When Atoms

Change…

What we KNOW…

• Atoms on the periodic table are neutral.

• Atoms are neutral because they have the same number of protons as electrons.

• protons  have a positive charge.

• neutrons  have no charge.• electrons have a negative charge.

What we Also need to KNOW…

• The identity of an atom is determined ONLY by the number of protons.

• For example… If I tell you there is an atom with 3 protons… you know it’s a Lithium atom.

• What about 8 protons, 13 protons, 79 protons???

What happens if the number of neutrons

change???If an atom gains Neutrons…1. The mass increases by 1 for every neutron added. 2. The charge remains neutral. (Neutrons don’t have

a charge.) 3. The number of protons and electrons stay the

same.

If an atom loses Neutrons…1. The mass decreases by 1 for every neutron taken

away. 2. The charge remains neutral. (Neutrons don’t

have a charge.)3. The number of protons and electrons stay the

same.

What happens if the number of neutrons

change???If an atom gains Neutrons…1. The mass increases by 1 for every neutron

added. 2. The charge remains neutral. (Neutrons don’t have

a charge.) 3. The number of protons and electrons stay the

same.

If an atom loses Neutrons…1. The mass decreases by 1 for every neutron

taken away. 2. The charge remains neutral. (Neutrons don’t

have a charge.)3. The number of protons and electrons stay the

same.

The atom is now called an ISOTOPE!

When atoms gain or lose neutrons!

ISOTOPE EXAMPLE

                                           

   

                                                             

     Hydrogen AtomHas a mass of 1 and an atomic number of 1

Hydrogen Isotope

Has a mass of 2 and an atomic number of 1

ISOTOPE NOTATION

We communicate that we have an isotope by using the Atomic Symbol of the isotope followed by the “NEW” mass number.

ISOTOPE NOTATION Li-7Ex: An Isotope of Lithium is:

Li - 6

Isotope INVENTORY

Completing a particle inventory for an Isotope is almost the same as the neutral atom EXCEPT we USE THE “NEW” MASS NUMBER to calculate neutrons.

Ex: Li-63p+ (since it’s Lithium!!!)3e- (since they are still equal to p+)3n

Isotope Practice• Ca atom has a mass of 40.• The isotopes for Ca are: • Ca-42, Ca-43,Ca-44, Ca-46, & Ca-

48.• 1.) How many neutrons are in a Ca

atom and each of its isotopes?

2.) What are the differences and similarities between the Ca atom and its isotopes?

Isotope PracticeCa atom has a mass of 40. (atomic # =20)The isotopes for Ca have masses of 42,43,44,46, & 48.

1.) How many neutrons are in a Ca atom and each of its isotopes?

(Ca ATOM: 40 – 20 = 20n)(ISOTOPES: 42-20=22n, 43-20=23n, 44-20=24n, 46-20=26n, 48-20=28n)2.) What are the differences and similarities between

the Ca atom and its isotopes? Similarities Differences

(All have 20 p+ all have 20 e- all neutral

all are Calcium)

(The # of neutrons is different, masses are all different.)

• Everyone gets 7 blue, 7 red, 7 yellow• Red = Protons• Blue = Neutrons• Yellow = Electrons• Play 1-5 marbles per turn.

Number of neutrons and protons

Number of protons and electrons

Subtract the two to find the number of neutrons

The Atom Building Game

Everyday Uses of IsotopesSmoke Detectors and Americium-241

What most consumers don't know is that many of these units contain a small amount of americium-241. By utilizing the radioactive properties of this material, smoke from a fire can be detected at a very early stage. This early warning capability has saved many lives. In fact, studies have shown that 80% of fire injuries and 80% of fire fatalities occur in homes without smoke detectors.

Carbon-14 DatingRecalling that all biologic organisms contain a given

concentration of carbon-14, we can use this information to help solve questions about when

the organism died. When an organism dies it has a specific ratio by mass of carbon-14 to carbon-12

incorporated in the cells of it's body. At the moment of death, no new carbon-14 containing molecules are metabolized, therefore the ratio is

at a maximum. After death, the carbon-14 to carbon-12 ratio begins to decrease because carbon-14 is decaying away at a constant and predictable rate. Remembering that the half-life of carbon-14 is 5700 years, then after 5700 years half as much carbon-14 remains within the organism.

Food Irradiation

Food irradiated by exposing it to the gamma rays of a radioisotope -- one that is widely used is cobalt-60. The gamma rays pass through the food to destroy many disease-causing bacteria as well as those that cause food to spoil. It’s not strong enough to change the quality, flavor or texture of the food. The food never comes in contact with the radioisotope and is never at risk of becoming radioactive!

Reviewing IsotopesWhat are isotopes gaining or losing?

Here is an Atom of Oxygen (how many neutrons?)

Atomic Mass=16 These are isotopes of Oxygen

O-17 O-18

So…How many neutrons does each isotope of Oxygen NOW have?

8 neutrons

Neutrons!

10N9N

Isotope Practice

1.)How many neutrons are in each of Zinc’s isotopes? Zn-65

Zn-64____ Zn-67_____ Zn-70____

2.) What are the differences and similarities between the Zn atom and its isotopes? Set-up a “T” Chart

Isotope Practice

1.)How many neutrons are in each of Zinc’s isotopes? Zn-65

Zn-64____ Zn-67_____ Zn-70____

2.) What are the differences and similarities between the Zn atom and its isotopes?

34 4037

Similarities Differences

• All have 30 p+ all have 30 e-

• all neutral • all are Zinc

• # of neutrons is different• masses are all different

Isotope Warm up

1.)How many neutrons are in each of Strontium’s isotopes?

Sr-84____ Sr-86_____ Sr-87____

Answers:Sr-84 46Sr-86 48Sr-87 49

Quiz QuickIsotopes gain or lose…

A. electronsB. protonsC. neutronsD. nuclei

When an atom gains neutrons, its charge

changes.A. TrueB. False

When an atom gains neutrons, the number of protons and electrons do

not change.A. TrueB. False

The only subatomic particles that never change

are…A. Valance

electronsB. ProtonsC. ElectronsD. Neutrons

What happens if the number of electrons

change???If an atom gains electrons…1. The charge becomes negative. (There are more

negative e- than positive p+ now!)2. The mass stays the same (electron’s mass = 0). 3. The number of protons and neutrons stays the

same.

If an atom loses electrons…1. The charge becomes positive. (There are less

negative e- than positive p+ now!)2. The mass stays the same (electron’s mass =0).3. The number of protons and neutrons stays the

same.

What happens if the number of electrons

change???If an atom gains electrons…1. The charge becomes negative. (There are

more negative e- than positive p+ now!)2. The mass stays the same (electron’s mass = 0). 3. The number of protons and neutrons stays the

same.

If an atom loses electrons…1. The charge becomes positive. (There are

less negative e- than positive p+ now!)2. The mass stays the same (electron’s mass =0).3. The number of protons and neutrons stays the

same.

The atom is now called an ION!!!

When atoms gain or lose electrons!

*Ions are charged particles!Ions form so that unstable atoms can bond with other unstable elements to become a stable

substance!

Charged Ions

Anion (-) Negatively charged ion.

Cation (+) Positively charged ion

Quick QuizIf an atom loses electrons,

its mass changes?A. TrueB. False

Ions gain or lose…

A. isotopesB. protonsC. neutronsD. electrons

Gaining electrons causes atoms to…

A. Gain more mass

B. Have a chargeC. Stay neutralD. Lose mass

ION EXAMPLE

H+ is a positive

hydrogen ION

H: Is the neutral

hydrogen atom

H- : is a negative hydrogen

ION

Ion PracticeNaBeI

CaSbSPC

Na+1

Be+2

I-1 Ca+2

Sb-3

S-2

P-3

C+/-4

Ion Worksheet AnswersLi +1

Br -1

Mg +2

B+3

F -1

N -3

Cl -1

K +1

Ba +2

Te -2

Sn -4

As -3

Si +/-4

O -2

Al+3

Ion Worksheet ColoringLi +1

Br -1

Mg +2

B+3

F -1

N -3

Cl -1

K +1

Ba +2

Te -2

Sn -4

As -3

Si +/-4

O -2

Al+3

What patterns did you notice from coloring your ions on the periodic

table? *hint* there is more than one!

• The families where the same color.• The families had the same ionic

charge.• Metals have a positive charge.• Non-metals have a negative charge.• Metals lose electrons.• Non-metals gain electrons.

PracticeDraw the Bohr models for the following elements and find the ionic charges for each.

RbSrBi

Rb

Sr

Bi-3

+2

+1

How is the neutral(no charge) atom Se and it’s isotope Se-78

similar and different?(Set up a “T” chart)

SimilarSame element

Same # of protonsSame # of electrons

Same charges

DifferentDifferent masses

Different # of neutrons

How are isotopes and ions similar and different? (setup a T chart)

(hint* think about particles, masses and charges) Similarities

Same number ofprotons only!

DifferencesDiff Masses

Diff Number ofneutrons

Diff ChargesDiff Number of

electrons

PracticeDraw the Bohr models for the following elements and find the ionic charges for each.

GaSrPb

Ga

Sr

Pb-4

+2

-5

Patterns on the

Periodic Table

+1

+2

+3

+/-4 -3 -1-2

0

Ionic Charg

es

Valence Electron

s

1 Shell

3 Shells

4 Shells

5 Shells

6 Shells

7 Shells

2 Shells

Period 1

Period 2

Period 4

Period 3

Period 5

Period 6

Period 7

Energy Shells of Atoms

Families/Groups have a lot in common…

• We now know that elements in a group all have the same # of valence e-.

• We also now know they all form ions with the same charge.

• But…there are a lot of other properties that elements in a family also share!

• Such as…Atomic Width, Ionization Energy, Electronegativity and reactivity.

Atomic Radius (Width)• Atomic radius is simply the radius (width) of the

atom, an indication of the atom's volume. • Periods - atomic radius decreases as you go

from left to right across a period. • Why?• Stronger attractive forces in atoms (as you go

from left to right) between the opposite charges in the nucleus and electron cloud cause the atom to be 'sucked' together a little tighter.

• Largest atomic species are those found in the SW corner of the periodic table.

Atomic Radius (Width)• Groups - atomic radius increases as you

go down a group. • Why? • There is a significant jump in the size of

the nucleus (protons + neutrons) each time you move from period to period down a group. Additionally, new energy levels of elections clouds are added to the atom as you move from period to period down a group, making the each atom significantly more massive, both is mass and volume.

Ionization Energy

• Ionization energy is the amount of energy required to remove the outmost electron. It is closely related to electronegativity.

• Group - ionization energy decreases as you go down a group.

• Why? • The shielding affect makes it easier to

remove the outer most electrons from those atoms that have many electrons (those near the bottom of the chart).

Electronegativity• Electronegativity is an atom's 'desire' to grab

another atom's electrons. • Period - electronegativity increases as you go

from left to right across a period. • Why? • Elements on the left of the period table have 1

-2 valence electrons and would rather give those few valence electrons away, as a result, they have low electronegativity.

• Elements on the right side of the period table only need a few electrons, so they have strong desire to grab another atom's electrons.

Electronegativity

• Electronegativity is an atom's 'desire' to grab another atom's electrons.

• Group - electronegativity decreases as you go down a group.

• Why? • Elements near the top of the period table

have few electrons to begin with; every electron is a big deal. They have a stronger desire to acquire more electrons. Elements near the bottom of the chart have so many electrons that loosing or acquiring an electron is not as big a deal.

Reactivity• Elements become more reactive as

you go down a group on the left side • And more reactive as you go up a group

on the right side!

• Reactivity refers to how likely or vigorously an atom is to react with other substances.

• Based on this, where are the most reactive elements found on the periodic table?

Bottom left corner (Fr) and top right corner (F)

What are (7) things you can now predict about the element Iodine (I),

based on where it is located on the Periodic Table?

1. It has 7 valence electrons2. It has 5 energy rings/shells3. It is a non-metal4. It’s gaining 1 electron5. It’s ionic charge is -16. Less reactive than Br and Cl7. But it’s more massive than Br

and Cl

Properties of Non-metals

• No luster• Brittle• Not ductile • Not malleable

(dull)

(breaks easily)

What can you now tell me about the element Nitrogen (N) and

Potassium (K), based on where they are located on the Periodic Table?

(think about shells, valence e’s, charges, metal/non-metal, gaining/losing e’s)

Potassium

• 1 valence electron• It has 4 energy rings• It is a metal• It’s losing 1 electron• It’s ionic charge is +1

Nitrogen•5 valence electrons

•It has 2 energy rings

•It is a non-metal•It’s gaining 2

electrons•It’s ionic charge is -

3

You are the bus driver. At your first stop, you pick up 29 people. On your second stop, 18 of those 29 people get off, and at the same time 10 new passengers arrive. At your next stop, 3 of those 10 passengers get off, and 13 new passengers come on. On your fourth stop 4 of the remaining 10 passengers get off, 6 of those new 13 passengers get off as well, then 17 new passengers get on. What is the color of the bus driver's eyes?