Today is Thursday,September 10th, 2015

• Think about what’s in these extremely attractive cookies:

• Of what are they made?

http://www.hersheys.com/recipes/lib/inc/showImage.asp?id=5368&size=m

In This Lesson:Atomic Structure,

Ions, Isotopes(Lesson 2 of 9)

Today’s Agenda

• Today we begin our study of biology. – Biology is the study of living things.

• Why not begin at the beginning, then?

• Non-living things!– Atoms/Elements– Subatomic Particles– Isotopes/Ions– Bonds

• James Bonds

By the end of this lesson…

• You should be able to describe the three main components of an atom and what happens when each of these components changes in number.

Where is this in my book?

• Academic:– P. 35-37

• Honors:– P. 16 and following…

Cookie Chemistry

• Imagine, for simplicity, this cookie is made of flour, baking soda, lots and lots of sugar, vanilla extract, and chocolate.– Is that as specific as you can get?

• Let’s take just chocolate. What’s the chocolate made of?– As a matter of fact, over 500 separate chemical

compounds.

How low can you go?

• For another, more to the point example, think about the air you’re (hopefully) breathing right now. What’s it made of?– I’ll give you a hint: Typically, it’s got 4 main

parts.

Air

• With each breath you take, you suck this mixture in:– Nitrogen (78%)– Oxygen (20.95%)– Argon (0.93%)– Carbon Dioxide (0.038%)– Others

http://www.uigi.com/air.html

So who gives a...?

• If we broke the air mixture (keyword) down into oxygen, carbon dioxide, nitrogen, and argon, how can we break it down again, into unique parts?

• What am I getting at?

Eventually…

• By getting deeper and deeper into matter (that’s the scientific term for “stuff”), we reach the atom.

• The atom is the smallest unique part of an element.• An element (see below definition) is one of 118 or

so basic substances that everything (I mean everything) is made of.

• Elements are pure substances made of only one kind of atom.

IMPORTANT

• The four most important elements for life are:– Carbon– Hydrogen– Oxygen– Nitrogen

• (or, more accurately, “CHNOPS” – sulfur and phosphorus included)

• Fun Fact: If you wanted to buy all the chemicals in the human body in the right amounts, you’d only need about 97¢.

How Small Are We Talking?

• http://learn.genetics.utah.edu/content/begin/cells/scale/

• Scale of the Universe.lnk• Let’s add to the BioScale!

Mixing elements…

• Combining two or more elements in one substance creates a compound.– Example: Sodium and Chlorine together make

salt.• More on this later…

By the way…

• Element names are either written out fully or (in almost all cases) by a one- or two-letter abbreviation.

• Example:– Hydrogen or H– Lithium or Li

• If it’s two letters, the second letter is always lower case.

Subatomic Particles

• Well, it turns out that things get even smaller than atoms.

• There are the following three key subatomic particles:– Proton– Neutron– Electron

Aside: Sub-subatomic Particles

• Below the level of protons, neutrons, and electrons are other subatomic particles.

• Without going into too much depth:– Protons are made of three quarks, two “up”

and one “down.”– Neutrons are made of three quarks, two

“down” and one “up.”– Electrons are made of…electrons.

The Arrangement

http://www.bbc.co.uk/schools/gcsebitesize/science/images/19_1_atoms__isotopes.gif

• In each atom there is a central, dense nucleus composed of protons and neutrons.

• Surrounding the nucleus is a cloud of electrons.• In reality,

electrons are VERY FAR from the nucleus.

Subatomic Particles

• Protons– Location: Nucleus– Charge: Positive– Mass: 1 amu– Symbol: p+

– Discovered by: Eugen Goldstein

Subatomic Particles

• Neutrons– Location: Nucleus– Charge: None– Mass: 1 amu– Symbol: n0

– Discovered by: James Chadwick

Neutrons

http://24.media.tumblr.com/tumblr_m095muHVGa1rq6f8po1_500.jpg

Okay, one more…

• Why can’t you believe atoms?– Because they make up everything!

• Ishaan D. (September 2013)

Another, you ask?

• What did one atom say to the other atom?– Do these protons make my mass look big?

Subatomic Particles

• Electrons– Location: A cloud around

the nucleus, moving at high speeds

– Charge: Negative– Mass: 0 amu (so small it’s

rounded to virtually nothing)

– Symbol: e-

– Discovered by: JJ Thomson

Aside: Empty Space

• Okay, so you notice how most of the atom is empty space?• It turns out that nothing, really, is solid in our everyday

lives. Your chairs, your desks, your notebooks, YOU - they’re all mostly empty space.

• In fact, when two objects come in contact with each other, they actually don’t.– What I’m saying is you’re not actually touching your chairs right

now.• Two objects that “collide” are actually just experiencing

electrons repelling one another.– Without this force, a bowling ball would go through the pins.

• Cosmos – Atoms

Aside: You’re a Star!

• The Law of Conservation of Matter states that matter is never created nor destroyed.

• Here’s a weird thought…since atoms are never destroyed or created (only “recycled”), the same atoms that were in stars at the beginning of time are partially in YOU right now!

• The same goes for our ancestors.– It’s estimated that around 1 billion of your many

atoms once belonged to Shakespeare. Some of the rest may have come from Henry VIII or Julius Caesar or anyone else that died quite a while ago.http://upload.wikimedia.org/wikipedia/commons/thumb/c/c3/NGC_4414_(NASA-med).jpg/300px-NGC_4414_(NASA-med).jpg

Dmitri Mendeleev

• The inventor of the modern Periodic Table:

http://reich-chemistry.wikispaces.com/file/view/Dmitri_Mendeleev.jpg/98117907/Dmitri_Mendeleev.jpg

Trimmed his beard and hair

once a year.For reals.

Your Own Elements

• Mendeleev organized his table by a specific set of rules. We’re going to discover some of them on our own today.

• To the laptops!– One per pair, please.

To-Do List

• Visit the following website:– www.chemicalelements.com

• Click around on some of the elements. Be sure to look at the atomic diagram on the elements. Do you see a pattern here?

Practice

• Every element has different numbers of protons, neutrons, and electrons.

• With your partner, complete the Basic Chemistry Part 1 worksheet. Keep your eyes open for patterns…

• You have 8 minutes.

Atomic “Rules”

1. Is there a relationship between the number of protons and neutrons in an atom? What about protons and electrons?

2. Compare atomic number (that’s in the upper-right corner) to the number of protons in the element.

3. What about atomic mass? How might that be calculated?

For your notebooks…

• p+ = e-

– (normally)• Atomic Number = p+

– Unique to an element• Atomic Mass ≈ p+ + n0

– Approximately• Also for your notebook:

– Your very own periodic table!

Quick Review

• Here’s a good way to see how you’re doing with this information. Turn the person next to you and get ready…

Quick Review

• Number of electrons in Carbon?6

Quick Review

• Number of protons in Carbon?6

Quick Review

• Atomic mass of Oxygen?~16

Quick Review

• Number of protons in Oxygen?8

Quick Review

• Number of neutrons in (typical) Oxygen?8

Guiding Questions(Write these down)

1. Is it okay to use the number of electrons as a measure of atomic number?

2. What happens if you remove or add a proton?

3. What happens if you remove or add a neutron?

4. What happens if you remove or add an electron?

Building Elements?

• To get a better sense for how atoms are arranged, we’re going to build our own elements using one of two methods:– PhET – Build an Atom– ExploreLearning – Element Builder

PhET

• Visit this website (listed in my Bio Links page):– http://phet.colorado.edu/en/simulation/build-an-

atom• Once here, click “Run Now.”• When the applet loads, hit the + signs on the

right side next to “Symbol,” “Mass Number,” and “Net Charge.”

• Then, start building atoms by clicking and dragging subatomic particles to the appropriate places.

Element Builder

• [Log-in Instructions]

Element Builder

• Visit chemicalelements.com in a new window.• On Element Builder, click “Show element

name,” “Show element symbol,” and “Element notation” on the right.

Build Your Own Elements

• Build the following elements (don’t forget all the subatomic particles):– Hydrogen– Oxygen– Lithium– Carbon

Isotopes• Let’s explore Guiding Question #3 first, because

you probably saw the word “isotope” or “stable/unstable” a lot on the simulation.

• When you remove or add a neutron, you create a different isotope.

• Isotopes are atoms of the same element with different masses (different numbers of neutrons).

• Some are more common than others.– They’re often radioactive (unstable).

Radioactivity

• A “radioactive atom” is one whose nucleus is breaking down, releasing particles.– What those particles actually are is a bit

complicated – you don’t need to know this:• Alpha (α) Particle – 2 protons, 2 neutrons (He).• Beta (β) Particle – Neutron in nucleus changes to

proton and emits electron.

Isotopes• Isotopes change an atom’s atomic mass.• The weighted average of all isotopes of an

element corresponds to its atomic mass (thus the decimal point).– We will not be talking much about atomic mass this

year. Instead…• Generally, when you round the atomic mass or

simply add the number of protons and neutrons, you get the mass number.• Mass number = p+ + n0

• We can refer to isotopes in a few ways.– Example on next slide…

Famous Isotopes

• Uranium (Symbol U) typically has an atomic mass of:• 238

• Uranium has an atomic number of:• 92

• Therefore it has 92 protons/electrons. This means Uranium has how many neutrons?• 146 (because 238 - 92 = 146)

Famous Isotopes

• However, there is an unstable isotope of Uranium with a mass of 235. How many protons, neutrons, and electrons does it have?– 92 protons and 92 electrons– 143 neutrons

• To specify this kind of Uranium, we write it as:– U-235 (most common notation)– 235U– Uranium 235

• The mass, in other words, is written for you.• Why is it famous? Anyone?

Mass #

U-235

235U

• How “The Bomb” works, basically:– Radioactive isotope!– http://science.howstuffworks.com/nuclear-bo

mb3.htm– Video of Nuclear Explosion.

Famous Isotopes

• Carbon 14 (C-14 or 14C)– What’s carbon’s normal mass?

• 12– C-14 has two more n0.

• Used in carbon dating

http://www.purifiedbyfaith.com/CreationEvolution/Genesis5and11/Images/GeigerCounter.gif

InfoVids

• Isotopes and Carbon Dating – NOVA• Radioactivity

– TED: Steve Weatherell – Radioactivity – Expect the Unexpected

Isotopes

• What should you remember about isotopes?– They’re the same element, but a different

number of neutrons (and therefore a different mass number).

– Some are unstable/radioactive.– If you don’t see any mass numbers written next

to isotopes, assume they’re equal to the rounded atomic mass (and are common).

Isotopes

• Using your computer, create an Oxygen atom.– 8 protons, 8 neutrons, 8 electrons

• Now try playing around with the number of neutrons. Be sure to read the messages the simulation provides.

• What kinds of isotopes are possible?

Isotope

• Try the same process with Carbon.• About how many neutrons can you add or subtract

without making a non-existent or unstable element?– Adding or removing too many neutrons makes the atom

too unstable. Therefore, it may never form or stay together.

– Often, radioactive isotopes with short half-lives form. This basically means they break down really fast.

Guiding Question #4

• “What happens if you add or remove an electron?”– You create an ion.

• Ions are charged atoms where p+≠e-.– In other words, there is an imbalance between

the positive and negative charges in the atom.

Ions

• If an atom has more electrons than protons, it has a negative charge.

• If an atom has fewer electrons than protons, it has a positive charge.

• Example:– Hydrogen has one proton and one electron. If

we take away an electron, hydrogen becomes positively charged.

Determining Charge

• To figure out the charge on an ion, find the number of protons and electrons.

• Use the following formula:p+ – e- = CHARGE

• Example:• Lithium (atomic number 3) with 5 electrons:• 3 – 5 = Charge of -2 (Li 2-)

Writing Ions

• Here’s how to write Carbon with various charges:

• Notice “1” is never written, and the number is written before the sign.

Charge Notation0 C-1 C-

-2 C2-

+1 C+

+2 C2+

Etc… C3-, C4-, C3+, C4+

Building Ions

• Let’s build some ions:– H+

– Li+

– C4+

– O2-

• The only way to make ions is with electrons.

So, do you get this cartoon?

So that leaves…

• …Guiding Question #2.• If you somehow were to add or remove a

proton, that would change the atomic number.

• Changing the atomic number would change the element entirely.

Guiding Questions’ Answers

1. Is it okay to use the number of electrons as a measure of atomic number?

1 No, p+ ≠ e- if you are dealing with an ion.

2. What happens if you remove or add a proton?2. You change the element.

3. What happens if you remove or add a neutron?3. You change the isotope.

4. What happens if you remove or add an electron?4. You create an ion.

Basic Chemistry Worksheet

• Now, work on the back page of the Basic Chemistry worksheet (Part 2).

• Note that you should be using Mass Number now, instead of Atomic Mass.

• Remember:• Mass Number = p+ + n0

Closing today…

• On your computers, make sure you’re still in the PhET simulation.

• At the top, click the “Game” tab and try it out!

• Shut down and put the computer away when you’re done.

Closure

• TED: John Bergmann – Just How Small is an Atom?

Topics for Tomorrow

• Ions, isotopes, and bonds, oh my!