CHEMISTRY CATALYSTS

Fall 2011 – Week 5 (Atomic Structure)

Catalyst (5 min) 9/6/11 Developing Atomic Models EQ: How has mankind’s view of the

atom changed over time?

1. Name the three subatomic particles that make up the atom.

2. Describe the properties and location of each part.

3. Draw an atom of Oxygen-17.

How can we know that these incredibly small, invisible

particles exist?

Atomic Theory

Early Atomic Theory

Empedocles (470 BC) All matter is composed of earth, air, water

and fire Democritus (440 BC)

Nature consists solely of an infinite number of indivisible particles called atomos (Greek for ‘cannot cut’)

Aristotle (250 BC) All matter is composed of earth, air, water

and fire, and this matter can be cut in half an infinite number of times

This atomic theory prevailed for 2000 years

Early Atomic Theory

John Dalton (1803-1810)

1. Elements consist of tiny particles called atoms.

2. Atoms of the same element are alike in mass and size.

3. Atoms combine to form compounds in simple numerical ratios, such as 1:2, 2:3, etc.

4. Atoms of two elements may combine in different ratios to form more than one compound. (Ex: H2O and H2O2)

Early Atomic Theory

Consequences of Dalton’s Law The Law of conservation of Mass/Matter:

“There is no detectable change in mass in an ordinary chemical reaction.”

The Law of Constant Composition:“A compound always contains the same

elements in the same proportions by mass.”

The Law of Multiple Proportions:

“The masses of one element that combine with a fixed mass of the second element are in a ratio of small whole numbers.”

Joseph John Thomson (1856-1940) Discovered the first subatomic particle,

the electron, in1897 using a cathode ray The cathode ray was actually a stream of

negatively charged electrons

The Plum Pudding Model

J.J. Thomson’s model of the Atom

positive negative

Ernest Rutherford (1871 – 1937) Discovered the nucleus in 1913 Only a few of the 8000 positively charged particles

shot at the gold foil were deflected or bounced back The Gold Foil experiment showed that the nucleus

was small, dense and positively charged

Rutherford went on to discover the proton in 1920 and James Chadwick discovered the neutron is 1932

Rutherford’s Gold Foil Experiment

Rutherford Gold Foil Experiment

http://www.youtube.com/watch?v=Q8RuO2ekNGw

The Nuclear Atom

Ernest Rutherford’s model of the atom

positive negative

Niels Bohr (1885 – 1962)

1913 – Bohr said that the characteristic color of elements could not be explained by earlier models

Bohr studied the energy levels of Hydrogen and determined that its electron travels on distinct paths like planetary orbits around the sun.

Flame Tests

potassium lithium strontium calcium sodium

Each element has a characteristic color when energy is added.

Planetary Model

Niels Bohr’s model of the atom

positive negative

Notes: Subatomic Particles

Particle

Charge

Location within atom

Relative Size (amu)

Mass (kg)

Proton +1 Nucleus 1 1.673 x 10-27

Neutron

0 (neutral)

Nucleus 1 1.675 x 10-27

Electron

-1Outside Nucleus

1/1840 ≈ 0 9.11 x 10-31

amu = atomic mass unit

Copy this table into your notes.TextbookPg 97

Catalyst (5 min) 9/7/11 Protons, Neutrons, &

Electrons EQ: How do you determine the number

of protons, neutrons, & electrons in atoms?

1. Draw this atom.2. Label its parts.3. What element is this?

Vocabulary

Atomic Number Number of protons in an atom

of an element Equals number of electrons in

neutral atoms Determines the order of elements

in the periodic table

3

Lilithium

6.9

3

Lilithium

6.9

Practice with Atomic #How many protons does an atom of chlorine (Cl) have?

How many protons does an atom of potassium (K) have?

How many electrons does an atom of (C) have?

Which atom has more protons, fluorine (F) or neon (Ne)?

17

19

6

Neon

Vocabulary

Isotope An atom of an element with a different

mass from another atom of the same element

The difference in mass must come from a different number of neutrons because the protons and electrons are the same.

Vocabulary

Mass Number The sum of all the particles in the

nucleus of an individual atom

protons + neutrons The actual mass of an individual atom This number does NOT appear on the

periodic table and is usually not equal to the average atomic mass of the element

Ways to Express Isotopes

Lithium - 7 Mass Number

Hyphen Notation

Li73

Atomic Number

Nuclear Symbol

Ways to Express Isotopes

Li - 7 Mass Number

Hyphen Notation

Li7

Nuclear Symbol

Calculating Neutrons in Isotopes

Lithium-6

Lithium-7

Atomic number of lithium = 3. Both have 3 protons

Mass number - protons = neutrons. For Lithium-6, subtract 6-3 to get 3 neutrons

For Lithium-7, subtract 7-3 to get 4 neutrons

Mass Numbers

Practice with Mass #

How many protons and neutrons are there in an atom of carbon-13?

How many protons and neutrons are there in an atom of ?

How many protons and neutrons are there in an atom of oxygen-18?

6 protons, 7 neutrons

6 protons, 8 neutrons

8 protons, 10 neutrons

C146

, 6 electrons

, 6 electrons

, 8 electrons

Practice

Combine this with Bohr’s Planetary Model of the Atom

Nitrogen-15 7 protons 7 electrons 8 neutrons

7 p+

8 n0

Vocabulary Review

Atomic number is… the # of protons found at the top of the periodic table square equal to # of electrons for neutral atoms

Mass number is… the # of protons plus the # of neutrons not on the periodic table (must be given)

Isotopes are… the same element with different # of neutrons the same element with different mass

numbers

Lithium - 7

Li73

Catalyst (5 min) 9/8/11 Isotopes EQ: What are isotopes?

Identify the number of protons, neutrons, and electrons in…

Uranium-235 O-17 Pb

C

20782

13

Vocabulary Review

Atomic number is… the # of protons found at the top of the periodic table square equal to # of electrons for neutral atoms

Mass number is… the # of protons plus the # of neutrons not on the periodic table (must be given)

Isotopes are… the same element with different # of neutrons the same element with different mass

numbers

Li73

Lithium - 7

Vocabulary

AverageAtomic Mass The weighted average of the masses

of all the atoms of an element The periodic table is NOT ordered by

atomic masses. For example, check out Co and Ni.

More on average atomic mass tomorrow...

3

Lilithium

6.9

3

Lilithium

6.9

PracticeWhat is the atomic mass of chlorine?

What is the atomic mass of carbon?

Which element has greater atomic mass, potassium or argon?

35.4 amu

12.0 amu

argon

Draw a concept map for the following terms:

The details are the most important part! Don’t forget to include them!

Classwork 9/8/11

Matter Atom Element Isotope Proton

Neutron Electron Atomic number Atomic mass Mass number

This concept map was made

using Cmap Tools, a free

software download available

online. Try it out!

This concept map was made

using Cmap Tools, a free

software download available

online. Try it out!

Matter Atom Element Isotope Proton Neutron

Electron Atomic

number Atomic

mass Mass

number

Concept Map

Note the connections between words

Yours may look different from this one!

9/9/11 Atomic Models EQ: How can I model the parts of an atom?

1. Count the protons, neutrons, & electrons in these pictures.

2. Name the isotopes using hyphen notation and the nuclear symbol formats.

Catalyst (5 min)Li

73

Lithium - 7