Download CA #1 Other Topics - Wando High School

CA #1 Other Topics
Atomic Radii: Comparing the Size of
Atoms of Deferent Elements
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After H and He…
Fluorine is the smallest atom (top right)
Francium is the largest (bottom left)
This general trend is true for most elements.
Mark this trend on your colored periodic charts.
F
Fr
Atomic Radii: Which atom is bigger?
• Br or F? P or S?
• Does Strontium or calcium have a larger
atomic radii?
• Sodium or chlorine?
• You make up two more…
Atom vs Ion size
• If an atom GAINS electrons it will logically
become larger. So the ion formed will be
bigger than the original atom.
• Ex. If Flourine gains an electron it will become
the F-1 ion. The fluorine ion will be bigger than
its original atom.
• Will sulfur’s ion or atom be bigger?
• The atom will gain 2 electrons so the S-2 ion
will be bigger than the atom was.
Atom vs Ion size
• If an atom Loses electrons it will logically
become smaller. So the ion formed will be
smaller than the original atom.
• Ex. If lithium loses an electron it will become
the Li+1 ion. The ion is smaller than the original
atom.
• Will Calcium’s ion or atom be bigger?
• The atom will lose 2 electrons so the Ca+2 ion
will be smaller than the atom was.
Answer the following…
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Is nitrogen’s ion or atom bigger?
Is magnesium’s ion or atom bigger?
Is aluminum’s ion or atom bigger?
Is iodine’s atom or ion bigger?
Ionization energy (a brief introduction)
• It is harder to pull candy away from a strong kid
than a smaller one (usually)
• Likewise, it is harder to take electrons away from
some atoms than others. (outermost electrons)
• If an atoms holds on stubbornly to its electrons,
it will take more energy to pull those electrons
away from the atom.
• This energy is known as the 1st ionization energy.
1st ionization Energy Trend
• Fluorine has the highest 1st ionization energy.
• This means it’s hard to steal electrons from it. Why
is this logical?
• It wants to gain electrons, not give them away!
• Francium is the lowest (easy to steal from). Why?
• Put this general trend on your Periodic Chart.
• Which has the higher 1st ionization energy?
• In other words- which would take more energy to
steal from?
• Na or K? Ca or Sr? Cl or F? P or As?
• Na or Mg? Se or Br? Rb or Sr? Te or I?
Shielding Effect (a brief introduction)
• Young animals that wander far from mommy are in
more danger from predators than the ones that are
close. Why is this?
• Likewise, electrons that are farthest from the nucleus
are more likely to be taken. Electrons in the outermost
energy level don’t feel the pull of the nucleus as much.
• They are more likely to be the electrons taken. Why?
• All the electrons BETWEEN the nucleus and the
outermost elections also BLOCK THE PULL of the
nucleus. This is known as the shielding effect.
• Class demo with people as electrons- teacher as
nucleus.
• Also need a thief.
Which atoms will have the most
shielding?
• Big Atoms have most shielding effect? Why?
• The outermost electrons are far away from the
nucleus.
• Which of the following has the most shielding
effect?
• Na or K? Ca or Sr? Cl or F? Ag or Pa?
• Rb or Sr? Pb or Lu?
Basic Metrics Review
• Name an object about the size of the
following.
• Meter (m)
• Centimeter (cm)
• Kilometer (km)
• Millimeter (mm)
• Now put these in order (use prefixes only)
from biggest to smallest.
Quickly Converting in the Metric
• King Henry loves to convert.
• King Henry Died Monday Drinking Chocolate Milk
kilo, hecto, deca, meter or liter, deci, centi, milli (Commonly used are underlined)
For example for meters and liters…
• Km hm dam (meter) dm cm mm
• Kl hl dal (liter) dl cl ml
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Convert 25 mm to meters
Convert 437.00 cm to meters
Convert 25.7888 liters to ml
Convert .000564 meters to mm
Convert 678.200 cm to Km
Convert 26 Km to cm
A few things that will help on CA #1
• Ionically bonded compounds/(called Ionic
compounds) vs Covalently bonded
compounds (often called covalent molecules
or covalent compounds).
• Ionically bonded compounds have
ions/charges holding them together.
• Ex CaCl2 NH4F- this like all metals BUT…
• Covalent molecules/compounds have all nonmetals. They don’t have ions and will have
prefixes in their names.
• EX. OF2 SC4 name them both (hint:Carbide)
Why do elements in the same family
have similar chemical properties?
• They become stable the same way!
• That is, Within the same family, elements lose
or gain the same number of electrons when
they become stable. So the are chemically
similar in properties.
Cation vs Anions
• Cations are postive ions and are written first in
ionic compounds.
• Ex.
• Anions are negative ions and are written last
in ionic compunds
• Covlent compounds
• Don’t have cations or anions!
Dependent vs independent
variable
X or Y axis?
• Independent- the one the scientist controls
that causes a change (on X axis when graphing).
• Dependent- the variable that is affected by
the change in the impendent variable (on Y
axis when graphing).
Precision Vs Accuracy
• Precision: Getting the same answer from an
measurement instrument over and over. A
precise instrument will give the same
measurement every time.
• Accuracy: Getting the CORRECT (accepted)
answer is getting an accurate measurement.
(Just because an instrument keeps giving you
the same measurement does not mean that
measurement is correct! This would be precise
but not accurate)
Significant Figures
• Precise measurement-
Rounding Final Answers
(Using Significant Figures)
Significant Figures/Digits
• Which numbers in a measurement are
significant?
• Ex. .045 g of Au
• How to determine which numbers are
significant figures…
• THE UNITED STATES Method
• Draw the US- the number inside
• Label Pacific – Atlantic
• P= decimal is present A= decimal is absent
Decimal Present: Rules
• If a decimal is PRESENT…
• 1) Start from the P side and approach the
number (the left)
• 2) Keep going until you hit the first non-zero
number- stop before that number.
3) This first non-zero digit and all numbers after
are significant digits! (including zeros)
How many Sig. Figs.?
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.0034 g Ag has…
2 sig. figs.
224.00 mg Ca…
5 sig. figs.
.004000 L of oxygen…
4 sig. figs.
234.0 g Sr…
4 sig figs
.0000000000003 g Ti… (12 zeros)
1 sig. fig.
Decimal Absent: Rules
• If a decimal is Absent…
• 1) Start from the A (the right) side and
approach the number
• 2) Keep going until you hit the first non- zero
number- stop before that number.
3) This first non-zero digit and all numbers to the
left are significant digits! (including zeros)
How many Sig. Figs.?
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234 g Ag has…
3 sig. figs.
2240 mg Ca…
3 sig. figs.
43600 L of oxygen…
3 sig. figs.
200000000 mg Ti… (8 zeros)
1 sig. fig.
Rounding Answers for Multiplication
and Division Problems
• Rule:
• The final ROUNDED answer must have the
same number of significant figures as the
measurement with the FEWEST sig figs in it.
4 sig figs
2 sig figs
• Ex. 23.40 m x 1.4 m =
• Cal= 32.76
• R= 33
SSN= 3.3 x 101 m2
Try a few
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Ex. .00340 m x .078 m =
Cal= .0002652 OR 2.652 X 10-4
R= .00027 Or 2.7 X 10-4
SSN = 2.7 x 10-4 m2
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Ex. 34050 g x 7860 L =
Cal= 267633000
R= 268000000
SSN = 2.68 x 108gL
More Practice
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Ex. 7.18 g/ 2.300 g =
Cal= 3.12173913
R= 3.12
SSN = 3.12 x 100 (no units)
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Ex. 34.00 m / .0200 g =
Cal= 1700 (2 sig. figs. currently)
R= (Can’t do it without SSN)
SSN = 1.70 x103 m/g
Round each cal. to
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A) 3.2354 g
B) 3.45 g
C) 67 g
D) 4.5 g
E) 2395 g
F) 749399 g
G) 749671 g
H) .00432 g
I) .03476 g
J) 3496.983 g
K) .088654 g
2 sig figs,
then 3 sig figs
R= 3.2 g
R= 3.5 g
R= 3.24 g
R= 3.45 g
R= 67 g
R= 4.5 g
R= 67.0 g
R= 4.50 g
R= 2400 g
R= 750000 g
R= 2.40 x 103 g
R= 749000 g
R= 750000 g
R= .0043 g
R= 7.50 x 105 g
R= .00432 g
R= .035 g
R= .0348 g
R= 3500 g
R= 3.50 x 103 g
R= .089 g
R= .0887 g
Adding and Subtracting measurements
• Rule:
• The final ROUNDED answer must have the
same number of digits PAST THE DECIMAL as
the measurement with the Fewest Past the
Decimal.
Ex. 7.180 g + 2.3000 g = (fewest is 3 past decimal)
Cal= 9.48 (this is only 2 past the decimal)
R= 9.480g (3 past)
SSN = don’t worry about for now
Ex. 344.00 m - 5.0 m =
Cal= 339
R= 339.0 m
Ex. 14 g + 1.0200 g =
Cal= 15.02
R= 15g
Ex. 23.14g + 2.5g=
Cal= 25.64
R= 25.6 g