Take out reading check andDo Now:
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Take out reading check andDo Now:1. If 100,000,000 copper atoms were placed
side by side, they would form a line 1 cm long. A)What is the number of atoms written in
scientific notation.B)What is the diameter of 1 copper atom?
0.0000001 cm
So how small is the atom?
•Very small!• Smallest particle of an element that
keeps the element’s properties
About 400 B.C. Democritus• a Greek philosopher• Proposed matter was composed of
tiny, indivisible particles called “atomos”
• origin of the word atom
Late 1700’sAntoine Lavoisier
Joseph Proust
Proposed Law of Conservation of Matter - matter cannot be created nor destroyed
Proposed Law of Definite Composition - a given compound always contains the same elements in the same proportions by mass
John Dalton’s Atomic Theory
• Each element is composed of tiny indivisible particles called atoms.
The atoms of any one element differ from those of any other element.
• Atoms of different element combine in simple whole-number ratios to form compounds.• In chemical reactions, atoms are neither created nor destroyed. Atoms are rearranaged.
Late 1800’s J.J. Thomson
• Experimented with cathode ray tubes (CRTs)
Battery
+
Cathode Anode
-______
+______
+ - + - + - +
+ - + - + -
• Concluded cathode ray composed of negative particles - electrons
J. J. Thomson
• Unable to measure mass of electron, but found ratio of electron’s electrical charge to its mass - 1.76 x 10
8 Coulombs/gram
• Proposed Plum Pudding Model
DO NOW!
• What were Dalton’s and Thompson’s contributions to atomic theory?
• Performed Oil Drop Experiment in 1909Robert Millikan
• Found charge of electron to be 1.6 x 10-19
Coulombs• Calculated mass of electron to be ~ 9.1 x 10-28 g
• In 1896, Henri Becquerel accidentally discovered radioactivity while studying uranium salts
Radioactivity
• Spontaneous emission of energy from unstable nuclei•One type of radiation is alpha radiation. It is positively charged.
• Performed Alpha Particle Scattering Gold Foil ExperimentErnest Rutherford in 1909
• Findings ??? 1. Atoms mostly empty space2. Atom contains a nucleus
3. Nucleus positively charged
What else is in the atom?Proton –
Neutron - Discovered by Chadwick in 1932
Discovered by Rutherford in 1918 by
Do NOW!
1. What is an atom?2. What subatomic particles does it
contain?3. Distinguish between the subatomic
particles.4. What is an isotope?5. What is an ion?
Atoms are the smallest particle of an element that retains its
properties. Atoms contain…
Subatomic Particle
Location in Atom Charge Mass
Proton
Electron
Neutron
In nucleus
Outside nucleus, in energy levels
(clouds)
In nucleus
Positive
Negative
Neutral
Similar to the neutron
Very small compared to proton
99.9% of mass
Isotopes• Are a different form of the atom that
have the same number of protons in nucleus but a different number of neutrons.
• Their masses vary• Chemically behaves the same, may affect radioactivity
Ions• Are atoms that have lost or gained
electrons to become stable• Atoms that lose electrons are positively
charged ( # protons > # electrons)• Atoms that gain electrons are negatively
charge ( # protons < # electrons)
Using the Periodic Table and the information below, determine how many subatomic particles (protons, electron, and neutrons) are in…
a. 25Mg2+
b. Calcium – 40
c. 76Ge
Try your best!!!
25Mg 2+12
Mass number(must be provided)
Atomic number(on periodic table)
Charge= p + n
= p (also e if not charged)
= p - e
•Calcium - 40Mass number
Fill in please
Symbol # Protons # Electrons # Neutrons Charge
80Br
60Co2+
11 14 1+
7 10 15
Do Now…• Becky earned the following quiz grades… 87, 56, 94, 88 and 80. What is her quiz average?• Becky’s HW average was a 55 and her test average was a 75. Her teacher based her overall class grade on the following percentages: HW is 20%, Quiz is 50%, and Test is 30%. What is her overall grade in this class?
Standard: Carbon-12
• This isotope of carbon was assigned a mass of exactly 12 amu
• 1 amu (atomic mass unit) = 1/12 the mass of a carbon-12 atom
• Carbon-12 has 6 protons and 6 neutrons• The mass of the proton is about 1 amu• The mass of the neutron is about 1 amu
Since each isotope of given element has different masses, the atomic mass is an
average • Chlorine has two naturally occuring
isotopes. Chlorine-35 has a mass of 34.969 amu and chlorine-37 has a mass of 36.966 amu.
• Chlorine-35 has a natural abundance of 75.77% and chlrorine-37 has a natural abundance of 24.23.
• What is atomic mass of chlorine?