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?