CHEM-121_Written Assignment 2 - Thomas Edison State College...

Thomas Edison State College
General Chemistry I with Labs (CHE-121)
Section no.: OL009
Semester and year: FEB2015
Written Assignment 2: Atomic Structure and Chemical Compounds
Answer all assigned questions and problems, and show all work.
1 What is the mass number of an iron atom that has 28 neutrons? (3 points)
(Reference: Chang 2.13)
Z = 26  A = 26 + 28 = 54
2 Calculate the number of neutrons of 239 Pu. (3 points)
(Reference: Chang 2.14)
A = 239, Z = 94
Number of neutrons = 239 – 94 = 145
3 Write the appropriate symbol for each of the following isotopes: (a) Z = 11, A = 23; (b) Z =
28, A = 64 (6 points)
(Reference: Chang 2.17)
a
23
b)
64
11
Na
28
Ni
4 Define, with two examples, the following terms: (a) alkali metals, (b) alkaline earth metal,
(c) halogens, and (d) noble gases . (8 points)
(Reference: Chang 2.22)
a Alkali metals (1A): Lithium (Li); Sodium (Na)
b Alkaline earth metal (2A): Magnesium (Mg); Calcium (Ca)
c Halogen (7A): Fluorine (F); Chlorine (Cl)
d Noble gases (8A): Helium (He); Neon (Ne)
5 Identify the following as elements or compounds: (a) NH
3
, (b) N
2
, (c) CO, (d) Co, and (e)
He. (5 points)
Elements: N
2
, Co, He.