JLH Chem chapter 3 Flashcards
Individual atoms are rarely encountered in nature. Instead, atoms are far more commonly joined together to form compounds. What are the two types of chemical compounds?
Ionic compounds
Covalent compounds
Ionic compound
compounds composed of positively & negatively charged ions held together by strong electrostatic forces.
usually formed when a metal reacts with a nonmetal or polyatomic ion
NaCl (table salt)
What are electrostatic forces?
electrical attraction between oppositely charged ions.
Covalent compounds
compounds that composed of individual molecules, discrete groups of atoms that share electrons (share equally)
What are some examples of covalent compounds?
H2O
CH4 (Methane)
Methane is the main component of natural gas
what does Bonding mean?
joining of two atoms in a stable arrangement
What happens in bonding?
elements gain, lose, or share electrons to attain the electronic configuration of the noble gas closest to them in the periodic table.
Bonding involves only what of an atom?
the valence electrons
Ionic bond
result from the transfer of electrons from one element to another
Covalent bonds
result from the sharing of electrons between two atoms
Ionic bonds form between what elements on the periodic table?
ionic bonds form between a metal and a nonmetal
(NaCl)
What do covalent bonds form with?
two nonmetals or
metalloid and a nonmetal
molecule
compound or element containing two or more atoms joined by a covalent bond
When a metal and nonmetal combine, what is the bond?
(Na + I)
ionic bond
NaI
when two nonmetals combine, or a metalloid bonds with a nonmetal, what is the bond?
(H2 + O2)
covalent bond
(H2O2 hydrogen peroxide)
Is CO ionic or covalent
covalent
(both elements are nonmetals)
Is CaF2 ionic or covalent?
Ionic
Is this molecule an ionic bond or covalent bond?
Is it a compound or element?
- covalent bond
- compound
Is this molecule a compound or element?
(N2)
Element
remember, compounds are 2 different elements
Ionic compounds consist of oppositely charged ____ that have a strong _____________ __________
Ionic compounds consist of oppositely charged ions that have a strong electrostatic attraction
What are the two types of ions?
cations +
anions -
What type of ion has fewer electrons than protons?
cation
What type of ion has more electrons than protons?
anion
The nature and magnitude of the charge on an ion depend on what?
The position of an element in the periodic table.
In forming an ion, an atom of a main group element loses or gains electrons to obtain the electronic configuration of the noble gas closest to it in the periodic table
Sodium (group 1A) has an atomic number of 11, giving it 11 p & 11 e- in the neutral atom. This gives sodium one more electron than neon, the noble gas closest to it in the periodic table. What happens with Na to become more stable?
in losing one electron, sodium forms a cation with a +1 charge, which still has 11 protons, but now has only 10 electrons in its electron cloud (2 in first shell and 8 in 2nd shell).
1s22s22p63s1 → 1s22s22p6 (Na+)
Magnesium has two more electrons than neon, the noble gas closest to it in the periodic table. What happens with Mg in order to become more stable?
Mg has 2 valence electrons. Loss of these two valence electrons forms a magnesium cation, symbolized as Mg2+
1s22s22p63s2 → 1s22s22p6
What type of ions do metals form?
cations
Do cations change size from the atom they were when neutral?
Cations are smaller in size than the atoms from which they are formed because a cation has more protons than electrons, the positively charged nucleus pulls the remaining electrons closer.
What happens with chlorine in order to become more stable?
Neutral Cl has 17 electrons (one less electron than argon, the noble gas closest to it).
By gaining one electron, Cl forms an anion with a -1 charge (Cl-)
1s22s22p63s23p5 → 1s22s22p63s23p6
What type of ions are formed from nonmetals?
anions
by gaining one, two, or sometimes three electrons, an atom forms an anion with a completely filled outer shell of electrons.
Are anions larger or smaller than the atoms from which they are formed?
Larger, because an anion has more electrons than protons, the electrons are held less tightly by the positively charged nucleus, and the anion size is larger than the atom size.
how are ions written?
ions are written with the element symbol followed by a superscript to indicate the charge.
Na+, Mg2+, O2-
When is a main group element especially stable?
When it possesses an octet of electrons in its outer shell.
Identify the ion shown in the molecular art and give its ion symbol
Li+
1 more proton than electrons
Give the symbol for the ion shown
N3-
Because the number of protons equals the atomic number (quantity of p identifies the element). If the number of electrons is greater than the number of protons, the charge is negative (anion). If the number of protons is greater than the number of electrons, the charge is positive (cation). Write an ion symbol for an atom with 9 protons and 10 electrons.
F-
How many protons and electrons are present in Ca2+
O2-?
Ca2+ (20 p, 18 e-)
O2- (8p, 10 e-)
Which sphere (A or B) represents S and which represents S2-?
A = S
B = S2-
Which sphere (C or D) represents Li and which represents Li+?
C = Li+
D = Li
elements in the same group form ions of similar charge.
For metals in groups 1A, 2A, and 3A, the group number = what?
charge on the cation
- Group 1A elements have one V electron. Loss of this electron forms a cation with a +1 charge.*
- Group 2A elements have two V electrons. Loss of both electrons forms a cation with a +2 charge.*
All of the cations derived from group 1A-3A elements have an octet of outer shell electrons except for Li+ and Be2+. Li+ and Be2+ have a 1s2 electronic configuration like helium, the noble gas to which they are the closest.
These cations are especially stable because they have a filled outer shell of electrons, although they do not have an octet of electrons.
All of the cations derived from group 1A-3A elements have an octet of outer shell electrons except for Li+ and Be2+. Li+ and Be2+ have a 1s2 electronic configuration like helium, the noble gas to which they are the closest.
nonmetals form anions. For nonmetals in groups 5A, 6A, and 7A, the anion charge = what?
8 - (the group number)
Group 5A elements have five valence electrons. A gain of three electrons forms an anion with a -3 charge (anion charge = 8 - 5).
Use the group number to determine the charge on an ion derived from barium
from sulfur
Ba is in group 2A: Ba2+
S is in group 6A: S2-
The transition metals form cations (not so easy to predict)
Iron forms two different cations Fe2+ & Fe3+.
How are these formed?
Fe2+ is formed by losing two v electrons from 4s.
Fe3+ is formed by losing two from 4s & one from 3d
Why is the octet rule not usually followed with transition metals?
Transition metals generally have additional d electrons that the nearest noble gas does not.
Identify the ion
Co3+
What are major cations in our body?
Mg2+ (higher inside cells)
K+ (higher inside cells)
Ca2+ (higher outside cells)
Na+ (higher outside cells)
What is the major cation present in blood and extracellular body fluids?
Na+
its concentration is carefully regulated through a number of mechanisms to maintain blood volume & blood pressure within acceptable ranges that permit organ function.
Where is Ca2+ mainly found?
in solid body parts such as teeth & bones, but it is also needed for proper nerve conduction and muscle contraction, as is Mg2+.
In addition to the four common cations present throughout the organs of the body, there are two others that are important. What ion is essential for oxygen transport by red blood cells?
Fe2+
In addition to the four common cations present throughout the organs of the body, there are two others that are important. What ion is present in red blood cells, gastric juices, and other body fluids?
Cl-
along with Cl-, Na+ plays a major role in regulating the fluid balance in the body.
Although Na+ is an essential mineral needed in the daily diet, the average American consumes how much compared to the recommended daily allowance (RDA)?
The average American consumes three to five times the recommended RDA (2,400 mg).
What is excess sodium intake linked to?
High BP
Heart disease
What does dietary Na+ come from?
salt (NaCl), added to meals.
Na+ is also added during the preparation of processed foods and canned products.
a 3.5 oz serving of fresh asparagus has 1 mg of Na+. The same serving size of canned asparagus contains how much Na+?
236 mg of Na+
Mn2+ is an essential nutrient needed for blood clotting and the formation of the protein collagen.
a) How many protons and electrons are found in a neutral manganese atom?
b) How many electrons and protons are found in the cation Mn2+
c) Write the electronic configuration of the element manganese and suggest which electrons are lost to form the Mn2+ cation.
a) 25 p, 25 e-
b) 25 p, 23 e-
c) 1s2 2s2 2p6 3s2 3p6 4s2 3d5
The two 4s2 valence electrons would be lost to form Mn2+
When a metal transfers one or more electrons to a nonmetal, what is formed?
ionic bond
Ionic compounds are composed of cations and anions
The ions in an ionic compound are arranged to maximize the attractive force between the oppositely charged species. Give an example using NaCl.
In NaCl, each Na+ cation is surrounded by six Cl- anions, & each Cl- anion is surrounded by six Na+ cations.
In this way, the positively charged cations are located closer to the negatively charged anions and farther from the particles from which they are repelled - cations.
The sum of the charges in an ionic compound must always be equal to what?
Zero
(because a sodium cation has +1 charge and the chloride anion has -1 charge, there must be one Na+ cation for each Cl- anion; thus the formula is NaCl.)
Since Ca is located in group 2A, when it loses its valence electrons it becomes Ca2+. So when Ca2+ forms an ionic compound with F (F is in group 7A becoming F-), there must be two F- anions for each Ca2+ cations to have an overall charge of zero. How do we write the formula for this ionic compound?
We use subscripts
CaF2
(two F per Ca)
What would the formula be for Li and O forming an ionic compound?
Li2O
Two Li+ cations (+2 charge total) combine with one O2- anion (- charge)
What would the formula be when Al and O form an ionic compound?
Al2O3
Two Al3+ cations (+6 charge total) combine with three O2- anions (-6 charge total).
Steps to write a formula for an ionic compound
Identify which element is the cation and which is the anion
Determine how many of each ion type are needed for an overall charge of zero
Place the cation first and then the anion and omit charges
When sterling silver tarnishes, it forms an ionic compound derived from silver and sulfur. Write the formula for this ionic compound.
Ag2S
Draw a representation using molecular art for a solution of the following ionic compound dissolved in water:
Na2S
What ionic compound is an essential nutrient added to table salt?
Potassium iodide (KI)
What ionic compound is added to toothpaste to strengthen tooth enamel and help prevent tooth decay?
Sodium fluoride (NaF)
What is the ionic compound for zinc oxide?
ZnO
Chemical nomenclature
Assigning a name to each compound
Cations of main group metals are given the name of the element from which they are formed. It is common to add the word “___” after then name of the metal cation to distinguish it from the neutral metal itself.
“ion”
For example, when the concentration of sodium in a blood sample is determined, what is really measured is the concentration of sodium ions
There are 2 methods for naming cations. Method 1 and Method 2.
What is method 1?
Follow the name of the cation by a Roman numeral in parentheses to indicate its charge.
Fe2+ = iron(II)
There are 2 methods for naming cations. Method 1 and Method 2.
What is method 2?
Use the suffix -ous for the cation with the lesser charge and the suffix -ic for the cation with the higher charge.
Fe2+ = ferrous
Fe3+ ferric
How are anions named?
by replacing the ending of the element name by the suffix -ide.
Bromine = BR- = Bromide
Chlorine = Cl- = Chloride
Oxygen = O2- = Oxide
What is the name of :
S2-
Sn4+
S2- = sulfide
Sn4+ = tin or Sn(IV)
How do you name ionic compounds with cations from main group elements?
Name the cation and then the anion
Na+ F- -→ NaF
What is the name for Mg2+ with Cl-?
MgCl2
Because for every 1 Mg there are 2 Cl to make the net charge zero
What is the name of the ionic copound Na2S?
sodium sulfide
How do you name an ionic compound that contains a metal with variable charge?
example: CuCl2
Copper(II) chloride
because there are two Cl- anions, each of which has a -1 charge, the copper cation must have a +2 charge to make the overall charge zero
What is the name for the ionic compound SnF2
tin(II) fluoride
since F has a negative 2 charge, Sn must have a +2 charge
Give the name for:
Cu2O
CuO
Cu2O: Copper(II) oxide
CuO: Copper(I) oxide
how do you get the formula from the name if an ionic compound?
- ) Identify the cation & anion
- ) Cation goes first w/roman numeral
- ) Use the charge on the cation to determine # of ions of anion needed to balance charge
Write the formula for tin(IV) oxide.
Tin is the cation with +4
Sn4+
Oxide is the anion (2-)= O2-
two (-2) anions are needed for each +4 cation
SnO2
write the formula for sodium oxide
Na2O
Ionic compounds
Crystalline solids composed of ions packed to maximize the interaction of the positive charge of the cations and negative charge of the anions.
What determines the way ionic compounds are packed in the crystal lattice?
Relative size and charge of the ions.
Ionic solids are held together by extremely strong interactions of the oppositely charged ions. How is this reflected in the melting point and boiling point of an ionic compound?
- ionic compounds have very high melting points.*
- It takes a great deal of energy to separate the ions* from each other.
What is the melting point of the ionic compound NaCl?
Boiling point of liquid NaCl?
Melting point of NaCl: 801 °C
Boiling point of liquid NaCl: 1413 °C
A great deal of energy is needed to overcome the attractive forces present in the liquid phase, too, to form ions that are far apart and very disorganized in the gas phase, so ionic compounds have extremely high boiling points
A good amount of ionic compounds are soluble in water. What happens when an ionic compound dissolves in water?
The ions are separated, and each anion & cation is surrounded by water molecules.
The interaction of the water solvent with the ions provides the energy needed to overcome the strong ion-ion attractions of the crystalline lattice.
aqueous solution
contains a substance dissolved in liquid water
When an ionic compound dissolves in water, the resulting aqueous solution does what?
conducts an electric current
What is one thing that distinguishes ionic compounds from other compounds?
When an ionic compound dissolves in water, the resulting aqueous solution conducts an electric current.
4 physical properties of ionic compounds
- high melting points/high boiling points
- usually dissolve in water
- their solutions conduct electricity
- they form crystalline solids
Sometimes ions are composed of more than one element. Why do these polyatomic ions bear a charge?
the total number of electrons it contains is different from the total number of protons in the nuclei of all of the atoms.
polyatomic ion
cation or anion that contains more than one atom
The atoms in a polyatomic ion are held together by what type of bond?
covalent bonds
- but, because the ions bear a charge, it bonds to other ions by ionic bonding.*
- Calcium sulfate, CaSO4, is composed of a calcium cation, Ca2+, and the polyatomic anion sulfate, SO42-.*
We will encounter only two polyatomic cations. What are they?
H3O+, hydronium ion (plays a role in acid-base chemistry)
NH4+, ammonium ion
Is there many common polyatomic anions?
In contrast to polyatomic cations, there are many polyatomic anions.
most of these contain a nonmetal like carbon, sulfur, or phosphorus, usually bonded to one or more oxygen atoms.
some common polyatomic anions
The names of most polyatomic anions end in what suffix?
-ate
Exceptions to this generalization include hydroxide (OH-) and cyanide (CN-)
When would you use the suffix -ite?
When an anion has one fewer oxygen atoms than a similar anion that already is named with the -ate ending.
When two anions differ in the presence of a hydrogen
(SO42- and HSO4-)
How do you name the anion with hydrogen?
either add the prefix bi-
bisulfate
or
add the word hydrogen
hydrogen sulfate
When the cation and anion both have the same charge (+ = -), how do you write the formula?
use
Na+ & NO2-
and
Ba2+ & SO42-
NaNO2 (sodium nitrite)
BaSO4 (Barium sulfate)
You don’t need to add the charges if they have an overall charge of zero
Write the formula for magnesium (Mg2+) and hydroxide (OH-)
Mg(OH)2
for every one magnesium there needs to be two hydroxides to have an overall charge of zero
What is the formula for calcium and phosphate?
Ca2+ and PO43-
Ca3(PO4)2
Place parenthesis around the anion
Write the formula for the compound formed when the sulfate anion (SO42-) combines with the cation magnesium
MgSO4
Write the formula for the compound formed when the sulfate anion (SO42-) combines with the cation aluminum
Al2(SO4)3
Memorize these bold faced anions
memorize these key features used in naming ionic compounds
name the polyatomic ion NaHCO3
sodium bicarbonate
or
sodium hydrogen carbonate
name the polyatomic ion Al2 (SO4)3
aluminum sulfate
name this compound
Mn (CH3CO2)2
manganese acetate
What is the charge on the cation in GaN?
+3
Ionic compounds are the active ingredients in several over-the-counter drugs. Examples include calcium carbonate (antacid in Tums), magnesium hydroxide (an active component in Maalox & milk of magnesia), and iron(II) sulfate (iron supplement).
What are the chemical formulas for the bolded ionic compounds?
calcium carbonate: CaCO3
magnesium hydroxide: Mg(OH)2
iron(II) sulfate: (FeSO4)
What important polyatomic anion controls the acid-base balance of blood and is given as an intravenous drug?
Bicarbonate (HCO3-)
When the blood becomes too acidic, what is administered intravenously to decrease acidity?
sodium bicarbonate
NaHCO3
What over the counter laxative can be given intravenously to prevent seizures caused by extremely high blood pressure associated with some pregnancies?
Magnesium sulfate
MgSO4
Although much of the body is composed of compounds held together by covalent bonds, about 70% of bone is composed largely of a complex ionic solid with the formula Ca10(PO4)6(OH)2 called what?
hydroxyapatite
