Atoms Ppt OriG

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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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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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?

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Atoms Ppt OriG