Unit 1Unit 1Ch#1-3Ch#1-3

Atomic StructureAtomic Structure

►Spelling Terms (25 terms)Spelling Terms (25 terms)

AtomsAtoms ProtonsProtons ElectronsElectrons

NeutronsNeutrons SubatomicSubatomic NucleusNucleus

NucleiNuclei NanotechnologyNanotechnology

IndivisibleIndivisible Atomic Mass Unit (AMU)Atomic Mass Unit (AMU)

IsotopeIsotope NuclearNuclear EndothermicEndothermic

Ernest RutherfordErnest Rutherford Erwin SchrErwin Schrőődingerdinger

John DaltonJohn Dalton Neils Bohr Joseph ThomsonNeils Bohr Joseph Thomson

Hypothesis Hypothesis ExothermicExothermic AnodeAnode

AnalyticalAnalytical AbundanceAbundance CathodeCathode

PrecipitatePrecipitate Analyze dataAnalyze data ConclusionConclusion

I. Atoms I. Atoms

A.A. AtomAtom- the smallest particle of an element that - the smallest particle of an element that RETAINSRETAINS the properties of that element. the properties of that element.

1.1. The word Atom comes from the Greek word The word Atom comes from the Greek word “Atomos” = indivisible or Uncut able“Atomos” = indivisible or Uncut able

2.2. Are they INDIVISIBLE? Are they INDIVISIBLE?

3.3. NanotechnologyNanotechnology- We can isolate a single atom and - We can isolate a single atom and cause it to have different properties depending on cause it to have different properties depending on how we arrange them.how we arrange them.

B.B. The idea of atoms was 1The idea of atoms was 1stst suggested by suggested by Democritus, an ancient Greek, 400 B.C.Democritus, an ancient Greek, 400 B.C.

1. 1. Ideas NOT useful -NO Exp. evidenceIdeas NOT useful -NO Exp. evidence..

C.C. Late 1700’s English Chemist & Physicist, Late 1700’s English Chemist & Physicist, John Dalton (1766-1844) stated his atomic John Dalton (1766-1844) stated his atomic theory:theory:

1.1. All elements are composed of tiny, indivisible All elements are composed of tiny, indivisible atoms.atoms.

2.2. Atoms of same element are identical and they Atoms of same element are identical and they differ from any atom of any OTHER element.differ from any atom of any OTHER element.

a)a) I.O.W.- An element is composed of many atoms that I.O.W.- An element is composed of many atoms that behave alike behave alike

b)b) Analogy- Groups of cells = TissuesAnalogy- Groups of cells = Tissues

Groups of Atoms = ElementsGroups of Atoms = Elements

3.3. Atoms of DIFFERENT elements can combine w/ Atoms of DIFFERENT elements can combine w/ one another in simple, WHOLE # ratios to form one another in simple, WHOLE # ratios to form compounds. (based on mass)compounds. (based on mass)

a)a) A.k.a. “Law of Definite Proportions”A.k.a. “Law of Definite Proportions”

b)b) A + B = CA + B = C

5g 2g 7g 5:25g 2g 7g 5:2

A + B = DA + B = D

10g 2g 12g 10:210g 2g 12g 10:2

4.4. Chem Rxn’s occur when atoms are separated, Chem Rxn’s occur when atoms are separated, joined, or rearranged.joined, or rearranged.

II. Electrons, Protons & NeutronsII. Electrons, Protons & NeutronsA.A. Most of John Dalton’s theory is still accepted but 1- Most of John Dalton’s theory is still accepted but 1-

atoms ARE divisible!atoms ARE divisible!B.B. With increasing technology dozens of subatomic With increasing technology dozens of subatomic

particles have been discovered and NO single theory particles have been discovered and NO single theory can account for all of them.can account for all of them.

C.C. We are concerned with 3: Electrons, Protons, and We are concerned with 3: Electrons, Protons, and Neutrons.Neutrons.

1.1. Electrons (eElectrons (e--) Negatively charged subatomic particle that is ) Negatively charged subatomic particle that is located in an electron cloud around nucleus.located in an electron cloud around nucleus.

a)a) Discovered by scientists interested in electricity not chem Discovered by scientists interested in electricity not chem in 1897 (JJ Thomson).in 1897 (JJ Thomson).i.i. Studied electric current through gases in a closed glass Studied electric current through gases in a closed glass

tube with metal disks called electrodes at each end.tube with metal disks called electrodes at each end.

ii.ii. Electrons travel as a ray of light from cathode (+) to Electrons travel as a ray of light from cathode (+) to anode (-).anode (-).

Ex: Older television tubes, light bulbs, etcEx: Older television tubes, light bulbs, etc

2. 2. Proton (pProton (p++)) - positively charged subatomic particle - positively charged subatomic particle

a)a) Located in nucleus and allows atom to be electrically Located in nucleus and allows atom to be electrically

neutral b/c number of pneutral b/c number of p++ = e = e- - = 0.= 0.

b)b) 1840 times heavier than e1840 times heavier than e--..

3. 3. Neutron (nNeutron (noo)) – – subatomic particle with NO charge, subatomic particle with NO charge, discovered in 1932.discovered in 1932.

a)a) located in the nucleus with proton and has a mass located in the nucleus with proton and has a mass nearly equal to that of a protonnearly equal to that of a proton..

ParticleParticle SymbolSymbol Relative Relative ChargeCharge

~ Mass~ Mass

(amu)(amu)**

locationlocation Actual mass Actual mass (g)(g)

ElectronElectron ee-- 1-1- 1/18401/1840 Moves Moves around around nucleusnucleus

9.11 x 109.11 x 10-28-28

ProtonProton pp++ 1+1+ 11 In In nucleusnucleus

1.67 x 101.67 x 10-24-24

NeutronNeutron nnoo 00 11 In In nucleusnucleus

1.67 x 101.67 x 10-24-24

Table 1: Properties of Subatomic Particles

* 1 amu = 1.66 x 10-24 g

III. Structure of AtomIII. Structure of AtomA.A. NucleusNucleus- has a positive charge b/c it is composed of - has a positive charge b/c it is composed of

(p(p++ + n + noo) – located in center of every atom-very small part of the ) – located in center of every atom-very small part of the vol. of atom.vol. of atom.

B.B. Electron cloudElectron cloud – negatively charged b/c comprised of e – negatively charged b/c comprised of e--..

IV.IV. Development of Atomic Development of Atomic ModelsModels

A.A. John Dalton John Dalton (1766-1844) wrote his atomic (1766-1844) wrote his atomic theory which was a great advance in explaining theory which was a great advance in explaining the nature of chem. Rxns.the nature of chem. Rxns.

B.B. Joseph John Thomson Joseph John Thomson (1856-1940) discovered (1856-1940) discovered the electron and proposed a model referred to the electron and proposed a model referred to as the “plum pudding atom” (1910-as the “plum pudding atom” (1910-Lord Kelvin Lord Kelvin aka William Thomsonaka William Thomson) negative e) negative e-- (raisins) stuck (raisins) stuck into a lump of + protons (dough)into a lump of + protons (dough)

C.C. In 1911, Ernest Rutherford (1871-1937) decided to In 1911, Ernest Rutherford (1871-1937) decided to test prevailing theory of atomic structure(ptest prevailing theory of atomic structure(p++ and e and e-- are evenly distributed) in order to define a more are evenly distributed) in order to define a more refined picture of an atom.refined picture of an atom.

1.1. Used alpha particles which are positively charged He Used alpha particles which are positively charged He atomsatoms

2.2. HypothesisHypothesis: alpha particles would pass thru gold foil : alpha particles would pass thru gold foil easilyeasily

3.3. ResultsResults:1/20,000 were repelled back or 1/8000 were :1/20,000 were repelled back or 1/8000 were deflected to the side.deflected to the side.

4.4. ConclusionConclusion: atoms have a positive center called a : atoms have a positive center called a nucleus b/c protons are located there and likes repel each nucleus b/c protons are located there and likes repel each other. Whereas, the majority of the vol. of an atom is other. Whereas, the majority of the vol. of an atom is empty space where the negative eempty space where the negative e-- are located and the are located and the HeHe++ passed thru unhindered b/c opposites attract. passed thru unhindered b/c opposites attract.

Rutherford’sRutherford’sGold-Leaf Gold-Leaf ExperimentExperiment

Conclusions:Conclusions:

Atom is mostly empty spaceAtom is mostly empty space

Nucleus has (+) chargeNucleus has (+) charge

Electrons float around nucleusElectrons float around nucleus

D.D. In 1913 Niels Bohr, a student of Rutherford’s, In 1913 Niels Bohr, a student of Rutherford’s, came up with a new model aka Bohr Model. came up with a new model aka Bohr Model. Proposed that e- are arranged in concentric Proposed that e- are arranged in concentric circular paths or orbits around the nucleus aka circular paths or orbits around the nucleus aka planetary model.planetary model.

V. Atomic Number V. Atomic Number

A.A. The atoms of one element differ from the atoms of The atoms of one element differ from the atoms of another element b/c their nuclei contain different another element b/c their nuclei contain different number of protons.number of protons.

B.B. Call this the “Atomic Number”Call this the “Atomic Number”

C.C. On periodic table- On periodic table- Whole #Whole # - - ↑↑ from L to Rfrom L to R

D.D. Atoms are electrically neutral so pAtoms are electrically neutral so p++ = e = e- - !!!!Ex: Atomic # = 11Ex: Atomic # = 11

= Na = Na & e& e-- ? p ? p++? ? → 11→ 11

VI. Mass Number VI. Mass Number

A.A. DefinitionDefinition – Total # of p – Total # of p++ and n and noo in the nucleus. in the nucleus.

- - Decimal number rounded to nearest whole number.Decimal number rounded to nearest whole number.

Si

14

28.086

Silicon

Atomic #

Symbol

Name

Atomic Mass Number

B.B. PurposePurpose- To find the number of neutrons in an - To find the number of neutrons in an atom.atom.

Ex. Beryllium ( )Ex. Beryllium ( )

Mass # = Mass # = 9 9

Atomic # = 4 (subtract)Atomic # = 4 (subtract)

# of n# of noo = = 55

C.C. Examples!Examples!

Atomic Atomic ##

Mass #Mass # # of p# of p++ # of n# of noo # of e# of e-- SymbolSymbol

77 77

99 1010

3939 1919

5959 2727

# p+: 17

# no : 18

D.D. Bohr Model: nucleus + electron orbitals or Bohr Model: nucleus + electron orbitals or shellsshells--Named after Danish physicist-Neils Bohr (1885-Named after Danish physicist-Neils Bohr (1885-1962)1962)

2e

8e

18e

32e

n1 = 2

n2 = 8

n3 = 18

n4 = 32

H.W:Create A Bohr Diagram For the H.W:Create A Bohr Diagram For the Following ElementsFollowing Elements

1.1. BeBe

2.2. CC

3.3. NeNe

4.4. AlAl

5.5. CsCs

6.6. AsAs

E.E. Nuclear Symbols: Another way to Nuclear Symbols: Another way to illustrate composition of an elementillustrate composition of an element

XMass # A

Atomic # Z

Ex.

Ne Be

PracticePractice: Write a Nuclear : Write a Nuclear Symbol for the following Symbol for the following elements (HW:Notebook paper)elements (HW:Notebook paper)1.1. NN

2.2. ClCl

3.3. CaCa

4.4. AlAl

5.5. NaNa

6.6. GeGe

E.E. IsotopesIsotopes::

A.A. We know that an element cannot gain or lose protons We know that an element cannot gain or lose protons because the element because the element will become a different elementwill become a different element..

B.B. An element can gain or lose neutrons and not be An element can gain or lose neutrons and not be chemically altered. In other words, it will remain the chemically altered. In other words, it will remain the same element, however by adding or taking away same element, however by adding or taking away neutrons, the element’s mass will change accordingly.neutrons, the element’s mass will change accordingly.

C.C. This accounts for the fact that all element’s mass is This accounts for the fact that all element’s mass is given as a decimal (given as a decimal (average of all isotopesaverage of all isotopes).).

D.D. To symbolize: we also use To symbolize: we also use “ Nuclear Symbols” & “ Nuclear Symbols” & hyphenated names.hyphenated names.

He

4

2Atomic #

Mass #

Or Helium - 4

F.F. Examples: How many neutrons are in Examples: How many neutrons are in the following atoms? Isotope?the following atoms? Isotope?

a)a) 1818 O O b)b) 32 32 SS

c) c) 108108 Ag Ag d) d) 8080 Br Br

e)e) Two isotopes of oxygen are oxygen-16 & Two isotopes of oxygen are oxygen-16 & oxygen-18. Write the nuclear symbol for oxygen-18. Write the nuclear symbol for each.each.

16

47 35

8

VI. Atomic MassVI. Atomic Mass

A.A. Remember the mass of a proton & neutron are Remember the mass of a proton & neutron are 1 amu respectively.1 amu respectively.

B.B. Atomic massAtomic mass- is the weighted average of the - is the weighted average of the masses of the isotopes of that element.masses of the isotopes of that element.

C.C. A A weighted averageweighted average reflects both the mass & reflects both the mass & relative abundance of isotopes as they occur in relative abundance of isotopes as they occur in nature.nature.

D.D. How is the atomic mass of an element How is the atomic mass of an element calculated?calculated?

1.1. Isotope EquationIsotope Equation::55A (% abundance)A (% abundance)66A (% abundance) where A is any elementA (% abundance) where A is any element

5 amu x % abundance = Y5 amu x % abundance = Y

6 amu x % abundance = Z6 amu x % abundance = Z

Total = Y+Z = Ave. atomic massTotal = Y+Z = Ave. atomic mass

Ex: Element X has 2 natural isotopes. The isotope with a mass # of Ex: Element X has 2 natural isotopes. The isotope with a mass # of 10 has a relative abundance of 20%. The isotope with a mass 10 has a relative abundance of 20%. The isotope with a mass # of 11 has a relative abundance of 80%. Estimate the # of 11 has a relative abundance of 80%. Estimate the average atomic mass and determine its true identity and average atomic mass and determine its true identity and atomic #.atomic #.

Solution:Solution:

1010X & X & 1111XX

10 amu x 0.20 = 2.0 amu10 amu x 0.20 = 2.0 amu

11 amu x 0.80 = 11 amu x 0.80 = 8.8 amu +8.8 amu +

10.8 amu10.8 amu

Element is Boron (B), Atomic # 5Element is Boron (B), Atomic # 5

2. 2. Examples:Examples:

1) 99.985% 1) 99.985% 11H ; 0.015% H ; 0.015% 22H.H.

2) 99.76% 2) 99.76% 1616O; 0.04% O; 0.04% 1717O; 0.20% O; 0.20% 1818O.O.

Please Add to back of Review Please Add to back of Review Sheet:Sheet:

--Study Atomic Study Atomic Theory (4 parts)Theory (4 parts)

1.1.Write Nuclear Symbols for: Write Nuclear Symbols for: Li, Si, Ni, ILi, Si, Ni, I

2.2.Draw Bohr Models for: Draw Bohr Models for: K, Mn, Kr, HK, Mn, Kr, H

Review Game ?’sReview Game ?’s

1.1. Nuclear symbolsNuclear symbolsAuAu AgAg HH HeHe

1.1. 99.76% 99.76% 208208Bi; 0.04% Bi; 0.04% 209209Bi; 0.20% Bi; 0.20% 210210Bi.Bi.

2.2. Give an example of 2 ways to Write Give an example of 2 ways to Write the composition of an element: Use the composition of an element: Use same element in both!same element in both!