Transcript Atoms/Molecules/Ions

Welcome to Chem 1A
with Terri Bentzinger
Chapter 1 & 2
E-mail: benzene4president@gmail
Website: http://clas.sa.ucsb.edu/staff/terri/
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Practice Problems
Atoms – Molecules - Ions – Ch. 1
1. For each of the following state if it’s a scientific law, theory or
neither:
a. As a gas expands under constant pressure the gas will cool.
b. The forces between the gas particles are negligible
c. On average heavier gas particles will move slower than
lighter gas particles
d. Gases have a greater average kinetic energy at higher
temperatures because the average velocity increases
with temperature
Atoms – Molecules – Ions – Ch. 1
2. The following data was collected. If it is known that experiment 1
has the formula XY what is the formula of experiment 2.
Experiment
Mass of X
Mass of Y
1
2.55 g
12.75 g
2
1.70 g
4.25 g
Atoms – Molecules – Ions – Ch. 1
3. Two elements R and Q, combine to form two binary compounds. In
the first compound, 14.0 g of R combines with 3.00 g of Q. In the
second compound, 7.00 g of R combines with 4.5 g of Q. Show that
these data are in accord with the law of multiple proportions. If the
formula of the second compound is RQ, what is the formula of the
first?
Atoms – Molecules - Ions – Ch. 2
4. What does the following tell you about an atom:
a. Atomic number
b. Mass number
c. Charge
Atoms – Molecules - Ions – Ch. 2
Atomic Number (Z) ⇒ # of protons
10
Ne
Element Symbol
20.180
Average atomic mass in amu or g/mol
Mass Number (A) ⇒ sum of protons and neutrons
**Note that mass number is NOT on the periodic table**
Atoms – Molecules - Ions – Ch. 2
5. Which of the following represents a pair of isotopes?
a. 32S and 32S2b. O2 and O3
c. 157N and 158O
d. 126C and 136C
e. 188O and 199F
Atoms – Molecules - Ions – Ch. 2
Isotopes ⇒
atoms of the same element (same number of protons) with varying number of
neutrons (different mass number)
ex: Chlorine has two naturally occurring isotopes
35𝐶𝑙 and 37𝐶𝑙
17
17
Mass Number
A
Atomic Number
Z
These can also be written Cl-35 and Cl-37
Atoms – Molecules - Ions – Ch. 2
6. Fill in the following table:
Isotope Symbol
47Ti
90Sr2+
37Cl–
Protons
Neutrons
Electrons
Charge
Atoms – Molecules - Ions – Ch. 2
7. What are ions? How are ions generated?
Atoms – Molecules - Ions – Ch. 2
8. Metals tend to gain or lose electrons?
What charge do group 1 metals form?
What charge do group 2 metals form?
What charge do group 3 metals form?
Atoms – Molecules - Ions – Ch. 2
Non-metals
Metals
Metalloids
Atoms – Molecules - Ions – Ch. 2
9. Non-metals tend to gain or lose electrons?
What charge do group 8 non-metals form?
What charge do group 7 non-metals form?
What charge do group 6 non-metals form?
What charge do group 5 non-metals form?
Atoms – Molecules – Ions – Ch. 2
10. How could you distinguish between ionic compounds, covalent
compounds and acids?
Atoms – Molecules – Ions – Ch. 2
11. Name the following compounds:
a. LiHCO3
g. HClO
b. Na2SO3
h. HNO3
c. (NH4)3PO4
i. SF6
d. Fe(OH)3
j. CO
e. SnO2
k. P2O5
f. HF
Atoms – Molecules – Ions – Ch. 2
Naming Ionic Compounds
First Name (cation)
Second Name (anion)
1. metals with fixed charges
(Grps 1,2,3,Ag,Zn and Cd)⇒
use the elements name as is
2. metals with varying charges
(all other metals) ⇒ use the
elements name and a
Roman numeral
3. NH4+ ⇒ ammonium
1. monoatomic ⇒ elements
name with the suffix –ide
2. polyatomic ⇒ memorize
names (next slide)
Atoms – Molecules – Ions – Ch. 2
Common Polyatomic Ions
Atoms – Molecules – Ions – Ch. 2
Naming Acids
Acids without oxygen
1. Add prefix hydro to
the anion’s name
2. Change suffix to ic acid
ex: HCN ⇒ hydrocyanic acid
or HF ⇒ hydrofluoric acid
Acids with oxygen fox
Change suffix of anion in the acid
ate ⇒ ic acid
ite ⇒ ous acid
ex: HNO2 ⇒ nitrous acid
vs. HNO3 ⇒ nitric acid
Atoms – Molecules – Ions – Ch. 2
Naming Covalent/Molecular Compounds
1. Add a Greek prefix to the first element’s
name if there’s 2 or more
2. Always add a Greek prefix to the 2nd
element and change the suffix to –ide
ex: NF3 ⇒ nitrogen trifluoride
Atoms – Molecules – Ions – Ch. 2
12. Write the chemical formulas for the following compounds:
a. calcium cyanide
b. aluminum sulfate
c. lead(IV) oxalate
d. hydrosulfuric acid
e. sulfuric acid
f. phosphorous acid
g. sulfur trioxide
h. carbon tetrachloride
Atoms – Molecules – Ions – Ch. 2
13. Here are some common names that you’re expected to know; write
the chemical formula.
a. Water
b. Methane
c. Ammonia
Atoms – Molecules – Ions – Ch. 2
14. An element’s most stable ion forms an ionic compound with
chlorine having the formula XCl2. If the mass number of the
ion is 24 and it has 10 electrons, what is the element and how
many neutrons does it have?
Atoms – Molecules – Ions – Ch. 2
You have completed ch. 2
Ch 1 - Answer Key
1. For each of the following state if it’s a scientific law, theory or
neither:
a. As a gas expands under constant pressure the gas will cool.
Law
b. The forces between the gas particles are negligible
Theory
c. On average heavier gas particles will move slower than
lighter gas particles
Law
d. Gases have a greater average kinetic energy at higher
temperatures because the average velocity increases
with temperature
Theory
Ch 1 - Answer Key
2. The following data was collected. If it is known that experiment 1
has the formula XY what is the formula of experiment 2.
Set up a ratio of X/Y for each experiment – expt 1 => 2.55gX/12.75g Y
= 0.2 where as expt 2 => 1.7 g X/4.25 gY = 0.4 Since expt 2 has a
ratio that is twice as much of X then the formula is X2Y
Ch 1 - Answer Key
3. (Ch 2 – problem 77) Two elements R and Q, combine to form two
binary compounds. In the first compound, 14.0 g of R
combines with 3.00 g of Q. In the second compound, 7.00 g of
R combines with 4.5 g of Q. Show that these data are in accord
with the law of multiple proportions. If the formula of the
second compound is RQ, what is the formula of the first?
Set up a ratio of R/Q for each experiment – for expt 1 => 14gR/3gQ =
4.67 and for expt 2 => 7gR/4.5gQ = 1.55 since experiment 1 has 3
times more R the formula is R3Q
Ch 2 - Answer Key
4. a. Atomic number => # protons in an atom
b. Mass number => # protons and # neutrons
c. Charge => # protons – # electrons
5. d. Isotopes are atoms of the same element so they have the same
number of protons however they differ by the number of neutrons
or mass number
6.
Isotope Symbol
Protons
Neutrons
Electrons
Charge
47Ti
22
25
22
none
90Sr2+
38
52
36
2+
37Cl–
17
20
18
1–
Ch 2 - Answer Key
7. What are ions? How are ions generated? Ions are charged atoms
(monoatomic) or charged groups of atoms (polyatomic) – ions are
generated due the gain or loss of electrons producing anions
(negative) and cations (positive)
8. Metals tend to gain or lose electrons?
What charge do group 1 metals form? 1+
What charge do group 2 metals form? 2+
What charge do group 3 metals form? 3+
Ch 2 - Answer Key
9. Non-metals tend to gain or lose electrons?
What charge do group 5 non-metals form?
What charge do group 6 non-metals form?
What charge do group 7 non-metals form?
What charge do group 8 non-metals form?
321No ions
Ch 2 - Answer Key
10. How could you distinguish between ionic compounds, covalent
compounds and acids?
Ionic compounds => cation (typically metal or NH4) and anion (typically
nonmetal)
Covalent compounds => only nonmetals
Acids => covalent compounds that begin with hydrogen (exception =>
although water is technically an acid it will never be named as such)
Ch 2 - Answer Key
11. Name and label the type of compound for each of the following:
a. LiHCO3 – lithium bicarbonate or hydrogen carbonate – ionic
b. Na2SO3 – sodium sulfite – ionic
c. (NH4)3PO4 – ammonium phosphate – ionic
d. Fe(OH)3 – iron(III) hydroxide – ionic
e. SnO2 – tin(IV) oxide – ionic
f. HI – hydroiodic acid – acid
g. HClO – hypochlorous acid – acid/molecular
h. HNO3 – nitric acid – acid/molecular
i. SF6 – sulfur hexafluoride – molecular
j. CO – carbon monoxide – molecular
k. P2O5 – diphosphorus pentoxide – molecular
Ch 2 - Answer Key
12. Write the chemical formulas for the following compounds:
a. calcium cyanide – Ca(CN)2
b. aluminum sulfate – Al2(SO4)3
c. lead(IV) oxalate – Pb(C2O4)2
d. hydrosulfuric acid – H2S
e. sulfuric acid – H2SO4
f. phosphorous acid – H3PO3
g. sulfur trioxide – SO3
h. carbon tetrachloride – CCl4
Ch 2 - Answer Key
13. Here are some common names that you’re expected to know; write
the chemical formula.
a. Water – H2O
b. Methane – CH4
c. Ammonia – NH3
14. An element’s most stable ion forms an ionic compound with
chlorine having the formula XCl2. If the mass number of the
ion is 24 and it has 10 electrons, what is the element and how
many neutrons does it have? Since Cl has a charge of 1- that
tells you that X has a charge of 2+ and if X has 10 electrons
there must be 12 protons therefore X is Mg – if the mass
number is 24 and there’s 12 protons then there are 12 neutrons