Welcome to Chem 1Awith Terri Bentzinger

Chapter 1 & 2E-mail: benzene4president@gmail

Website: http://clas.sa.ucsb.edu/staff/terri/

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AdditionalPractice Problems

Atoms – Molecules - Ions – Ch. 11. 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. 12. 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. 13. 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. 24. What does the following tell you about an atom:

a. Atomic number

b. Mass number

c. Charge

Atoms – Molecules - Ions – Ch. 2

10

Ne20.180

Atomic Number (Z) ⇒ # of protons

Element Symbol

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. 25. Which of the following represents a pair of isotopes?

a. 32S and 32S2-

b. O2 and O3

c. 157N and 15

8O

d. 126C and 13

6C

e. 188O and 19

9F

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

and

These can also be written Cl-35 and Cl-37

Mass NumberA

Atomic NumberZ

Atoms – Molecules - Ions – Ch. 26. Fill in the following table:

Isotope Symbol Protons Neutrons Electrons Charge

47Ti

90Sr2+

37Cl–

Atoms – Molecules - Ions – Ch. 27. What are ions? How are ions generated?

Atoms – Molecules - Ions – Ch. 28. 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

Metalloids

Metals

Atoms – Molecules - Ions – Ch. 29. 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. 210. How could you distinguish between ionic compounds, covalent

compounds and acids?

Atoms – Molecules – Ions – Ch. 211. 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 is2. metals with varying charges (all other metals) ⇒ use the elements name and a Roman numeral3. 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 AcidsAcids without oxygen Acids with oxygen fox

1. Add prefix hydro to the anion’s name

2. Change suffix to ic acidex: HCN ⇒ hydrocyanic acidor HF ⇒ hydrofluoric acid

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 Compounds1. Add a Greek prefix to the first element’s

name if there’s 2 or more2. Always add a Greek prefix to the 2nd

element and change the suffix to –ideex: NF3 ⇒ nitrogen trifluoride

Atoms – Molecules – Ions – Ch. 212. 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. 213. 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. 214. 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 Key1. 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 Key2. 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 Key3. (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 Key4. 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 Key7. 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 Key9. Non-metals tend to gain or lose electrons?

What charge do group 5 non-metals form? 3-

What charge do group 6 non-metals form? 2-

What charge do group 7 non-metals form? 1-

What charge do group 8 non-metals form? No ions

Ch 2 - Answer Key10. 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 Key11. 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 Key12. 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 Key13. 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