Chemistry Ch 4
hydronium, ammonium, and hydroxide ions have, respectively, the chemical formulas...
(H_3O)+, (NH_4)+, and (OH)-
the nitrate, sulfate, and phosphate ions have, respectively, the chemical formulas...
(NO_3)-, (SO_4)2-, and (PO_4)3-
naming AuCl
*Au can have a variable charge -(gold charge) + (chlorine charge) = 0 -chloride ion has a 1- charge (in group VIIA), so gold must need a 1+ charge to equal zero -name = gold (I) chloride
write chem formula for NH^4+ and CN-
-both have opposite charges of one -NH_4CN
name Ca_3(PO_4)_2
-calcium is a fixed charge metal so no roman numeral is needed -calcium phophate
the charge of an ion
-depends on # of electrons lost/gained -loss of one, two, three = +1, +2, +3 -gain of one, two, three = -1, -2, -3 ***charge is noted as a superscript placed to right of chemical symbol
ionic compounds
-ionic bonds are present -composed of cations and anions -high melting pts -good conductors of electricity when in liquid state or in a solution -do not have molecules as basic structural unit; ions are the structural unit
determine chemical formula for magnesium fluoride
-magnesium is in group IIA (2 valence electrons), forms a 2+ ion -fluorine is in group VIIA (7 valence electrons), forms a 1- ion -MgF_2
determine chemical formula for tin (IV) oxide
-tin = 4+ ion -oxygen is in group VIA (6 valence electrons), forms a 2- ion -SnO_2
write chem formula for Mg^2+ and (NO_3)-
-two nitrate ions (1- charge) are required to balance the charge on one magnesium (2+ charge) -Mg(NO_3)_2
write chem formulas for Na+ and (SO_4)2-
-two sodium ions are needed (1+) charge for each sulfate (2-) charge - Na_2SO_4
the outermost electron shell is also called the...
...valence electron shell
molecular compounds
A compound consisting of molecules of covalently bonded atoms -lower melting pts -tend to be gases, liquids, or low-melting pt solids -do not conduct electricity in molten state
what is the chemical formula for a compound that contains Al^3+ ions and OH- ions?
Al(OH)_3
what is the correct chemical formula of the ionic compound formed when Al^3+ ions and S^2- ions combine?
Al_2S_3
1. what is the chemical formula for a compound that contains K+ ions and (PO_4)3- ions?
K_3PO_4
when magnesium (2 valence electrons) combines with chlorine, (7 valence electrons), the resulting ionic compound has the chemical formula...
MgCl_2
valence electron
an electron in the outermost electron shell of a representative element or noble-gas element (always found in either s or p subshells)
the octet rule relates to the number 8 bc...
atoms, during compounds formation, frequently obtain 8 valence electrons
which of the following binary ionic compounds has a name that includes a Roman numeral? a. Na_2O b. Fe_2O_3 c. MgCl_2
b
which of the following binary ionic compounds is paired with an incorrect name? a. CaS- calcium sulfide b. K_2O- dipotassium oxide c. AlN- aluminum nitride
b
which of the following chemical formula is that of a polyatomic ion? a. Cl- b. OH- c. S^2-
b
explain why ionic compounds do not contain individual molecules
bc the array of alternating positive and negative ions present means discrete molecules don't exist -the chem formula for an ionic compound represents the RATIO of the ions present, not the groupings of ions -basic formula units are repeated indefinitely (formula unit is what chemists use instead of molecule to refer tot the smallest unit on an ionic compound)
which of the following is a characteristic of binary ionic compounds? a. two different metals are present b. two different nonmetals are present c. both a metal and a nonmetal are present
c
the structure of an ionic compound, in the solid state, involves which of the following a. individual molecules in which positive and negative ions are present b. a nonmolecular random arrangement of positive and negative ions c. a nonmolecular highly ordered arrangement of positive and negative ions
c.
which of the following is a correct description of the structure of ionic compound NaCl? a. alternating layers of Na+ and Cl- ions are present b. individual molecules containing Na+ and Cl- ions are present c. each ion present is surrounded by six ions of opposite charge
c.
which of the following is a very stable valence electron configuration? a. ns^2, np^2 b. ns^2, np^4 c. ns^2, np^6
c. ns^2, np^6
covalent bond
chemical bond formed thru the sharing of one or more pairs of electrons between two atoms
ionic bond
chemical bond formed thru the transfer of one or more electrons from on atom to another
Lewis Symbol (electron dot structures)
chemical symbol of an element surrounded by dots equal in number to the number of valence electrons present in atoms of the element
Lewis structure
combination of Lewis symbols that represents either the transfer or the sharing of electrons in chemical bonds (involve compounds)
binary compound
compound in which only two elements are present
the correct name for the binary ionic compound Cu_2S is
copper (I) sulfide
octet rule
in forming compounds, atoms of elements lose, gain, or share electrons in a way to produce a noble gas electron configuration for each of the atoms involved
polyatomic ion
ion formed from a group of atoms (held together by covalent bonds) thru the loss or gain of electrons ex: sulfate - (SO_4)^2- -very stable and generally maintain identity during chemical reactions -an ion (either positively or negatively charged) that contains more than one atom -NOT molecules, never occur alone as molecules do, always found associated w/ ions of opposite charge
monatomic ion
ion formed from a single atom thru the loss or gain of electrons (Cl-, Na+, Ca^2+, N^3-, and so on)
binary ionic compound
ionic compound in which one element present is a metal (positive) and the other element present is a nonmetal (negative)
an Al^3+ ion is an Al atom that has
lost three electrons
In terms of subatomic particles, a Ca^2+ ion contains...
more protons than electrons
pure covalent bond
neutral atoms held together by equally shared electrons -aka nonpolar covalent bond
the most stable of all valence electron configurations is that of the
noble gases
most stable electron configuration
noble gases: helium, neon, argon, krypton, xenon, and radon -posses 8 valence electrons as (ns^2, np^6) - outermost s and p shells completely filled -(except helium which is 1s^2) -unreactive -one elemental gases found in nature in form of individual, uncombined atoms (have little or no tendency to form bonds)
in forming an ionic compound from Ca (2 valence electrons) and S (6 valence electrons), how many calcium atoms are needed to meet the electron needs of on S atom?
one
electron transfer
one element (metal) gives an electron to another element (nonmetal) *no atoms can lose electrons unless another atom is available to accept them -the resulting charges = attraction between two elements = ionic compound
what is the name for the compound Na_2CO_3?
sodium carbonate
the correct name for the binary ionic compound NaF is
sodium fluoride
stable
systems of electrons does not easily undergo spontaneous change
determine the chemical formula for Be^2+ and P^3-
the #'s in the charges for these ions are 2 & 3; the lowest common multiple of 2 & 3 is 6 (2x3=6) -so we need 6 units of positive charge and 6 units of negative charge; -three Be^2+ ions = 6 units of positive charge -two P^3- ions = 6 units of negative charge -chemical formula: Be_3P_2
the number of valence electrons in a representative element can be determined from...
the atom's electron configuration (write out the electron configuration, find the highest electron shell number, and then find how many electrons are in the shell)
chemical bond
the attractive force that holds two atoms together in a more complex unit -result of interactions between electrons -nature of chemical bonds is due to electron configurations
how inner transition ion compounds are named
the charge (indicated by roman numerals) on the metal ion must be given with the name ex: FeCl_2 = iron (II) chloride (bc there needs to be a charge of 2+ on iron to complete valence shell of two chloride ions) ex: CuO = copper (II) fluoride (bc oxygen is in group VIA which means it needs two electrons, so copper must have a 2+ charge to balance)
the concept of electron sharing is closely associated with...
the covalent bond model
how binary compounds are named
the full name of the metallic element is given first, followed by a separate word containing the stem of the nonmetallic element name and suffix -ide ex: name of NaF = sodium fluoride
the concept of electron transfer is closely associated with...
the ionic bond model
determine the chemical formula for Na+ and P^3-
the ions combine in a 3-to-1 ratio bc this combo causes the charges to add to zero; three Na+ ions give 3 units of positive charge; one P^3- ion results in 3 units of negative charge; chemical formula: Na_3P
formula unit
the smallest whole number repeating ratio of ions present in an ionic compound that results in charge neutrality
t or f: atoms are seldom encountered by themselves
true -atoms are almost always found in clusters of 2 to numbers too large to count
t or f: most bonds are not 100% ionic nor 100% covalent
true -most bonds have some degree of both the transfer and sharing of electrons
t or f: electron loss always equal electron gain in an electron transfer process
true (results in a neutral ionic compound, bc the positive charge of one ion is balanced by the negative charge of the other ion)
true or false: transitional metals and inner transitional metals can form more than one type of ion
true - this is why the octet rule only applies to representative elements ex: iron (Fe) can form Fe^2+ or Fe^3+ depending on chemical circumstances
t or f: an ion that is isoelectronic with a noble gas does not have the same properties of the noble gas
true: has not been converted into noble gas, the number of protons in nucleus of isoelectronic ion is diff from that of a noble gas
in forming the ionic compound K_2O from K (1 valence electron) and O (6 valence electrons), how many electrons does each oxygen atom acquire via electron transfer?
two
ion formation through loss of electrons...
always produces a positive ion
name (NH_4)_2CO_3
ammonium carbonate (just the names of the two polyatomic ions is needed)
what is the name for the compound (NH_4)_2S?
ammonium sulfide
ion
an atom (or group of atoms) that is electrically charged as a result of the loss or gain of electrons -# of protons does not equal # of protons
isoelectronic species
an atom and an ion, or two ions, that have the same number of configuration of electrons
what is a general characteristic of most ionic compounds?
good electrical conductors in the molten state
naming Fe_2O_3
- 2(iron charge) + 3(oxygen charge) = 0 - 2(iron charge) + 3(2-) = 0 - 2(iron charge) = 6+ - iron charge = 3 - name = iron (III) oxide
name Fe_2(SO_4)_3
- 2(iron charge) + 3(sulfate charge) = 0 - sulfate charge is 2- (found on table) - 2(iron charge) + 3(2-) = 0 - 2(iron chage) = 6+ - iron charge = 3+ - iron (III) sulfate
given that Z^2- ions are present in the ionic compound X_2Z, what is the charge on the X ions present?
1+
an atom with one valence electron would most likely form a
1+ ion
the compound Mg(SCN)_2 contains Mg^2+ ions and polyatomic thocyanate ions; what charge does the thiocyante carry?
1-
rules for naming binary compounds
1. if a positive polyatomic is present, its name is substituted for that of the metal 2. if a negative polyatomic ion is present, its name is substituted for that of the nonmetal stem name and the "ide" suffix 3. if both positive and negative polyatomic ions are present, dual name-substitution occurs, and the resulting name includes just the name of the polyatomic ions
electron-loss-electron-gain behavior guidelines
1. metal atoms containing 1, 2, or 3 valence electrons (in groups IA, IIA, & IIIA) tend to lose electrons to acquire a noble-gas configuration (group IA form 1+ ions, IIA forms 2+ ions, IIIA forms 3+ ions) 2. nonmetal atoms containing 5, 6, or 7 valence electrons (nonmetals in VA, VIA, & VIIA) tend to gain electrons to acquire a noble gas configuration (group VIIA nonmetals form 1- ions, VIA nonmetals form 2- ions, and VA nonmetals form 3- ions) 3. elements in group IVA have to gain or lose 4 electrons to have noble-gas structure; theoretically, ions with charge 4+ or 4- could be formed by Carbon, but in most cases covalent bonding results
two concepts fundamental to understanding bonds:
1. not all electrons in an atom participate in bonding; those that do are called valence electrons 2. certain arrangements of electrons are more stable than others, as is explained by the octet rule
3 important generalizations about valence electrons
1. representative elements in the same group of the periodic table have the same number of valence electrons (due to their similar chemical properties/similar outer-shell electron configurations) 2. the number of valence electrons for representative elements is the same as the Roman numeral periodic-table group number 3. the max number of valence electrons for any element is eight (even tho some shells are capable of holding more than 8 electrons, they do so only when they are no longer the outermost shell/not the valence shell)
3 rules to remember when writing chemical formulas for ionic compounds
1. the symbol for the positive ions in always written first 2. the charges on the ions that are present are not shown in the formula; ionic charges must be known to determine the formula, however, the charges are not explicitly shown in the formula 3. the numbers in the formula (the subscripts) give the combining ratio for the ions
two conventions for writing chemical formulas w/ polyatomic ions
1. when more than one polyatomic ion is required in a chem formula, it is enclosed in parentheses, and a subscript placed outside parantheses indicates # -ex: Fe(OH-)_3 2. so the identity of polyatomic ions is preserved, the same elemental symbol may be used more than once in the formula ex: NH_4NO_3 (chem symbol N appears for (NH_4)+ and (NO_3)- ions)
Na+2
10 electrons 12 protons
Cl-
18 electrons 17 protons
magnesium (group IIA) and fluorine (groupVIIA) would, respectively, be expected to form ions with charges of
2+ and 1-
an atom with a 1s2, 2s2, 2p4 electron configuration would most likely form a
2- ion (has 6 electrons in 2nd shell [2 in s subshell and 4 in p subshell] so needs to gain 2 more electrons)
what is the chemical formula for the ionic compound formed when Ca^2+ ions and F- ions combine?
Ca_2F
what is the chemical formula for the compound copper (II) nitrate?
Cu(NO_3)_2 -bc nitrate has a charge of 1- and there's two nitrate ions so the charge of one copper ion has to be 2+
the ion O^2- is isoelectronic with a
Ne atom
what is the chemical formula for the compound tin (II) oxide
SnO
the correct chemical formula for an ionic compound that contains Z^2- ions and X^2+ ions is...
XZ
what is the correct symbol for an atom of X that has gained 3 electrons?
X^3-
if an atom gains one or more electrons, it becomes...
a negatively charged (electrons outnumber protons)
if an atom loses one or more electrons, it becomes...
a positively charged ion (protons outnumber electrons) ***positive charge = LOSS of electrons, NOT gain of protons bc that would change the element***
which of the following is a binary ionic compound a. SO_3 b. CO_2 c. C_2H_3 d. no correct response
d
which of the following is a variable charged metal? a. Zn b. Ag c. K d. no correct response
d
ion arrangement
each ion is surrounded by the nearest neighbors of the opposite charge (in order to maximize attractions between ions and minimize repulsions) ex: in ionic compound sodium chloride (NaCl), no given ion has a single partner; a given sodium ion has 6 immediate chloride ion neighbors; a given chloride ion in turn has 6 immediate sodium ion neighbors **chemical formulas represent RATIO, not structure
the chemical properties of a particle (atom or ion) depend on the particle's...
electron arrangement -so ions and atoms of the same element have completely diff chemical properties -ex: lithium ions used to treat depression, but the element lithium is poisonous
two ions that are isoelectronic would have the same
electron configuration
