atoms what are we going to study about the atom? history structure properties forces

Atoms

What are we going to study about the atom?•History •Structure•Properties•Forces

Atomic Structure1. What is an atom composed of?

2. What subparticle(s) are responsible for an atom’s charge?

3. What subparticle(s) are responsible for an atom’s mass?

4. Illustrate an atom, identifying the subparticles and their location within the atom.

Atomic StructureSubatomic Particle

symbol charge Mass (g)

mass (amu)

proton p+ +1 1.674 x 10 -24 1

electron e- - 1 9.11 x 10-28 0

neutron n0 0 1.675 x 10 -24 1

Distinguishing Atoms1.Draw the atom below and identify the following:

electrons, protons, neutrons, electron cloud, nucleus, and energy levels.

2.What distinguishes one element’s atom from another element’s atom?

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What distinguishes each element below from one another?

Distinguishing Atoms

Distinguishing AtomsAtomic number • The number of protons within an atom’s nucleus.• An atom’s I.D.• Atoms of the same element always have the same

number of protons.

• What do you notice about the atomic numbers on the periodic table?

An Atom’s MassMass number : • The mass of a single atom.

• Sum of the p+ and n0 within an atom.

• Unit: atomic mass unit (amu)

• The mass number is NOT the same as Atomic Mass

Atomic StructureSubatomic Particle

symbol charge Mass (g)

mass (amu)

proton p+ +1 1.674 x 10 -24 1

electron e- - 1 9.11 x 10-28 0

neutron n0 0 1.675 x 10 -24 1

Element’s Subatomic Differences

Element AtomicSymbol

Atomic Number

Mass #(amu)

# of p+ # of n0 # of e-

Neutral Atoms• Most matter in nature is neutral. (Doesn’t shock us!)• This means the atoms making up the matter is

neutral. • What are the two charged subatomic particles? p+ and e-For an atom to be neutral the # of p+ = # of e-.

Elements QuizWhen: Thursday

What: First 20 elements on the periodic table.

Know: symbols and names

Atoms

What are we going to study about the atom?•History •Structure•Properties•Forces

Isotopes

What is an isotope?• Atoms of the same element that have different

number of neutrons.

• Also have different number of neutrons.

Common Isotopes of Carbon

C-12 C-13# of p+, n0, e-? # of p+, n0, e-?

Atomic Structure

History, Structure and Properties of the Atom

History of the Atom

•Great Thinkers (2,000yrs. Ago)

•Age of Reason and Thought

•Democritus vs. Aristotle view on the make-up of matter.

Democritus(400b.c.)Greek Philosopher

1) Observed matter to be made up of atoms.

2) Atoms are the smallest form of matter.

3. Atoms cannot be broken down.

3) The types of atoms in matter determine its properties.

Aristotle: Greek Philosopher (300b.c.)

• Aristotle observed matter to be made from four things:

air, earth, fire and water.

John Dalton’s Atomic Model

John Dalton’s Atomic Model

• English school teacher• Proved Democritus atoms

hypothesis using the scientific method.

• His conclusions produced:

Dalton’s Atomic Theory

1. Atoms are the building blocks of all matter.

1. Atoms cannot be subdivided.

2. Each element has the same kind of atoms.

3. In a compound, the different atoms chemically combine in the same way (fixed composition).

4. Atoms cannot be created or destroyed just rearranged.

Dalton’s Atomic Theory

Thomson’s Plum Pudding Model

Thomson’s Cathode Tube Experiment

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Subatomic Particle: ElectronJ.J. Thomson (pg. 105)• 1897 discovered electrons in gas atoms using a

cathode ray tube. • Determined electrons have a negative charge.• Electrons have the same charge in all atoms.

Robert Millikan: Determined the mass of the electron to be very tiny.

J. J Thomson’s Plum Pudding Model• If atoms are made of electrons how come most

matter does not shock us?• Atoms must have positive particles, too. • He proposed the Plum Pudding Atomic Model

• An atom is equally made up of positive and negative particles.

Goldstein’s Cathode Tube Experiment

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He discovered protons using a cathode ray tube. Observe particles moving in the opposite direction.

Subatomic Particles: Protons

• 1886 Eugen Goldstein observed particles traveling in the opposite direction of the cathode rays(electrons).

• He knew these particles must be (+) charged. They were called protons.

• Protons charge is the same for all atoms• Protons have a significant mass compared to

the electron.

Rutherford’s Model of the Atom

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Rutherford’s Gold Foil Experiment

Rutherford’s Conclusion

•Most of the atom is empty space.

•Small dense region composed of (+) charged particles.(Nucleus)

Rutherford’s Nuclear Atom Model

•What keeps the protons within the nucleus ?(Like particles repel each other)

•1932 - James Chadwick discovers that the nucleus also has neutral particles present. He called them neutrons.

Subatomic Particle: Neutron

Chadwick’s Experiments: Neutron

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Bohr’s Model of the Atom

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Bohr’s Model of the Atom

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Current Atomic Model

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Erwin Schrodinger

Current Atomic Model

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Erwin Schrodinger

Current Atomic Model

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Erwin Schrodinger

Types of electron paths around nucleus

Bell Ringer

1. Compare the different views Aristotle and Democritus had about what matter was made of.

2. Which Greek philosopher was correct ?3. Which later scientist proved his view?

Bell Ringer:4. a. Identify and explain this Atomic Model?

b. Who concluded this atomic model?

Bell Ringer5. Look at the following experiment below.a. What was this experiment called?b. Who developed this experiment?c. Did his experiment prove or disprove the

Plum Pudding Model?

Rutherford’s Conclusion

•Most of the atom was empty space.•Small dense region composed of (+) charged particles. (nuclues)

Rutherford’s Atomic Model

Rutherford’s Nuclear Atom Model

•What keeps the protons within the nucleus ?(Like particles repel each other)

•1932 - James Chadwick discovers the nucleus also has neutral particles present. He called them neutrons.

•Neutrons have a significant mass like protons.

Subatomic Particle: Neutron

Modern Atomic Model

Properties of Subatomic Particles Atomic Subparticles

Charge mass (g) mass (amu) subparticle’s contribution to atom

Electron (- charge) 9.11 x 10 -28

Proton (+ charge) 1.674 x10-24

Neutron (neutral) 1.675 x10-24

Neutral Atoms

Subatomic Masses (amu)

Subatomic Particle

symbol charge Mass (g) (g)

mass (amu)

proton P+ +1 1.674 x 10 -24 1

electron e- - 1 9.11 x 10-28 0

neutron n0 0 1.675 x 10 -24 1

Atom’s Subatomic Particles

Problem B: A cesium (Cs) atom has a mass of 133 amu and an atomic number of 55. How many p+, e-, and n0 are there?

Problem C: An iron atom has an atomic number of 26 and consists of 30 neutrons.

a. How many p+ and e- are there?b.What is iron’s mass number (amu)?

Atomic Subparticles

Isotopes

• Isotopes= atoms with different number of neutrons in their nucleus.

• Elements can have several isotopes.Ex. Carbon C-12 and C-14 (mass #)• Mass # changes. (varied # neutrons)• Atomic # stays the same (# of protons).

Element’s Isotopes• Oxygen has three isotopes. They are O-16, O-17, and O-18.1.What is the mass number for each isotope of

oxygen in amu?

2. What is the atomic number for each isotope of oxygen?

3. What is the number of p+, n0, and e- for each isotope of Oxygen ?

• Atomic mass= the weighted average mass of all the element’s isotopes present within a naturally occuring sample of matter.

• Calculate Atomic Mass of an Element 1. Multiply the mass # of each isotope by its

natural abundance ( common occurance) in decimal form.

2. Add all the isotopes products together.

Atomic MassElement’s average mass

Atomic Mass(Element’s average mass)

• Carbon (C) has two isotopes: Carbon-12 has a natural abundance = 98.89%Carbon-13 has a natural abundance = 1.11%Carbon’s atomic mass=(12 x 0.9889) + ( 13x0.0111) = 12.011 amu = 12 amu (2 sig. figures)

Atomic Mass Unit (amu)• Scientist needed an easier value to describe an

atom’s mass #.• Use a reference isotope as a standard.• Carbon-12 was chosen as the reference isotope

because of its natural abundance and strong stability.

• Carbon’s atomic mass unit = 12 amu• Atomic mass unit (amu)= 1/12 the mass of a

Carbon-12 atom. • Compare atom’s mass with Carbon

Periodic Table

• Atomic # = The elements are arranged in numerical order based on the number of protons present within their atom.

• Metal vs. Non-metal vs. Metalloids

• Periods vs. Groups

Periodic Table:Metals

• Metals are the majority of elements on the periodic table.

• They are every thing left of the metalloids. • Some metals are extremely reactive and some

don’t react easily. • Transition metals are elements that form a

bridge between the elements on the left and right sides of the periodic table.

Periodic Table: Non-metals

• Non-metals are elements that are poor conductors of heat and electric current.

• Because non metals have low boiling points, many non metals are gases at room temperature.

• Fun fact-All the gases in the periodic table are non metals

Periodic Table: Metalloids

• Metalloids are elements with properties that fall between those of metals and non-metals.

• Metals are good conductors of electric current and non-metals are poor conductors of electric current.

• Metalloids ability to conduct electric current varies with temperature.

• Examples of metalloids:– Boron, silicon, germanium, arsenic, antimony, polonium,

and astatine.

Periodic Table:Periods (rows)

Periodic Table:Groups

• Each column in the periodic table;;• The elements of the group have similar properties &

Electron configurations;;• The electron configuration determines its chemical

properties;;• Properties of elements repeat in a predictable way

when atomic numbers are used to arrange elements into groups;;

• The pattern of repeating properties is the periodic law;;

An Element’s Isotopes

• Isotopes= atoms with different number of neutrons in their nucleus.

• Elements can have several isotopes• Mass # changes. (varied # neutrons)• Atomic # stays the same (# of protons)• Chemical properties of an element’s

isotopes are the same because their # of protons and electrons are the same.

• Atomic mass= average mass of all the naturally occurring isotopes of an element.

• Multiply the mass number of each isotope by its natural abundance (decimal form) and then add all the isotopes products together.

Atomic MassElement’s average mass

Atomic Mass(Element’s average mass)

• Carbon (C) has two stable isotopes: Carbon-12 has a natural abundance = 98.89%Carbon-13 has a natural abundance = 1.11%Carbon’s atomic mass=(12 x 0.9889) +13x0.0111) = 12.011 amu

Bell Ringer: 9/9/09

• 1. What is an isotope?• 2. How many isotopes did Kandium have?• 3. Did each of Kandium’s isotope have the same

mass?• 4. What two values did you need to calculate

Kandium’s atomic mass?• 5. After you calculated Kandium’s atomic mass

what other value did you need to determine its atomic composition (p+,e-, n0)

Element’s Atomic Mass

• Element’s atomic mass = average mass calculated from its isotopes.

• Isotopes : mass # (amu) and relative abundance

Ex. Calculate Nitrogen’s atomic mass:Nitrogen-14 has a natural abundance 99.63%Nitrogen-15 has a natural abundance 0.37%

Calculating Kandium’s Atomic Mass

• M&M –• Reesium-• Skittlium-• Ka atomic mass=

Kandium Lab

• Realistically, we can determine an element’s isotopes mass(g) by using a mass spectrometer.

• Proton = 1.67x10^-24 g• Neutron =1.67x10^-24g• Electron = 9.11x10^-28g (very insignificant)

• Mass # in grams for an atom is important information but values are not easy to work with .

Atomic Mass Unit (amu)

• Compare atom’s mass with carbon.• Ex. If Helium has a mass of 4 amu how does it

compare with Carbons mass in amu? • Amu = 1/12 C, 4(1/12) = 1/3x mass of C• Ex. If Sulfur has a mass of 32 amu, how does it

compare with Carbon mass in amu.• Amu = 1/12 C 32/12 = 2.67x mass of C

Atom Composition

• If we know the atomic mass and the atomic number we can determine the atom’s composition : # of e-

• # of p+• # of n0

Atomic CompositionShorthand

• Shorthand method of atomic composition: Carbon-12 has an atomic # of 6

Ex. Oxygen-16 has an atomic # of 8

Ex. Silicon-28 has an atomic # of 14

Periodic Table

• The periodic table is arranged in numerical order by an atom’s atomic #.

• What is an atom’s atomic #?• Why are the elements arranged this way?Atom’s chemical nature is dependent upon its

charged particles :Atom’s protons remain conserved with most

reactions because present within nucleus. The # of electrons (electron cloud) will fluctuate with most reactions

Periodic Table Trends

• Organizing atoms based on atomic # establishes trends:

• Period= The horizontal rows within a periodic table. The atoms in each row share a pattern of properties.

• Group= The vertical columns of the periodic table. Atoms in each group share similar physical and chemical properties.

Bell Ringer(9/10/09)

1. How are elements arranged in the periodic table?2.What does period and group refer to on the

periodic table? 3. Identify which subparticles exist in the nucleus and

the electron cloud.4.Which two subparticles affect the chemical nature

of atoms?5.What subparticle determines the mass of the atom?6.Which subparticle is also the atomic #?

•What is the total # of atoms making up the Kandium sample? Record in table. •What is the total # of atoms making up the Kandium sample? Record in table.

Objectives

• I can determine the atomic composition of atoms when I know the atomic mass and atomic #.

• I can recognize that the periodic table is organized by an element’s atomic number.

• I can divide the elements in the periodic table into periods and groups.

• I can identify and distinguish between metals, nonmetals, and metalloids on the periodic table.

• I can determine if an atom is neutral or has an overall charge based on the # of electrons present within the atom.

Periodic Table Trends

• Organizing atoms based on atomic # establishes trends:

• Period= The horizontal rows within a periodic table. The atoms in each row share a pattern of properties.

• Group= The vertical columns of the periodic table. Atoms in each group share similar physical and chemical properties.

Periodic Table

Elements can be classified into 3 groups:I. Metals= good conductors of electricity and heat.

II.Non-metals= primary make-up of life. Synthetic (man-made) materials.Poor conductors of electricity and heat.

III Metalloids = properties of metals and non-metals.

Neutral Atom

• What are the two charged subatomic particles that make-up an atom?

• Neutral atoms: # protons = # of electrons

• What happens if they are not balanced?

Charged Atom

Atoms become charged when they gain or loose electrons. This would affect the atom’s balance between # of p+ and # of e-.

• Charged atoms are called ions.

Ion Types

• Ions = charged atoms• Two types of Ions 1. Anion= An atom that has gained one or more

electrons. What charge would an anion have?• Non-metal ions can be anions.Ex. What are some examples of anions?

Anions

Ex. Fluorine (F) atomic # = 9Neutral Fluorine: F

Anion

Ex. Phosphorous (P) atomic # is 15.Neutral Phosphorous:P

Ion Types

• Cations= An atom that looses one or more electrons.

What charge would a cation have?

• Metals can be cations.What are some examples of cations?

Cation

• Ex. Potassium (K) atomic # = 19• Neutral Potassium: K

Cation

• Ex. Iron (Fe) atomic # = 26Neutral Iron: Fe

Mass # vs. Atomic Mass

• Mass # = # of protons and # of neutrons in an atom.

• Atomic Mass = The average mass for an element. It is determined by taking in account all the isotopes that make-up an element. You must know the isotopes relative abundance and mass # to calculate the atomic mass of the element.

-Atomic mass = observed on the periodic table.

Atoms : To be neutral or charged

• Neutral atom = # p+ is equal to # e-• Ions (charged atoms) = change in # of e- a. Cation (+ charge) = # of e- is less than in the

neutral atom. Ex. Metals (Na +) # of e- = subtracting the charge from # of p+

b. Anion = # of e- are more than in the neutral atom. Ex. Nonmetals. (F-)

# of e- = adding the charge to # of p+

Neutral or Not

1. Beryllium : Be 2+

2. Sulfur: S

3. Sulfur: S 2-

d) the larger the atom the weaker the strong force is --> larger atoms tend to decay (nuclear decay)

e) also, atoms with certain numbers of protons tend to decay--if they have the same number of protons and neutrons they tend to be more stable--different numbers--more unstable

5) 4 forces in nature a) strong force b) weak force c) electrical force d) gravitational force6) Usages of Nuclear Chemistry a) production of power b) killing bacteria in food products c) medicine -cancer treatments along with

other usages

7) Radiation-Radioactivity a) radiation is electrically charged particles or

waves emitted by an energy source or decaying atoms.

b) radioactivity - is radiation from an unstable atom that is splitting or undergoing decay. There are three types of radioactive materials

* Alpha radiation - harmful if inhaled or otherwise enter the body - can be stopped by clothes, skin or a sheet of paper.

Some producers of alpha particles are among the longest lasting waves

* beta particles - more penetrating power than alpha but most serious when inhaled or ingested -- tend to concentrate in certain body parts, such as bone -can cause serious health problems with minimal exposure

* gamma radiation-- highest energy levels -similar to x-rays, can penetrate the body and cause direct damage to internal organs

Types of Radiation• 1. Alpha Radiation : an alpha particle emitted from radioactive

nuclei, consists of 2 protons and 2 neutrons, but no electrons• Not very harmful• Large atoms are not very stable and need to decrease mass• What is the charge and mass of an alpha particle?• +2 and 4amu• Example• 226

88Ra → 22286Rn + 4

2He• Radium Radon Alpha Particle

Types of Radiation• Beta Radiation: fast moving electron emitted from a

radioactive element called a Beta Particle.• Can cause serious health problems especially in bones• Atoms want to have a 1 : 1 neutron to proton ratio• Beta emission is used to decrease the neutron to proton ratio.• What is the charge and mass on a beta particle?• -1 and 0• 14

6C → 147N + 0

-1β

Types of Radiation

• Gamma Radiation: Gamma rays are released from radioactive nuclei.

• Gamma rays have no mass or charge.• Gamma rays are very harmful and have a very

high energy

* Effects of radioactive particles on biological systems --can alter cellular function particularly DNA--carries the cells genetic code-causing birth defects-can create mutated forms of cells that can cause cancerous growths

8) Fusion-Fission a) fusion uniting of nuclei of two light elements

to form heavier nucleus- example sun--

b) fission - a heavy nuclide splits into two or more intermediate- sized fragments when hit in a particular way by a neutron --utilized by nuclear power plants --to make nuclear bombs

Periodic Table Trends

• Organizing atoms based on atomic # establishes trends:

• Period= The horizontal rows within a periodic table. The atoms in each row share a pattern of properties.

• Group= The vertical columns of the periodic table. Atoms in each group share similar physical and chemical properties.

Elements in a Period (row)

• The mass of an atom increases as you go from left to right across any period.

Metals, Non-metals, and Metalloids

• Metals= shiny, good conductors of electricity and heat, malleable, and ductile.

(primarily solids)• Non-metals = poor conductors of electricity,

sometimes transparent, neither malleable nor ductile, brittle.

(solids, liquids and gases)Metalloids= Weak conductors of electricity, useful

semi-conductors. They can exhibit metal and nonmetal properties.

Postulate 4 is actually the Law of Definite Proportions

, by Joseph Louis Proust in 1797.

a) a given chemical compound always contains the same proportion by mass of its constituent elements or...

b) the relative amount of each element in a particular compound is always the same, regardless of preparation or source.

Assignment: Illustrate the following Atomic Models

•Dalton’s Atomic Model•Thomson’s Plum Pudding Model• Rutherford’s Nuclear Model• Modern Atomic Model.

Thomson’s Plum Pudding Model