Chapter 3 Flashcards
What are chemical bonds?
forces that hold atoms together
What will atoms aim to do as they bond?
position themselves to reduce/minimize their overall energy by filling their outer shell
What are the types of chemical bonds?
ionic, nonpolar covalent, and polar covalent
What is electronegativity?
atom’s ability to attract electrons to itself
If the electronegativity difference is less than 0.4, what type of bond is it?
nonpolar covalent
if the electronegativity difference is between 0.4 to 1.7, what type of bond is it?
polar covalent
If the electronegativity difference is greater than 1.7, then what type of bond is it?
ionic
When does ionic bonding happen?
forms between oppositely charged ions with metals and nonmetals
What is the “formula unit” ?
NaCl
How is the bonding strength for ionic compounds?
it is very strong and they are not easy to separate
How is the melting point for ionic compounds?
the melting point is very high
How is the conductivity of electricity for ionic compounds?
low as solids and high when dissolved in water or melted
What is bond energy?
measure of chemical’s bond strength
in the bond energy equation, what does E represent?
energy in joules
In the bond energy equation, what does r represent?
distance from ions in nm
In the bond energy equation, what does Q1 and Q2 represent?
charges of the ions
What do atoms seek to do in terms of configuration?
they seek to do a noble gas configuration
In group 1A, do atoms lose or gain electrons?
they lose 1 electron
In Group 2A, do atoms lose or gain electrons?
they lose 2 electrons
In group 3A, do atoms lose or gain electrons?
they lose 3 electrons
In Group 6A, do atoms lose or gain electrons?
they gain 2 electrons
In group 7A, do atoms lose or gain electrons?
they gain 1 electrons
When predicting the formulas for ionic compounds, what must you consider?
1) consider a number of valence electrons for both atoms
2) consider atom’s electronegativity (non-metals are more electronegative)
3) chemical compounds are always electrically neutral
What is covalent bonding?
when electrons are shared between atoms
Why do covalent bonds happen?
if the energy of the electrons in hydrogens are lower, for example, they tend to share since the electrons are attracted towards a positive charge
What does — represent in bonding?
sharing of electrons
What is the bond length?
distance between two atoms where energy is lowest (aka smallest distance) and it happens with two or more NON-METALS
What is the bond strength of covalent compounds?
weaker and requires less energy to break
How is the melting point for covalent compounds?
low melting point (like sugar)
How is the conductivity of covalent compounds?
very poor and poor in water as well
What are polar covalent bonds?
when there is an unequal sharing between atoms in a molecule and they is not enough energy to split
The more electronegative atom in a polar covalent bond has what partial charge?
negative
The less electronegative atom in a polar covalent bond has what partial charge?
positive
What is the driving force for bonding?
energy
What is the localized electron model?
assumes that molecules are composed of atoms that are bound together by sharing pairs of electrons
What are lone pairs?
electrons that are localized on an atom, usually in two pairs
What is a bonding pair?
electrons found in the space between the atoms in a bond
What are the parts of the localized electron model?
a) using Lewis structures to describe valence electrons only in an arrangement in the molecule
b) using VESR to predict the geometry of molecules (in the 4th chapter)
c) describing orbitals used by atoms to share electrons or hold lone pairs
For Lewis Dot Structures, what is the main goal?
atoms achieving noble gas configurations
What do Lewis Dot Structures show?
valence electrons in a molecule
How do you write Lewis Dot Diagrams for ionic compounds?
with brackets, subscripts, and their ionic charge (practice with problems)
How do you draw Lewis Dot Diagrams?
a) figure out the sum total number of valence electrons from all atoms
b) use pairs of electrons to form bond between pairs of bound atoms
c) arrange remaining electrons to satisfy duet/octet rule
What is the octet rule?
elements form stable molecules when surrounded by 8 valence electrons
What is the duet rule?
hydrogen atoms have no more than 2 electrons in their valence shells
How do you know which one is the central atom?
it is 99% depicted first in the compound and they like symmetry
What element is an exception to the octet rule?
boron because it tends to form 3 covalent bonds
In terms of periods, what is an exception for the octet rule?
the octet rules only applied for periods three and beyond
How do you form lewis structures for an odd amount of valence electrons?
have the more electronegative atom with more electrons
When does resonance occur?
when there are multiple valid Lewis structures that can be written for a single molecule
What are the rules of resonance?
1) all atoms must be connected in the same order
2) resonance is represented by double-headed arrows
What are formal charges?
charges assigned to an atom in a molecule which are made up
What are the assumptions for formal charges?
1) lone electrons pairs belong to the atom in question
2) bonding electron pairs are shared between two atoms
What is the equation for formal charges?
FC= V - N -B
What does FC stand for in the formal charges equation?
formal charge
What does V stand for in the formal charges equation?
number of valence electrons of a particular atom
What does N stand for in the formal charges equation?
number of nonbonding electrons (aka the lone pairs)
What does the B stand for in the formal charges?
number of bonds that particular atom makes
What do atoms in molecules prefer as their formal charge?
to be 0 or close to 0
Where should the negative formal charges reside in a molecule?
on the more electronegative atoms
What is a binary compound?
contains 1 metal and 1 nonmetal
How do you name a binary compound in general?
name the cation first as its normal form, then the name of the anion comes next and contains the suffix “ide” at the end (ex: MgO is magnesium oxide)
When do you add roman numerals to the name of a compound?
when there is a transition metal or a metal that can exist as more than 1 ion (like Fe can be 2+ or 3+ )
How do you name a binary compound that contains an ion that can be in many forms?
identify the charge on the metal and put it in roman numerals, then name the nonmetal as normal (ex: FeO is iron (II) oxide)
What is the polyatomic ion for mercury (I)?
2+
Hg
2
What is the polyatomic ion for ammonium?
+1
NH
4
What is the polyatomic ion for nitrate?
1-
NO
3
What is the polyatomic ion for nitrite?
1-
NO
2
What is the polyatomic ion for sulfate?
2-
SO
4
What is the polyatomic ion for sulfite?
2-
SO
3
What is the polyatomic ion for hydrogen sulfate?
-1
HSO
4
What is the polyatomic ion for hydroxide?
-1
OH
What is the polyatomic ion for cyanide?
1-
CN
What is the polyatomic ion for phosphate?
3-
PO
4
What is the polyatomic ion for hydrogen phosphate?
2-
HPO
4
What is the polyatomic ion for dihydrogen phosphate?
1-
H PO
2 4
What is the polyatomic ion for thiocyanate?
- -
NCS or SCN
What is the polyatomic ion for carbonate?
2-
CO
3
What is the polyatomic ion for hydrogen carbonate?
1 -
HCO
3
What is the polyatomic ion for chlorate?
1 -
ClO
3
What is the polyatomic ion for chlorite?
1-
ClO
2
What is the polyatomic ion for hypochlorite?
1 - 1-
ClO or OCl
What is the polyatomic ion for perchlorate?
1-
Cl
4
What is the polyatomic ion for acetate?
1-
C H O
2 3 2
What is the polyatomic ion for permanganate?
1-
MnO
4
What is the polyatomic ion for dichromate?
2-
Cr O
2 7
What is the polyatomic ion for chromate?
2-
CrO
4
What is the polyatomic ion for peroxide?
2-
O
2
What is the polyatomic ion for oxalate?
2-
C O
2 4
What is the polyatomic ion for thiosulfate?
2-
S O
2 3
How do you name covalent compounds?
1) first element is named
2) second element contains suffic “ide”
3) use prefixes to denote number of atoms present
What types of atoms are in covalent compounds?
two nonmetals
How do you name a substance that as H+ attach to an anion (aka nonmetal)?
1) if the anion ends in -ide, acid is named w/ hydro- and -ic (HCl is hydrochloric acid)
2) if anion ends in ate, suffc -ic added to a root name (H2SO4 is sulfuric acid)
3) if anion ends in -ite, it is replaced by -ous (H2SO3 is sulfurous acid)
What is the equation for bond energy?
E = (2.31x10^23 Jxnm) ([Q1-Q2]/r)
How many bonds does boron have?
3 separate bonds
What happens when the amount of electrons exceeds the octet rule?
you put the rest of the electrons in the central atoms
What happens to the compounds with an odd number of electrons?
electrons go to the more electronegative atom
List in increasing polarity O -O O - H S - H H - F C - Cl
O - O S - H C - Cl O - H H - F
What are major contributors?
one has lowest energy (get it from formal charges equations for each type of atom involved)
Finish the sentence: Ionic compounds are comprised of ……
Ionic compounds are comprised of many interactions between ions