Download Discovery of electrons The size of an atom

This week:
If you have had chem 10,
What are atoms made of?
How do you name compounds and molecules?
the Physical Science division really needs
FAL leaders.
Please see me after class
Known natural laws in 1806:
Dalton’s atomic theory
1806
A good theory:
Law of conservation of mass:
Lavoisier 1785
Explains all available data
Predicts the future
Law of constant composition: 1700’s
Is usually ignored/disgraced
for a while
Law of multiple proportions:
Dalton
Natural Law: Statement of WHAT happens, not why
The size of an atom
Discovery of electrons
Figure 2.4
Figure 2.12
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Sub atomic particles
Amu: atomic mass unit
1 amu = 1.66054 x 10–24 g
A specific carbon atom has exactly 12 amu
All else is relative
AtomsAtoms
are are
really
small!
really small
Particle
Charge
Mass (g)
Mass
(amu)
Proton
+1
1.673 x10–24
1.007
Electron
–1
9.11 x10–28
5.5 x10–4
neutron
0
1.675 x10–24
1.008
Table 2.1
Atomic Force Microscopy
Heaviest atom is only 4x10–22 g
Only 1x10–10 m in diameter
Can’t see with optical microscopes
Gnat sized nucleus here, “outer” atom at Hwy 1
Mass spectrometer
Mass spectrum of Cl
Figure 2.14
Figure 2.13
Mass spec
2
Average atomic mass similar to
GPA calculation
3 unit class = C (2 grade points)
5 unit class = A (4 grade points)
Does GPA = 3?
Atomic symbols
• Atomic number = # of protons in nucleus.
• Mass number = # of p plus n in nucleus
At the Earth’s surface,
98.93% C with 12 amu
1.07% C with 13 amu
• Isotopes have the same # p but different # n.
• # of protons define the element
Calculate the average mass of C atoms
Concept Check-isotopes
Can two atoms have the same mass
but be different elements?
11
6C
12
6C
13
6C
14
6C
Isotopesymbols
symbols
Complete atomic
m ±
pX
X is atomic symbol
p is atomic number (# of ??)
m is mass number (# of ?? + ??)
Charge shows result of electrons lost or
gained
Cu-63 and Zn-63
Write atomic symbol for:
P, Zn, common ion of Na
Concept check: atomic
symbols
On Periodic Table
Atomic #
3
Li
Atomic symbol
6.941
Atomic mass
How many protons, neutrons and electrons
in Phosphorus-31?
What is the full atomic symbol for
P-31 if it has gained 3 e¯
How many protons, neutrons and electrons
in Pu-239?
What is the full atomic symbol for a 2+ ion that has
35 n and 28 e¯?
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Discovery
of Radioactivity
Radioactivity
α particles
β particles
γ rays
Three types of radiation were discovered in the early
1900’s by
He nuclei
electrons
high Energy X-rays
Henri Becquerel
Marie Curie
Ernest
Rutherford
Figure 2.8
Radioactivity is the process of nuclei
changing spontaneously into other nuclei
Nuclear decay is not affected by Temp, Pressure or time
Relative Penetration power
α
β
γ
Radiation is useful for sterilization,
killing cancer cells, and imaging tissues
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Types of compounds
Molecules and Molecular
diatomics
Compounds
• Compounds are two or more atoms bonded
together.
• The chemical formula of a compound indicates
– which atoms are found in the molecule, and
– in what proportion they are found.
• Compounds consisting of MOLECULES are
molecular compounds.
• Compounds consisting of IONS are ionic
compounds
• Molecules that contain two atoms of same element
bonded together are called diatomic molecules.
Predicting charge
Prediciting
charge
Ionic Compounds
Ions are charged atoms or molecules
Predicting Ionic Charge
Ionic compounds (such as NaCl) are usually
formed between metals and nonmetals.
Figure 2.23
Naming ionic compounds
Figure 2.22
Inorganic
Naming oxo
Naming
-anion
Compounds
Compounds
Cation (+ ion) name goes first
elemental cations are named as element
Anion (– ion) goes second
replace suffix of element with “ide”
GaAs
gallium + arsenic = gallium arsenide
examples from PT
Follow same rules for Polyatomic ions
Tranisition metal compounds: use Roman numerals
Figure 2.26
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Molecular compounds
Molecular compounds exist as individual molecules
Rules for naming
molecular compounds
• More metallic element’s name comes first
– Metallic character increases going down or left
– When in doubt, put carbon first, or oxygen last
Molecules stay intact when going from
solid to liquid to gas
Molecular formula: actual ratio of elements in molecule
C6H12O6
Empirical formula: smallest whole # ratio of elements
CH2O
• Add “ide” to the 2nd element’s name
• Use Greek prefixes to show how many atoms
are in the compound
• Drop one letter of “a-o” or “o-o”, but not “i–i”
– Example carbon monoxide, not carbon monooxide
Molecular compound prefixes
Examples
A compound with 2 N and 3 F
Nitrogen is to the left, so elements are in order:
Nitrogen fluoride
Add prefixes: dinitrogen trifluoride
Examples
Concept Check
Name:
N8Cl7
CBr4
S7 O5
What is formula of hexaphosporus pentaselenide?
What is name of O2F5?
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g
Naming
Naming Inorganic
Inorganic acids
acids
• Acids: a special class of compound,
• Have H in formula
• Names of acids are related to the names of anions:
-ide becomes hydro-….-ic acid;
-ate becomes -ic acid;
-ite becomes -ous acid.
a
c
i
d
s
examples
Figure 2.28
Some Simple Organic
Compounds
Alkanes
• Organic chemistry: the study of the chemistry of carbon
compounds.
• Alkanes contain only C and H and are called
hydrocarbons.
• The names of alkanes all end in the suffix –ane.
• Alkanes are named according to the number of C atoms
in their backbone chain:
• Methane has one C atom (CH4)
• Ethane has two C atoms (CH3CH3)
• Propane has three C atoms (CH3CH2CH3), etc.
Concept Check:
Ionic examples
Make and name ionic compounds:
Na and N
Cu2+ and NO3
Co3+ and CO32–
K and CN–
Ca and PO43–
Sr and MnO4–
Zn and SO32–
Know methane through hexane:
CH4
CH3CH3
CH3CH2CH3
CH3CH2CH2CH3
CH3CH2CH2CH2CH3
CH3CH2CH2CH2CH2CH3
What is name of this compound:
CH3CH2Cl
Write formulas for the following
compounds
Iron (II) hydride
Aluminum nitrite
Lead (IV) phosphate
Lithium oxalate
Manganese (II) perchlorate
Magnesium cyanide
Sodium hypochlorite
Chromium (VI) bicarbonate
Beryllium hydroxide
Zinc sulfite
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