Download 1 2.1 Atomic Structure and Subatomic Particles (p. 40) There are two

2.1 Atomic Structure and Subatomic Particles (p. 40)
There are two types of charge.
1. ___________________
2. ____________________
Electrons
In 1897 J. J. Thomson, using a cathode ray tube, measured the ratio of the charge-to-mass of the electron:
-5.6 x 10-9 grams/coulomb. (The coulomb, C, is the SI unit of charge.) Thomson is credited with the discovery
of the electron. George Stoney coined the term “electron” in 1891. Its origin is the Greek word for amber,
ήλεκτρον.
In 1909, R. A. Millikan, using his oil droplet experiment, determined the unit charge of an electron to be -1.60
x 10-19 C.
2.2 The Nuclear Atom (p. 43)
In 1911, Ernest Rutherford, using his “gold foil experiment”, proposed that the atom has a dense, positively
charged core which he called the “nucleus.” The electrons were envisioned to be someehow located in the
space around the nucleus. The term “proton” seems to have been coined by Rutherford, and first appears in
print in 1920. It was at this time that he proposed the possible existence of this type of particle within the atom.
Neutrons (p. 43)
In 1932, James Chadwick carried out experiments that detected neutral particles within the atom.
(The American chemist H.D. Harkins, coined the term "neutron" in 1921.)
SUMMARY (p. 44)
The atom is ______% empty space and is composed of three __________________ particles.
a.___________________
b.___________________
c.___________________
The atom is electrically ____________. This means that the number of ____________ is equal to the number
of ________________.
The electrons, composing less than ______% of the atom’s mass, ________ ___________ the nucleus.
In some atoms, the electrons are _________________ to move from one atom to another.
Protons and neutrons are located in the ____________.
The mass of the atom comes predominantly from the ___________.
The nucleus contributes less than _____% of the size of the atom, but ______% of the mass.
The electrons occupy most of the volume of the atom, but contribute very little mass.
Protons
When atoms lose electrons, they develop a ________________ charge.
The mass of the proton is 1.67262158 x 10-24 g.
The charge of the proton is __________ but ________________ in sign to that of the electron.
1
Particle Symbol Relative
Charge
Mass
Relative
Mass
(C)
(kg)
Mass
(amu)
Charge
0.0005485799
Electron
-1.60 x 10
-19
-31
9.11 x 10
1.007276
Proton
+1.60 x 10
-19
-27
1.673x 10
1.00866490
Neutron
-27
- - - - - - - - - - 1.675x 10
2.3 The Sizes of Atoms and Units Used to Represent Them (p. 44)
Mass is the quantity of matter in an object. The SI unit is the ________________(____), a unit about 2.2
pounds.
The SI unit of length is the __________ (____), a unit about 10% longer than a yard.
1 Angstrom (Å) = 10-10 m
Volume is a derived unit. 1 L = ____dm3 = ______ m3 or ___ cm3 = ___ mL
The SI for time unit is the second.
The SI unit for amount of a substance is the ________ (______).
1 mole =
The student must be able to carry out calculations based on Table 2.1 (p. 45).
Convert each of the following so that the power of ten is replaced by a prefix.
1. 3.88 x 10-2 g = ?
(3.88 cg)
2. 1.72 x 10-9 s = ?
(1.72 ns)
3. 8.06 x 103 L = ?
(8.06 kL)
4. 6.95 x 10-3 mol = ?
(6.95 mmol)
2
Use exponential notation to express each of the following in an appropriate SI base unit.
1.
2.33 µg = ?
(2.33 x 10-9 kg)
2. 4691 ns = ?
(4.691 x 10-6 s)
3. 55.2 cmol = ?
(5.52 x 10-1 mol)
SI Unit conversions
4 000 m = ? km
76,000 kg = ? Mg
1,500 mg = ? g
2,300 µs = ? ms
500 mL = ? L
12 pm = ? mm
2.4 Uncertainty and Significant Figures (p. 50)
There is uncertainty in all measurements. The digits recorded from a measurement will include both the certain
and the uncertain ones. These digits are called significant figures. In general, the greater the number of
significant figures in a measurement, the greater is the certainty of the measurement.
Significant Figures
1. All Non-zero digits are significant.
2. Zeros may or may not be significant.
a. Leading zeros (zeros to the left of a digit) are not significant.
b. Captive zeros (zeros between non-zero digits) are significant.
c. Trailing or terminal zeros (zeros to right of number) are significant only if the number contains a decimal
point, otherwise they are not.
3. Exact numbers contain an infinite number of significant figures.
Rules for Significant Figures in Calculations
1. When multiplying or dividing, the answer has the same number of significant figures as the value in the
operation with the least number of significant figures.
2. When adding and subtracting, the answer has the same number of decimal places as the value in the
operation with the least number of decimal places.
3. Exact numbers have no bearing on the number of significant figures and are not considered when
determining the number of significant figures in an answer.
3
Perform the following operations and give answers in the correct number of significant figures.
A. 4.184 x 100.62 x (25.27 - 24.16) = ?
E. 0.1654 + 2.07 - 2.114 = ?
B.
8.925 - 8.904 x 100 = ?
8.925
F.
C.
(9.04 - 8.23 + 21.954 + 81.0) / 3.1416 = ?
G.
D.
9.2 x 100.65 = ?
8.321 + 4.026
H.
8.27(4.987 - 4.962) = ?
9 .5 + 4.1 + 2.8 + 3.175 = ?
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9.025 - 9.024 x 100 = ?
9.025
Answers: A. 467.; B. 0.24; C. 33.03; D. 75.; E. 0.12; F. 0.21; G. 4.9; H. 0.01
2.5 Atomic Numbers and Mass Numbers (p. 53)
2.6 Isotopes and Atomic Weight (p. 56)
[Power Point presentation]
4
2.5 Atomic Numbers and Mass Numbers
The atomic number (Z)
= the ____________ on the nucleus
= the number of __________ in the nucleus
= the number of ___________ in the atom
21
Atoms of the same element have the same number
of __________ in the nucleus.
11
The mass number (A) = the sum of the number
of protons and ________________in the nucleus
Na
____ protons, ____ electrons, and ____ neutrons
A – Z = number of ________
Isotopes are atoms whose nuclei have the same
atomic number but different mass numbers;
that is the same number of protons but
different number of neutrons.
Species
23Na
22Na
Protons
__
Neutrons
________=__
__
________=__
35Cl
__
________=__
37Cl
__
________=__
Lagniappe
Atoms are electrically __________.
Ions are _________ particles.
_______ are positively charged ions.
_______ are negatively charged ions.
Z - charge = _______________
Na1+
_____________________
S2-
____________________
2.6 Isotopes and Atomic Weight
Atomic weight is related to the standard of
carbon-12. By definition, an atom of
carbon-12 has exactly 12 amu. Masses of
all other atoms are relative to this scale.
There are two naturally occurring
isotopes of carbon on earth: 12C and 13C.
12C has a mass of 12 amu
13C
has a mass of 13.0034 amu
1
The atomic weight (molar mass)
given at the bottom of a symbol, is the
weighted average of the masses of the
naturally occurring isotopes of that
element.
The atomic weight is the sum of the
isotope contributions.
Isotope contribution =
=(
)x(
12C
has a natural abundance of 98.892%,
while the natural abundance of 13C is 1.108%.
12C
13C
has a mass of 12 amu
has a mass of 13.0034 amu
The atomic mass of carbon is:
)
Naturally occurring chlorine is a mixture
of two naturally occurring isotopes: 35Cl
which has an abundance of 75.77% and
an isotopic mass of 34.969 amu, and
37Cl with an abundance of 24.23% and
an isotopic mass of 36.966 amu.
What is the atomic mass of chlorine?
2
2.7 Amounts of Substances – The Mole (p. 59)
Mole (mol)
The SI unit for amount of substance is the mole. It is a counting quantity for particles such as atoms or
molecules, or for other chemical entities. Thus, “the amount of water in a beaker” is the number of water
molecules in the beaker and not the mass or the volume of water.
1 mole (____) = 602,213,673,600,000,000,000,000 = ________________________
-
A mole is the amount of substance in a sample that contains as many elementary entities as the number of
atoms in exactly 12 g of C-12.
-
The mass of one mole in grams is numerically equal to the molar mass. The mole is so defined that a
sample of an element with a mass equal to its atomic mass in grams is one mole of that element.
How many years would it take for the world’s population to spend a mole of dollars at a
rate of $1000 per second?
2.8 Molar mass and Problem Solving (p. 60)
1. How many moles are in 0.100 g of silicon? [3.56 x 10-3 mol]
2. What is the mass of 5.00 moles of silver? [5.39 x 102 g]
3. How many atoms are in 5.23 x 10-4 mol of potassium? [3.15 x 1020]
4. How many moles are in 9.83 x 1022 atoms of mercury? [0.163 mol]
5. How many atoms are in 3.50 g of iron? [3.77 x 1022 atoms]
6. What is the mass of 8.50 x 1024 atoms of lead? [2.92 x 103 g]
7. How many electrons are in a 1.000 g sample of tungsten? [2.423x1023]
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