Significant Digits & Scientific Notation

SIGNIFICANT DIGITS & SCIENTIFIC NOTATION

Agenda

1. The Importance of Accuracy and Reliability

2. Significant Digits3. Scientific Notation4. Activity Time!

What If?? Team Competition

Learning Goals

You will be able to successfully answer questions: With the appropriate number of significant

digits In scientific notation

Measurement Tools

Validity & Accuracy

Validity= How “true” something is Reliability= How “consistent” something

is

http://ccnmtl.columbia.edu/projects/qmss/images/target.gif

Rules for Significant Digits

1. All digits that are not zero are significant.

Example: 16.2

Example: 18,648

Rules for Significant Digits

2. Zeros between non zero digits are significant.

Example: 200.5

Example: 100.01

Rules for Significant Digits

3. “Placeholder Zeros” are not significant digits

i.e. Zeros with no numbers to the left

Example: 0.02

Example 0.00009

Rules for Significant Digits

4. Zeros to the right of a decimal point are significant if there is a number to the left of it.

Example: 16.0

Example: 102.100

When Will I Use This?

When answering problems! When adding or subtracting

report the answer with the same number of decimals as the least precise measurement

When multiplying or dividing report answer with the same number of significant digits as the least precise measurement

This may require you to convert your answer to Scientific Notation Only required for numbers

greater than 10

Scientific Notation

1. Reduce the number to a number below 10 With the appropriate number of significant

digits

2. Add to on 10X to make number equivalent to your original answer

Moving the decimal 1 place to the left = 101

Moving the decimal 1 place to the right = 10-1

Scientific Notation

Answer the following with three significant digits

Example: 287

Example: 840,000

Example: 0.0000683

ISOTOPES

Text 1.3: Page 27-31

Learning Goals

By the end of this class, the students will be able to: Differentiate between isotopes of the

same element Determine the relative atomic mass

based on isotope mass or isotopic abundance

Please Remember!

To complete your Grade 10 Review for FRIDAY! Will be Formatively Assessed!

Dinosaur Bones!

Isotopes

Isotopes are like different “species” of an element They only differ in the number of neutrons

in their nucleus

The Atom : Pg 11

Bohr-Rutherford Model

Electron (-)

Proton (+)

Neutron (o)

The Periodic Table: Pg 13

Chemical Nature of the Atom The chemical characteristics

or nature of an element is dependent on the ratio between: Protons (+) and electrons (-)! This balance results in the

charge of the atom The number of neutrons in an

atom can change This does not alter the chemical

nature or characteristics of the atom

Hydrogen Isotopes

How do you Figure?

Mass Number (A) Sum number of

protons and neutrons

Measured in Atomic mass units (u) Equivalent to 1/12th

of a C-12 atom or… I u =/ 1.66x10^24g

How do you Figure?

Atomic Number (Z) Number of

protons in the atom

So how can we determine the number of neutrons??

Determining Number of Protons If Atomic Number (A) is the number of…

Protons and Neutrons And Mass Number (Z) is the number of…

Protons

Neutrons = A- Z

Neutrons = A- Z

But wait…

Didn’t we say you can have MORE than 1 number of neutrons in one element? Wouldn’t that change the weight?

This is why the periodic table also reports the average atomic mass This number takes into

consideration the relative abundance of each individual isotope