Chemistry 121
Worksheet 1 Notes
Oregon State University
Dr. Richard L Nafshun
Welcome to Chemistry 121 Recitation
Instructions:
Solve the worksheet problems using any resources available—resources include your text, notes, each other, and to a
limited degree your Teaching Assistant. If you find useful information in the text or notes, consider entering it on
one side of your 3" x 5" notecard for Exam 1.
While this work will not be collected, clearly show your work on your own notebook paper. This will enable you to
communicate your thinking to others and generate a study aid. Clearly showing your work will also assist in
organization.
Work through as many problems as time allows. You are encouraged to finish problems before the next recitation
meeting. You are encouraged to meet with your classmates outside of scheduled class time.
1.
Sketch a cartoon of the PTE (Periodic Table of the Elements). Identify the metal
and non-metal regions with labels and a "staircase."
2.
List six metals by name and symbol.
lithium
copper
lead
silver
aluminum
magnesium
Li (Group 1)
Cu (Transition metal)
Pb (Transition metal)
Ag (Transition metal)
Al (Group 3 or 13)
Mg (Group 2)
and many others. These are located to the left of the staircase.
Additional notes:
The Group 1 metals are +1 when combined with non-metals to form ionic compounds.
The Group 2 metals are +2 when combined with non-metals to form ionic compounds.
Aluminum is a metal and is +3 when combined with non-metals to form ionic
compounds.
3.
List six non-metals by name and symbol.
oxygen
carbon
nitrogen
neon
sulfur
fluorine
O (Group 16)
C (Group 14)
N (Group 15)
Ne (Group 18)
S (Group 16)
F (Group 17)
and many others. These are located to the right of the staircase.
Additional notes:
The Group 18 non-metals are inert. They do not typically form compounds.
The Group 17 non-metals are -1 when combined with metals to form ionic compounds.
The Group 16 non-metals are -2 when combined with metals to form ionic compounds.
The Group 15 non-metals are -3 when combined with metals to form ionic compounds.
The Group 14 non-metals are -4 when combined with metals to form ionic compounds.
4.
NaCl is known as "table salt" or sodium chloride.
What group number is sodium in? Group 1.
What group number is chloride in? Group 17
Is NaF expected to exist? Explain. Yes. Na is +1 and F is –1 in when forming ionic
compounds. So NaF is electronically neutral (the charges cancel other out).
Is LiF expected to exist? Explain. Yes. Li (Group 1) is +1 and F (Group 17—one
group from the inert gases) is –1 when forming ionic compounds. So LiF is
electronically neutral (the charges cancel other out).
Is MgF expected to exist? Explain. No. Mg (Group 2) is +2 and F (Group 17—one
group from the inert gases) is –1 when forming ionic compounds. So MgF is not
electronically neutral (the charges DO NOT cancel other out). Magnesium fluoride has
the chemical formula MgF2.
Can you explain why one Mg2+ and two F- are the correct chemical combination?
5.
CaCl2, calcium chloride, has many applications (http://www.dow.com/calcium/)
including water treatment. What group number is calcium in? Group 2.
What group number is chloride chlorine in? Group 17.
Is CaF2 expected to exist? Explain. Yes, the ionic compound proposed in electrically
neutral.
Is LiCl2 expected to exist? Explain. No. The proposed chemical formula is not
electrically neutral.
Is MgF2 expected to exist? Explain. Yes. MgF2 is electrically neutral.
6.
Lithium oxide, Li2O, readily absorbs carbon dioxide and water vapor from the air.
What group number is lithium in? 1.
What group number is oxygen in? 16.
Is Li2F expected to exist? Explain. No, LiF is electrically neutral.
Is Na2S expected to exist? Explain. Yes, it is electrically neutral.
Is Cs2Se expected to exist? Explain. Yes, it is electrically neutral.
7.
Magnesium selenide, MgSe, is a light brown powder that is unstable in air. What
group number is magnesium in? 2.
What group number is selenium in? 16.
Is MgO expected to exist? Explain. Yes, it is electrically neutral.
Is CaS expected to exist? Explain. Yes, it is electrically neutral.
Is BaCl expected to exist? Explain. No, it is not electrically neutral. BaCl2 is
electrically neutral.
8.
What is the chemical formula of sodium oxide? Na2O.
9.
Does neon form chemical compounds? Explain. No, neon is in Group 18 (it is an inert
gas). True, neon has been made to form compounds, but these are extreme cases and
have earned Noble prizes for some folks.
10.
Which of the following formulas are correct or incorrect? Explain why.
(Incorrect formulae have correct formula listed to the right)
(A)
(D)
(G)
(J)
(M)
LiCl2 (LiCl)
Na2O
FrF
Li2S
K2S
(B)
(E)
(H)
(K)
(N)
MgCl2
Mg2O (MgO)
SrI2
CaO
BaCl (BaCl2)
(C)
(F)
(I)
(L)
(O)
AlCl2 (AlCl3)
Al2O3
BeF2
KS
(K2S)
KNe (Ne does not
normally form
compounds)