength of the dipole within a molecule (i.e polarity)
Duet rule
Hydrogen can only go to a max of 2 electrons to become stable
examples of molecular elements
H₂, O₂, N₂
asymmetrical (polar) molecules
H₂O (bent V), NH₃ (trigonal pyramid), HCl
examples of molecular compounds
H₂O, CO₂, NH₃, CCl₄, and HCl
substances like ___ ___ __ and __ have relatively high boiling point due to strong hydrogen bonding
H₂O, HF, and NH₃
substances with strong hydrogen bonds
H₂O, NH₃, HF
what types of molecules display partial positive and partial negative charges in diff regions of the molecule?
molecules that have an uneven distribution of charge (either due to unequal EN or asymmetrical shape which leads to polar molecule)
which group 16 element combines with hydrogen to form a compound that has the strongest hydrogen bonding between its molecules? 1. oxygen (END: 1.2) 2. selenium (END: 0.4) 3. sulfur (END: 0.4) 4. tellurium (END: 0.1)
oxygen because it has the highest END
compounds that contain both covalent and ionic bonds will contain a
polyatomic ion
the (greater/less) the energy released during the formation of a bond, the (more/less) stable the resulting bond it
the greater the energy released during the formation of a bond, the more stable the resulting bond is
hydrogen bond strength rule
the higher the END between the element and hydrogen, the stronger the hydrogen bond
rule for London dispersion forces & electron & strength & frequency
the more electrons there are, the more frequent (and stronger) the London disperson forces
molecules composed of only 2 atoms (diatomic) such as H₂ or HCl polarity rule
the polarity of the bond = the polarity of the molecule
dipole-dipole forces
result from the temporary attraction of the positive region (or pole) of one molecule to the negative region (or pole) of another molecule
coordinate dative bonds
formed between two atoms that share a pair of electrons that are provided entirely by one of the atoms but are shared by both (ex: NH₄+ and H₃O+)
metallic bond
formed by the force of attraction of a single metal's mobile valence electrons for an atom's positively charged kernel (nucleus + kernel electrons)
END relating to polarity/ dipole moment rule
greater END = greater polarity/ dipole moment
greater END = greater polarity/ dipole moment =
greater strength of the IMFs in the molecule
the stronger the intermolecular forces in a substance, the __ the boiling point of the substage
higher (stronger IMFs - higher boiling points)
in a polar molecule (partialness relating to EN)
higher END = partial negative lower END = partial positive
"the sea of mobile valence electrons" **METALLIC BONDING**
highly mobile valence electrons --> good electrical + thermal conductivity for metals
has the largest effect on boiling point of a substance as it is the strongest IMFs
hydrogen bonding
molecules composed of more than 2 atoms such as CO₂, H₂O and NH₃ polarity rule
the polarity of the bond CAN DIFFER from the polarity of the molecule (remember SNAP)
why are IMFs considered weak?
the strongest IMFs are less than 5% as strong as the bonds between atoms
ionic bonds
transfer of electrons
London dispersion forces
type of IMF present between atoms and nonpolar molecules; present in group 18; weakest type of IMF
polar covalent bonding
unequal sharing of electrons; unequal EN values
what causes London dispersion forces?
uneven distribution of electrons in an atom or nonpolar molecule at any given time
Compound
A chemical combination of two or more elements in a definite or fixed ratio
most important example of hydrogen bonding
-H₂O; responsible for the relatively high boiling point of water (100ºC) of
lewis electron-dot diagrams
-diagram will be drawn differently if ionic or covalent bond -ionic: consist of lewis electron dot diagrams for the ions formed by the loss and gain of electrons -covalent: consist of lewis electron dot diagrams for the atoms that form the bond -if there are more than two atoms, the atom in the center is the atom with multiple unpaired valence electrons -every bond (2 electrons) can be replaced with a long dash
important things to remember when drawing lewis electron dot diagram of ionic
-don't forget to cross if not charges aren't equal -when charges are equal, the first element electron's is 0 and the 2nd is 8 -when elements both have subscripts, use coefficients -pay attention to charges ( YOU DONT EVER CHANGE CHARGES) -pay attention to electron configuration
bond with smallest END
-least polar (most nonpolar) -highest covalent character
ionic bonding
-metal (+) loses e- to a nonmetal (-) -metal (+) combines with a polyatomic ion (-) -polyatomic ion (+) combines with a nonmetal (-) -polyatomic ion (+) combines with polyatomic ion (-) (BASICALLY IONIC & IONIC or IONIC & COVALENT)
properties of bonds
-metallic bonds are good conductors because they have mobile valence electrons -the only metallic liquid is mercury (Hg), mercury is an exception because it has no high melting point -water, a covalently bonded molecule, makes a SPLash (soft, poor conductors of heat & electricity, low melting & boiling points) METALLIC BONDING is the complete opposite (HGH, high melting and boiling points, good conductors of heat & electricity, hard)
bond with largest END
-most polar (least nonpolar) -highest ionic character
drawing diatomic elements lewis electron dot diagram
-non polar covalent -trick: how every many electrons are missing from the valence shell, is the number of bonds (THIS ONLY WORKS FOR DIATOMIC)
covalent bonding
-nonmetal shares electrons with another nonmetal -diatomic molecules (BrINClHOF) (BASICALLY A NONMETAL & NONMETAL)
electronegativity difference between the 2 atoms involved in a bond can shed light on the bond type
-nonpolar covalent: END typically between 0 and 0.3 -polar covalent: END Typically between 0.3 and 1.7 -ionic: END typically greater than or equal to 1.7
hydrogen bonding
-type of intermolecular bond between a hydrogen atom in one molecule and a nitrogen, oxygen or fluorine atom in another molecule (REMEMBER FON) -strongest type of IMF
3 types of IMFs
1. hydrogen bonding (NOT A BOND) *strongest* 2. dipole-dipole forces 3. London dispersion/ vander Waals
3 major types of bonds
1. ionic bonds: transfer of electrons 2. covalent (molecular) bonds: sharing of electrons 3. metallic bond: "sea of mobile electrons"
exceptions to END rules
1. metal hydrides(metal + hydrogen)--> ionic -metal and nonmetal= ionic -ex: NaH: 2.2-0.9= 1.3 (1.3 is in the polar covalent range but its ionic), LiH -END values may be lower than 1.7 (covalent range), but the bond is ionic 2. hydrogen monofluoride (HF) -> covalent -2 different nonmetals are covalent -END values of 1.8 (ionic range), but the bond is covalent 3. AlCl₃ -> ionic -END is 1.6 (covalent range) but the bond is ionic
types of covalent bonding
1. non polar: formed between atoms having equal or close EN values, equal sharing of electrons (EX: DIATOMIC MOLECULES) 2. polar: formed between atoms having unequal EN values, unequal sharing of electrons (EX: H₂O, HCl, NH₃) POLAR BEARS LIKE WATER 3. multiple: atoms that share more than one pair of electrons (double or triple bonds) (EX: O₂, N₂, CO₂) 4. coordinate (dative): formed between two atoms that share a pair of electrons that are provided entirely by one of the atoms but are shared by both (EX: NH₄+, H₃O+) 5. network solid: macromolecule formed by covalent bonds between atoms in a continuous network (EX: diamond, graphite, silicon, carbide (SiC), silicon dioxide (sand, SiO₂)
1 bond has 1 pair of electrons, so there are __ electrons
2
which of the following compounds has the strongest intermolecular forces? 1. HCl -> dipole moment of 1.08 2. HF -> dipole moment of 1.82 3. Hl -> dipole moment of 0.44 4. HBr -> dipole moment of 0.82
2. HF because it's greatest dipole moment of 1.82
Octet rule
Atoms bond together to achieve stability by having 8 valence electrons
How does an atom become stable?
By achieving an octet through gaining, losing or sharing electrons
Reaction 1: X + Y -> XY + 750 joules Reaction 2: E + F -> EF + 400 joules Reaction 3: CD + 0.8KJ -> C + D which product is more stable? and why?
CD is more stable because you can reverse it if a bond is not being formed CD + 0.8KJ -> C + D can be C+ D -> CD + 0.8KJ
symmetrical (nonpolar) molecules
CO₂ (triatomic, linear), CH₄ (tetrahedral), H₂ (diatomic)
more examples of ionic and covalent bonds
CaCO₃ (metal + polyatomic ion) NH₄Cl (polyatomic ion + nonmetal) NH₄NO₃ (polyatomic ion + polyatomic ion)
Bond
Force of attraction between two atoms which are formed as the result of a chemical reaction
which substances in the table below has the strongest intermolecular forces? ** pay attention to boiling points HF- 293 K HCl- 188 K HBr- 207 K Hl- 237K
HF
intermolecular forces (IMFs)
NOT BONDS; weak forces that act between molecules and hold them together
how are bonds broken?
NOT spontaneously (do require energy, endothermic, energy is absorbed) (BARF) AB + heat -> A + B
examples of ionic bonding
NaCl, CaSO₄, NH₄Cl, NH₄NO₃
which of the following compound contains both covalent and ionic bonds? NaCl NH₄+ MgSO₄ H₂O
NaCl: ionic NH₄+: covalent MgSO₄: ionic and covalent (because there are covalent bonding between atoms in polyatomic ions) H₂O: covalent
which of the following bonds is the most polar (largest END) in nature? (Table S) O₂, HCl, NH₃, HBr
O₂: 3.4 -3.4= 0 : a nonpolar covalent bond HCl: 3.2- 2.2= 1.0 : a polar covalent bond NH₃: 3.0-2.2= 0.8 : a polar covalent bond HBr: 3.0-2.2= 0.8: a polar covalent bond *note: when finding END, do not use subscript unless its diatomic
Valence electrons
Participate in bonding
Octet
Represents the maximum number of valence electrons that an atom can have (8)
examples of covalent bonding
SO₂, HCl, H₂O, Cl₂ (and all diatomic molecules: Br₂, I₂, N₂, Cl₂, H₂, O₂, F₂)
strongest type of London dispersion forces
Van der Waals forces
Reaction 1: X + Y -> XY + 750 joules Reaction 2: E + F -> EF + 400 joules which product is more stable? and why?
XY is more stable because 750 > 400, more energy was released
which of the following contains metallic bonding? MgCl₂ O₂ Zn NaNO₃
Zn (metallic bonds take place inside a single metal)
what kind of attraction exists between dipoles in London dispersion forces?
a temporary one
uneven distribution of electrons found in London dispersion forces creates
a weak instantaneous dipole
multiple covalent bonding
atoms that share more than one pair of electrons (double or triple)
there is a connection between IMFs present in a substance and the substance's
boiling point
bonds between atoms in a polyatomic ion is
covalent (ex: CO₃²-)
why are covalent substances always poor conductors?
covalent (made of 2 nonmetals and they share electrons )substances are not composed of ions
molecules generally have properties associated with
covalent bonding (SPLash)
IMFs only exist in __ bonded molecules
covalently
non polar covalent bonding
equal sharing of electrons; equal/ close EN values
molecular substances may exist as solids, liquids or gases depending on the strength of the ____
force of attraction between the molecules
coordinate (dative) bonding
formed between two atoms that share a pair of electrons that are provided entirely by one of the atoms but are shared by both