Atoms: The Building Blocks of MatterUnit 2

Introduction to the Atom Modern Atomic Theory Subatomic Particles Isotopes Ions

Essential Standards and objectives:1.1.1 Analyze the structure of atoms, isotopes, and ions.1.1.2 Analyze an atom in terms of the location of electrons.1.1.3Explain the emission of electromagnetic radiation in spectral form in terms

of the Bohr model.1.1.4 Explain the process of radioactive decay using nuclear equations and half-life. 2.2.5 Analyze quantitatively the composition of a substance. (Introduction to moles)

The Atom: Smallest particle of an element that retains the chemical properties of the element.

Essential Questions: What is an atom? What is its structure? What determines properties of an element?

Atoms act in orderly, predictable ways.

PHET Build an Atom Use this in the search window Share a computer with a partner Individual work (write your answers on a

separate paper) http://phet.colorado.edu/en/simulation/build-

an-atom

Explain:

How does this graphic demonstrate the characteristics of an atom?

Make sure that you include each graphic (portions) in your explanation

Reading: Cornell notesEssential questions: What are the characteristics

of an atom? In your notes: address both individual atoms and atoms of an element

Modern Atomic Theory1. All matter:2. Atoms of a given element:

3. Atoms cannot be created nor destroyed in:

4. In chemical reactions, atoms are

Atomic Theory (cont.) 5. To form compounds:

Law of Definite ProportionsLaw of Multiple Proportions

Summary Table: Atomic Structure- Subatomic Particles

Subatomic Location Charge Mass ImportanceParticle AMU

Designation of Atomic Structure Atomic number (Z):

On the Periodic Table:

Mass number (A): On the Periodic Table:

Representing atoms Information from symbols and the Periodic

Table

What does this symbol tell us?

Protons: Neutrons: Electrons:

Designations for the Atomic StructureAtomic number (Z): - On the Symbol - On the Periodic TableMass number (A): - On the Symbol - On the Periodic Table20

Ca

40.08

Review: What is Z? What is A?

Determine the number of protons, neutrons, and electrons.

31

GaGallium

69.72

32

GeGermanium

72.61

Periodic Table: an Important Tool in Chemistry but no set rules for what is included and where

16

S 32.06

S1632.06

How can we tell which is the atomic number and the mass number?

Atomic Mass Unit

AMU

 The “amu” is defined as one twelfth of the mass of an atom of carbon-12  (with 6 protons and 6 neutrons) and has a value of 1.660538921×10−27 kg.

AMU = relative measurement and used for comparison

Organization of the Periodic TableColumns – Groups All the elements have similar chemical and physical

properties All will chemically react in a similar way Names of groups

Rows – Periods Elements have same number of energy levels

Isotopes

Isotopes

Isotopes: Atoms of an element with different masses

Naturally occurring Some are stable and some are radioactive

(unstable) Isotopes of an element have the same number

of ___________ and a different number of ______________.

Identifying Isotopes Isotope Notation1.

2.

On the Periodic Table, the number with the Decimal point is:

Atoms of the Same Element

Atoms of the Same Element

Atoms of the Same Element

Atomic Mass

Weighted Average Mass of isotopes Based on the percentage of each isotope

present.

Grades are often computed using a weighted average. Suppose that homework counts 10%, quizzes 20%,

Labs 10% and tests 60%. If: homework grade is 92quiz grade is 68lab grade is 88 test grade is 81What’s the overall grade?

Practice Atomic Structure

Identify the number of proton, neutron, & electrons of an atom of a specific element

Rounding the atomic mass on the Periodic Table gives the mass of the most common isotope

Atomic Number & Isotopes Correct symbol: A & Z Complete the table Complete the questions.

Practice: Find the Average Atomic Mass

Nucleus of each atom is represented Graphic below #4 - explains #5-7

Isotopes: Atomic Number & Mass Number Determine based on the chart – not the PT 2 Isotope notations

Element – A (X-A) A

ZX

Find Average Atomic Mass

Atomic Number & Isotope

Isotopes: Atomic Number & Mass Number

Element Isotope Symbol

Atomic Number Z

Mass Number A

# of protons

# of neutrons

# of electrons

What is the atomic mass of Nitrogen given: N-14 is 99.64% of all nitrogen N-15 is 0.36% of all nitrogen

What is the atomic mass of Indium if:

In-113 is 4.24% In-115 is 95.72%

Calculate % Abundances from Masses Requires the use of 2 equations and 2

unknowns. Isotope 1(X) + Isotope 2(Y) = Atomic Mass X + Y = 1 Substitute and solve for X or Y!

What are the percent abundances of Vanadium if V-50 + V-51 = 50.94 amu

What are the percent abundances for Gallium if: Ga-69 + Ga-71 = 69.72

Atom: Scanning Tunneling Microscope

Study of atomic particles

Scanning Tunneling Microscrope

Development of the Atomic Theory Essential Question: Why do elements have

different properties?

Development of the Modern Atomic Model

Here are several models of the atom as they were developed in history:

............ ......

................

Ancient Question

Atomic investigation

Bohr

Quantum Model Electron Cloud model of

the atom

Representing atoms with the Bohr model

Representing atoms with the Bohr Model

Bohr Model – Simplified but Useful ModelGroup

1Group

2Groups

2-12Group

13Group

14Group

15Group

16Group

17Group

18

P1

P2

P3

Bohr Model & the Periodic Table Making Conclusions

Compare and Contrast Why are elements placed in a group (column)? Why are elements placed in a period (row?)

Changing An Atom

Changing an Atom

Ions Atoms can lose or gain electrons when bonding to

make ionic compounds We keep track of the number of electrons that can be

lost or gained with oxidation numbers (also known as charges)

Ions are charged particles –when an atom has too many or too few electrons to be neutral No change to the nucleus Proton and neutrons stay the same number.

Ions – Charged Particles7. When atoms of elements form ions

(__________ __________, they must either __________ or _______ valence electrons.

Gain/lose? Charge Ion type? Metals

Non-metals

Why are ions important? The ___________________ charged particles

are like a magnet.

Therefore, they are strongly held together in an ______________ _____________ forming an _____ ________________.

Representing atoms with the Bohr Model

IonsLithium atom - Lithium ion Ion Symbolp+ p+nº nºe- e-Fluorine atom Fluorine ion p+ p+nº nºe- e-

Ions and ChargeNet electric charge

Note change

8

Ions and Charges for Representative Elements (Oxidation number keep track of electrons)

Ion Making

Making an ion of analkali metal, First column in the periodic chart,Leaves all the ions with a plus one chargeAnd they’re all a whole lot smallerthan they were before.

Second column over,Alkaline earths,Loses 2 electrons easily,So their ions all have a plus 2 charge, And they’re smaller than their neighbors to the left.

Next door, aluminum,the 3rd step overhas 3 electronsIt’d like to have removed.When they are gone, it has a +3 charge,And, by gosh!, It’s evensmaller than the “lefter” two.

But add one electron To the halogen group,So they all have a Negative one charge.They get 8x bigger thanThey were before.Puffed up, very large.

Sulfur and oxygenneed 2 electrons to give each a full andcomplete electron shell.Thus, minus 2 is their ionic charge.And they’re a little largerThan the “Hal-ions”.

Add three electrons to the nitrogen group.So that group has a triple minus charge.And the pattern we see makes it very clear.Negative ions are large!

Mole Resources for students http://molechemistry.info/

Nuclear Chemistry

Neutron to Proton Ratio

Types of Radiation

Alpha Decay

Beta decay

Gamma Decay

Radiation Strength

Nuclear Equations1. 1

1H + 94Be ---> 6

3Li + ? 2. 27

13Al + 42He ---> 30

15P + ?3. 24

12Mg 2412Mg + ?

4. 23892U 234

90Th + ?

5. 146C 0

-1e + ?6. 239

94Pu + 42He 242

96Cm + ?Nuclear Equations Practice Website

Half-life Measure of Radioactive decay rate. Measured as the time it takes for ½ of a

sample of radioisotope’s nuclei to decay into its products.

Half LifeDecay of a radioisotopeNumber of Half-Lives

Elapsed time Amount remaining

0 0 100 g

1 1.5 year 50 g

2 3 years 25 g

3 4.5 years 12.5 g

Half Life Problems How much of a 100g sample of an unstable

isotope remains after 25 years if the half life is 5 years?

3.1 g

Half Life Problems How much of a 60g sample of an unstable

isotope remains after 2 days if the half life is 12 hours?

7.5 g

Half Life Problems How much of a 20 g sample of an unstable

isotope remains after 6 sec if the half life is 0.5?

0.005 g

Atomic Nucleus (also known as nuclide)

Mass

Energy

Volume

Radioactive IsotopesA radioactive isotope has an unstable nucleus

that undergoes spontaneous changes. - Emits particles and energy

- Transmutates into another element

Particles emitted from a radioactive isotope

Type Symbol Charge Mass

Nuclear reactionsTotal number of atomic numbers and the total

mass numbers must be equal on both sides of the equation.

Examples:

Radioactive decay

No 2 radioactive isotopes decay at the same rate. Therefore, decay rate can be used to identify the isotope. Decay is measured by half life.

Fission and Fusion

Origins of Element

Got Calcium Where are most elements created? When was H and He created? What elements are made by small stars? What additional elements are made by large

stars? What elements are made by supernovae (large

exploding stars)?

Teachers' Domain: The Origin of the Elements

Teachers' Domain: The Elements: Forged in Stars