CHEMISTRYOCTOBER 30, 2014

LAB 05 - ISOTOPES

LAB STARTER

• You have 2 minutes. You are seated and quiet•Read the Pre-Lab and

answer the question

AIM

•How does the average atomic mass provide us details about the properties of the element?

ISOTOPES

• Atoms of the same atomic number but different masses– Due to different numbers of neutrons

ATOMIC MASS

• Also known as the average atomic mass• Also known as the weighted average atomic

mass– Take into account both the mass and the relative

abundance

EXAMPLE

• CANDY STORE(CANDIUM)– 3 TYPES OF CANDIES (ISOTOPES)• M&M• Skittles• Reese’s

RELATIVE ABUNDANCE• For each types of candies (isotope), need to

know–Count: how many of each types of candies

(Isotope)– Total Count: total number of candies

(isotope) in the candy store–Relative abundance: Percent each type of

candies (isotope) represents of the total. For example, M&M group represent how much of the total group of candies

AVERAGE MASS

• Weigh each type of candies (isotope)• Average Mass per candy (isotope)– Take the mass for each type of candies(isotope)

and divide by the number of candies in each type.• Ex: instead of weighing each M&M, you weigh the

entire group of M&Ms and then you divide the entire mass of the M&Ms by the number of M&Ms to find out how much each M&M approximately weigh (average mass of each M&M)

RELATIVE MASS

• TAKE THE RELATIVE ABUNDANCE BY THE AVERAGE MASS OF EACH ISOTOPE TO GET THE RELATIVE ABUNDANCE– So take the average mass for each type and

multiply by the relative abundance for each type• EXAMPLE: for each type of candies, find out how much

of the entire mass does each type of animals represent – So M&Ms represent how much of the entire candy mass

WEIGHTED AVERAGE MASS

• ADD THE RELATIVE MASS OF EACH TYPE OF ISOTOPES TO GET THE ATOMIC MASS– Add the relative mass of M&M + Skittles + Reese’s

POST LAB QUESTIONS 1-2

• TAKE 1 MINUTE TO ANSWER QUESTIONS 1 AND 2. YOU MAY CONSULT WITH YOUR PARTNER BUT YOUR ANSWER IS YOUR OWN

POST LAB QUESTION 3

• TURN TO THE NEXT GROUP AND OBTAIN THEIR AVERAGE ATOMIC MASS (ANSWER TO #6 ON PAGE 3).

• Write it down and then respond to question 3.• You have 3 minutes to do question 3• You may consult with your partner but the

writing is your own.

POST LAB QUESTION 4

• LET’S REVISIT THE AIM:– How does knowing the atomic mass provide us

with details about the properties of an element? – Take 3 minutes to respond to the question