Name ______________________

You should be able to complete this worksheet after studying Sections 4.1 – 4.3 in your textbook. This will let you see if you understand the terms we use to describe the structure of an atom.

1) What are the three major subatomic particles’ masses (amu’s and grams), charge (elementary charges), and location (general vicinity)?

Name of Particle	Charge on particle (el ch)	Location
Proton	+1	In the nucleus.
Neutron	0	In the nucleus
Electron	-1	Outside the nucleus.

2) Fill in the cells.

Symbol	Atomic Number (Z)	Mass Number (A)	# of Protons	# of Neutrons	# of Electrons	Atomic Mass (amu)
1) 3^7Li	3	7	3	4	3	6.941
2) 1^1H	1	1	1	0	1	1.00794
3) 19^39K^1+	19	39	19	20	18	39.0983
4) ^15O^2-	8	15	8	7	10	15.9994
5) 13^27Al ^3+	13	27	13	14	10	26.981538
6) 30^65 Zn ^2+	30	65	30	35	28	65.39
7) 2^4 He	2	4	2	2	2	4.002602
8) 17^35 Cl ^1-	17	35	17	18	18	35.453
9) 14^28 Si ^4+	14	28	14	14	10	28.0855
10) 92^238U	92	238	92	146	92	238.02891

Is #1 the most common isotope of Li? _yes Is #4 the most common isotope of O? no Briefly explain your reasoning.

I am assuming there is one dominant isotope that is responsible for most of the abundance of the element. If this is true, then rounding off the Atomic Mass to the nearest whole number will give the mass number of the most abundant isotope. Li rounds to 7, O rounds to 16.

3) Use the data in the table below to find the atomic mass of each element. Compare your calculation to the atomic mass listed on your periodic table.

* Natural Percent Abundance of Some Elements

Name	Symbol	Natural Percent Abundance	Mass (AMU)	Calculated Average Atomic Mass	Accepted Average Atomic Mass
Hydrogen	^1H ^2H ^3H	99.985 .015 negligible	1.0078 2.0141 3.0160	1.0079	1.00794
Oxygen	^16O ^17O ^18O	99.759 .037 .204	15.995 16.995 17.999	15.995	15.9994
Chlorine	^35Cl ^37Cl	75.77 24.23	34.969 36.966	35.453	35.453

* Source: Prentice Hall Chemistry (P. 114)

Show your work in the space provided below.

Hydrogen

Average Atomic Mass

(.99985 x 1.0078) + ( .00015 x 2.0141) = 1.0079

Oxygen

Average Atomic Mass

(.99759 x 15.995) + ( .00037 x (16.995) + (.00204 x 17.999) = 15.995

Chlorine

Average Atomic Mass

(.7577 x 34.969) + ( .2423 x 36.966) = 35.453