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8/8/2019 Atoms Ppt OriG
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ATOM
MR.JUSTIN SAMSON
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HISTORY OF THE ATOMHISTORY OF THE ATOM
460 BC Democritus develops the idea of atoms
he pounded up materials in his pestle
and mortar until he had reduced them
to smaller and smaller particles which
he called
ATOMAATOMA
(greek for indivisible)
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HISTORY OF THE ATOMHISTORY OF THE ATOM
1910Ernest Rutherford
oversaw Geiger and Marsden
carrying out his famous experiment.
they fired Helium nuclei at a piece
of gold foil which was only a few
atoms thick.
they found that although most of
them passed through. About 1 in
10 000 hit
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HISTORY OF THE ATOMHISTORY OF THE ATOM
gold foil
helium nuclei
They found that while most of the helium nuclei passed
through the foil, a small number were deflected and, to
their surprise, some helium nuclei bounced straight back.
helium nuclei
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ATOM
The atom is a basic unit ofmatterthat consists ofa dense, central nucleus surrounded by a cloud ofnegatively charged electrons.
The atomic nucleus contains a mix of positivelycharged protons and electrically neutral neutrons.
The electrons are arranged in orbits or shellscalled K,L,M starting from the orbital closest to thenucleus.
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atoms
The electrons of an atom are bound to the nucleus by theelectromagnetic force. Likewise, a group of atoms canremain bound to each other, forming a molecule
An atom containing an equal number of protons andelectrons is electrically neutral, otherwise it has a positive
or negative charge and is an ion. An atom is classified according to the number of protons
and neutrons in its nucleus: the number of protonsdetermines the chemical element, and the number ofneutrons determines the isotope of the element.[1]
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Nucleus: The nucleus is the very dense regionconsisting of nucleons (protons and neutrons) atthe center of an atom. Almost all of the mass in an
atom is made up from the protons and neutrons inthe nucleus,.
Electron orbit - the path of an electron around the
nucleus of an atom
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An atom consists of aAn atom consists of a nucleusnucleus
(of(ofprotonsprotons andand neutronsneutrons))
electronselectrons in space about the nucleus.in space about the nucleus.
The AtomThe Atom
NucleusNucleus
Electron cloudElectron cloud
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ATOMATOMCOMPOSITIONCOMPOSITION
protons and neutrons inprotons and neutrons inthe nucleus.the nucleus.
the number of electrons is equal tothe number of electrons is equal to
the number of protons.the number of protons.
electrons in space around theelectrons in space around the
nucleus.nucleus.
The atom is mostlyThe atom is mostly
empty spaceempty space
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ATOMIC COMPOSITIONATOMIC COMPOSITION
Protons (pProtons (p++)) + electrical charge+ electrical charge
mass = 1.672623 x 10mass = 1.672623 x 10--2424 gg
relative mass = 1.007 atomicrelative mass = 1.007 atomic
mass units (amu)mass units (amu) but we can round to 1but we can round to 1
Electrons (eElectrons (e--))
negative electrical chargenegative electrical charge
relative mass = 0.0005 amurelative mass = 0.0005 amu
but we can round to 0but we can round to 0
Neutrons (nNeutrons (noo))
no electrical chargeno electrical charge
mass = 1.009 amumass = 1.009 amu but we can round to 1but we can round to 1
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What is AMU?
An atomic mass unit (symbolized AMU or amu) isdefined as precisely 1/12 the mass of an atom
In imprecise terms, one AMU is the average of theproton mass and the neutron mass
The mass of an atom in AMU is roughly equal tothe sum of the number of protons and neutrons inthe nucleus
The AMU is used to express the relative masses of,various isotopes of elements. example, uranium-235 (U-235) has an AMU of approximately 235,while uranium-238 (U-238) is slightly moremassive.
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Properties of Atoms
Atomic Number- The number of protons in
the nucleus of a specific type of atom. Mass Number- The number ofprotons plus
neutrons in the nucleus of a specific type ofatom. Also referred to as atomic mass.
To figure out the number of neutrons in anatom, subtract the atomic number from themass number.
Example: Carbon has an atomic # of 6 and a massnumber of 12. This means carbon has 6 protons(A #) and 6 neutrons (M # - A #)
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Atomic Number, ZAtomic Number, ZAll atoms of the same elementAll atoms of the same element
have the same number ofhave the same number of
protons in the nucleus,protons in the nucleus, ZZ
1313
AlAl
Atomic numberAtomic number
Atom symbolAtom symbol
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Mass Number, AMass Number, A C atom with 6 protons and 6 neutrons is theC atom with 6 protons and 6 neutrons is the
mass standardmass standard
= 12 atomic mass units= 12 atomic mass units
Mass NumberMass Number(A)(A) = #= #protons + # neutronsprotons + # neutrons
A boron atom can haveA boron atom can have AA= 5 p + 5 n = 10= 5 p + 5 n = 10 amuamu
A
Z
10
5B
A
Z
10
5B
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Just What Size Is an Atom?
0.00013 micron
Atoms !!!
C
H
O
N
He
Na
Cl
Ca
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How Many Atoms Are In A Person?
thats eight million-million-
million-million-
thousand atoms
Wow!
Around 8,000,000,000,000,000,000,000,000,000
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HELIUM ATOM
+N
N
+-
-
proton
electron neutron
Shell
What do these particles consist of?
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quarks the protons and neutrons are made up of various
varieties of particles called quarks A set ofthree quarks makes up the proton and
another set of three makes up the neutrons. Eachquark carries a charge of 1/3rd of a proton.
The electron is still considered to be monolithicand is grouped under particles called leptons.
Binding energy: energy contained in holding theprotons and neutrons together in the nucleus of anatom or holding the atoms together in a molecule.
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Excitation & Ionisation
An electron revolving in a stationary orbit of an atom
absorbs some energy the electron may jump overto anorbit of higher energy. This process is called excitation
If the energy supplied is large enough to remove anelectron from the atom, then the atom is said to be ionized.The minimum energy needed to ionize an atom is called
Ionisation energy
characteristic x-ray: an x-ray that is emitted from an atomwhen an electron is displaced from an inner shell.
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Molecules are very small objects that are
made up of connected atoms
What are Molecules?
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Bohr Models Niehls Bohr
Discovered that electrons occupy different types oforbitals called energy levels. (much like the planetsaround the sun)
1stenergy level = 2
electrons
2ndenergy level = 8
electrons
3rdenergy level = 8
electrons
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AAMOLECULEMOLECULEis the smallest unit of ais the smallest unit of acompound that retains the chemicalcompound that retains the chemical
characteristics of the compound.characteristics of the compound.
Composition of molecules is given by aComposition of molecules is given by a
MOLECULAR FORMULAMOLECULAR FORMULA
HH22OO
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What Do Molecules Look Like?
Molecules can take on all kinds of
different shapes and sizes
Lets look at a few!
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Do Molecules Move?
Yes, they sure do!
How do they move?
It depends on whether they
are in a solid, liquid, or gas
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VALENCY BOND
The ability of one atom to join with another is calledvalency and the electron linkage between the atoms iscalled the valency bond.
There are 2 types of valency bond
1.ionic bond-this type of bond is created when one or more
electrons are transferred from one atom to another, formingcharged atoms(ions)
2.covalent bonds-this is formed by sharing of electrons
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Terms used to describe a nucleus
Nucleon- a proton or neutron within a nucleus Atomic no Z-the no of protons in the nucleus
Atomic mass no A-The total no of nucleons in thenucleus
Neutron no - the no of neutron in the nucleus
Nuclide- a nucleus with a specific value of Z and A
Element E-A nucleus with a given value of z
Isotope any nucleus that contain the same no ofprotons but different mass no
Radionuclide or radioisotope- any nuclide orisotope which is radioactive
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IsotopesIsotopes
Atoms of the same element (same Z)Atoms of the same element (same Z)but different mass number (A).but different mass number (A).
BoronBoron--10 (10 (1010
B) has 5 p and 5 nB) has 5 p and 5 n BoronBoron--11 (11 (1111B) has 5 p and 6 nB) has 5 p and 6 n
10B
11B
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Figure 3.10: Two isotopes of
sodium.
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Isotopes &Isotopes &
TheirUsesTheirUsesBone scans withBone scans with
radioactiveradioactivetechnetiumtechnetium--99.99.
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Atomic Symbols
Show the name of the element, a hyphen, and
the mass number in hyphen notation
sodium-23
Show the mass number and atomic number
in nuclear symbol formmass number
23 Na
atomic number 11
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Isotopes?Which of the following represent
isotopes of the same element?
Which element?
234
X
234
X
235
X
238
X92 93 92 92
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Counting Protons, Neutrons, andElectrons
Protons: Atomic Number (from periodic table)
Neutrons: Mass Number minus the number of protons(mass number is protons and neutrons because the
mass of electrons is negligible) Electrons:
If its an atom, the protons and electrons must bethe SAME so that it is has a net charge of zero(equal numbers of + and -)
If it does NOT have an equal number of electrons, itis not an atom, it is an ION. For each negativecharge, add an extra electron. For each positivecharge, subtract an electron (Dont add a proton!!!That changes the element!)
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Nucleus vs. Orbitals
Middle of theatom
Protons &Neutrons arefound here
Pathway ofelectrons as they
orbit the nucleus.
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Learning Check Counting
Naturally occurring carbon consists of threeisotopes, 12C, 13C, and 14C. State the number of
protons, neutrons, and electrons in each ofthese carbon atoms.
12C 13C 14C6 6 6
#p+ _______ _______ _______
#no _______ _______ _______
#e-
_______ _______ _______
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Answers
12C 13C 14C6 6 6
#p+ 6 6 6
#no 6 7 8
#e- 6 6 6
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IONSIONS
IONSIONSare atoms or groups of atoms with aare atoms or groups of atoms with apositive or negative charge.positive or negative charge.
Taking awayTaking away an electron from an atom gives aan electron from an atom gives a
CATIONCATION with awith a positive chargepositive charge AddingAdding an electron to an atom gives anan electron to an atom gives an
ANIONANION with awith a negative chargenegative charge..
To tell the difference between an atom and anTo tell the difference between an atom and an
ion, look to see if there is a charge in theion, look to see if there is a charge in the
superscript! Examples: Nasuperscript! Examples: Na++ CaCa+2+2 II-- OO--22
Na Ca I ONa Ca I O
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F
ormingC
ations & AnionsF
ormingC
ations & AnionsF
ormingC
ations & AnionsF
ormingC
ations & AnionsAA CATIONCATION formsformswhen anwhen an atomatom
losesloses one orone or
more electrons.more electrons.
AnAn ANIONANION formsforms
when anwhen an atomatom
gainsgains one orone or
more electronsmore electrons
Mg --> Mg2+ + 2 e- F + e- --> F-
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PREDICTINGION CHARGESPREDICTINGION CHARGESPREDICTINGION CHARGESPREDICTINGION CHARGES
In generalIn general
metalsmetals (Mg)(Mg) lose electronslose electrons ------>> cationscations
nonmetalsnonmetals (F)(F) gain electronsgain electrons ------>> anionsanions
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Learning Check Counting
State the number of protons, neutrons, andelectrons in each of these ions.
39 K+ 16O -2 41Ca +219 8 20
#p+ ______ ______ _______
#no ______ ______ _______
#e- ______ ______ _______
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One Last Learning Check
Write the nuclear symbol form for thefollowing atoms or ions:
A. 8 p+, 8 n, 8 e- ___________
B. 17p+, 20n, 17e- ___________
C. 47p+, 60 n, 46 e- ___________
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EXAMPLE PROBLEM: Atomic Symbols
Write the atomic symbol for the following atoms.
(a) A nitrogen atom containing 7 protons, 8 neutrons, and 7
electrons. (b) A uranium atom containing 92 protons, 143 neutrons, and
92 electrons.
SOLUTION:
(a) 7 15N The atomic numberof nitrogen is equal to the numberof
protons(7) and the mass number is equal to the number
ofprotonsplus the numberof neutrons(7 + 8 = 15).
(b) 92 ,235U The atomic numberof uranium is equal to thenumberofprotons(92) and the mass number is equal to thenumberofprotonsplus the numberof neutrons
(92 + 143 = 235).
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3.2 The Periodic Table
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Organizing The Periodic
Table Elements are given chemical symbols and
arranged by theirunique Atomic Number.
Atomic Number: Tells you the number ofprotons found in the nucleus of an atom.
NOTE: # of protons = # of electrons
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Carbon Isotopes
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THANK U
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assignments
The Chemical Elements and The Periodic Table of theElements
40. Write the chemicalsymbols that represent the followingelements.
a. chlorine
b. zinc
c. phosphorus
d. uranium
43. Write the element names that correspond to the followingsymbols.
a. C
b. Cu
c. Ne
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Identify each of the following as a cation or an anion, anddetermine the charge on each.
a lithium atom with 3 protons and 2 electrons
a sulfur atom with 16 protons and 18 electrons63. Write the atomic number for each of the following
elements.
a. Oxygen
b. Mg c. uranium
d. Li
e. lead
f. Mn
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assignments
The Chemical Elements and The Periodic Table of theElements
40. Write the chemicalsymbols that represent the followingelements. (Obj 11)
a. chlorine Cl
b. zinc Zn
c. phosphorusP
d. uranium U
43. Write the element names that correspond to the followingsymbols. (Obj 11)
a. C carbon
b. Cu copper
c. Ne neon
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Identify each of the following as a cation or an anion, anddetermine the charge on each.
(Obj 22)
a lithium atom with 3 protons and 2 electrons (+3) +(2) = +1 This is a cation with a +1 charge.
a sulfur atom with 16 protons and 18 electrons
(+16) +(18) = 2 This is an anion with a 2 charge.
63. Write the atomic number for each of the followingelements.
a. Oxygen 8
b. Mg 12
c. uranium 92 d. Li 3
e. lead82
f. Mn 25
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a. , and are two common isotopesof hydrogen. What dothese isotopes have in
common? What isdifferent?
b. , and are two common isotopesof carbon. What do theseisotopes have in
common? What isdifferent?