Name ____________________________ Block ______ Date __________________

 

 

 

 

 

Those Magic Changes

 

Chem Catalyst:

What particles in the atom do you think can change numbers without changing the identity of the element.  Explain your answer.

 

 

 

 

 

 

 

 

 

 

Isotopes protocol:

Draw a graph on full page sized graph paper.       

Label the X axis grams and scale from 1-2 grams.

Label the Y axis “number of pennies”

Grab 20 pennies.

Mass each penny to 0.01g precision.

Graph the masses on a scatter plot graph. (i.e. place each penny on the graph above the corresponding mass.  Make a column of pennies if you have more than one of the same mass.

 

Hypothesis and rationale

What shape do you expect to see in the graph of the pennies? Please give a detailed rationale, check with me, then run the lab.

 

 

 

 

 

 

 

 

Notes – Ions and Isotopes

 

IONS ARE ATOMS THAT HAVE GAINED OR LOST ELECTRONS

           

            Why do atoms gain or lose electrons?

            It turns out that electrons are most stable (lowest energy) when there are 8 in the outer shell.

                        Group VIIIA (far right) all have 8 in their outer shell.  (These are the NOBLE GASES)

                        All other atoms will gain or lose electrons to look like the noble gases and be more stable.

                                    We call this NOBLE GAS ENVY (NGE)

                       

            What will be the charge on an ion of Chlorine?

                   Chlorine has two choices to become an ion.  It can gain 1 electron to look

like argon or lose 7 electrons to look like Neon.

 

Atoms always choose the lowest number.

 

Chlorine will gain 1 electron and have a –1 charge.

 

          What will be the charge on an ion of Be?

                   Berilium has two choices, it can lose 2 electrons to look like He or gain 6

electrons to look like Ne.

 

Atoms always choose the lowest number.

 

Berilium has a +2 charge.

 

          What will be the charge on carbon ions?

                   Carbon can lose 4 electrons to look like He or gain 4 to look like Ne.

                   If the numbers are the same, an atom will lose electrons if it is bonded to

elements on its right and gain electrons if it is bonded to elements on its

left.

 

 

ISOTOPES ARE ATOMS OF THE SAME ELEMENT THAT HAVE DIFFERENT NUMBERS OF NEUTRONS.

 

            Remember that the mass of an atom is

                        Mass  =  Protons  +  Neutrons.

 

            If neutrons can change, then isotopes can be named by the element and its mass.

 

                        Carbon can be Carbon – 12, carbon – 13, or Carbon – 14 depending on how many

neutrons are present.

 

 

            Ex. How many neutrons are in Carbon 13?

                      Mass       = 13

                   - Protons    = 6

                      Neutrons = 7

 

            Isotopes can be identified in two ways.

                        Isotope name = Carbon – 13.  The 13 is the mass of the isotope.

                        Chemical symbol  =  ¹³C.  The mass number is in the upper left corner.

 

                        Mass on the periodic table is “AVERAGE ATOMIC MASS” and averages all the atoms

                        of that element in the universe.

 

            Radioactivity is caused by unstable isotopes.

                        Example – Carbon is stable with 6 neutrons, not stable with 8 neutrons. 

                        Unstable nuclei will kick out particles until they reach more stable structures.

                        Pages 112 and 113 describe this in more detail.

 

 

 

HONORS EXTENTION:

            Calculate the average atomic mass of an element.

Find specific examples from the LBC lab.

 

            Isotope A – mass x percent abundance = weighted %

          Isotope B – mass x percent abundance = weighted %

 

          Add weighted % of all isotopes to get average atomic mass. 

(This should be very close to the number on the periodic table.)

 

Notes – Ions and Isotopes

 

IONS ARE:

           

Why do atoms gain or lose electrons?

 

 

NOBLE GAS ENVY (NGE):

                       

 

What will be the charge on an ion of Chlorine?

          a.

 

b.

 

c.

 

 

What will be the charge on an ion of Be?

          a.

 

          b.

 

 

          c.

 

         

 

What will be the charge on carbon ions?

          Why is Group IV special?

 

 

 

How do you know if it is positive or negative?
ISOTOPES ARE:

 

            Remember that the mass of an atom is

                        Mass  =

 

            If neutrons can change, then isotopes can be named by the element and its mass.

 

Carbon can be:

 

 

            Ex. How many neutrons are in Carbon 13?

 

 

 

 

            Isotopes can be identified in two ways.

                        Isotope name =

                        Chemical symbol  = 

 

            “AVERAGE ATOMIC MASS”

           

 

            Radioactivity is:

                        Example –

                        Unstable nuclei:

                        Pages 112 and 113 describe this in more detail.

 

 

Key to Homework p 122-3

 

 

3. A

 

4. C

 

5. b

 

9. d

 

10. c

 

15. false- zero

 

16. false – atomic number

 

17. false – ion

 

18. true

 

22. protons – positive charge, mass of 1amu, in nucleus,           

neutrons – no charge, mass of 1amu, in nucleus              

electrons – negative charge, mass 1/2000 of proton, in clouds around nucleus

 

27. particles deflected toward positive plate (green arrow) are negative charge

particles deflected toward negative plate (orange arrow?) are positive charge

particles not deflected are neutrons or atoms (no charge)

 

30. Molybdenum-96 is far more common (assuming it exists!).