atomic structure(lesson )(chapter 1)

8/12/2019 Atomic Structure(Lesson )(Chapter 1)

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ATOMIC STRUCTUREWhat is an ATOM?o All matter is made from atoms

oThe configuration of the atom :

ProtonsNeutrons

Electrons

oThe Atom is the basic buildingblock of everything around us


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Subatomic particle The atoms Protons and Neutrons are in the

Nucleus Protons and neutrons have almost exactly the same

mass.

Protonsare much larger and heavier than electrons.

Neutronsare large and heavy like protons; howeverneutrons have no electrical charge.

The atoms Electrons orbit around the nucleus at

different levels, called shells A shell is sometimes called an orbital or energy level.

Shells are areas that surround the center of an atom.


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Electronsare tiny, very light particles that have a negative electrical

charge (-)

Electrons have a mass that is about 1/1835 the mass of a proton.

The electron is constantly spinning around the center of the

atom (called the nucleus).

In actuality, the electron is a wave that surrounds the nucleus of

an atom like a cloud.

Hydrogen: a proton surrounded by an electron cloud


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Subatomic

particle

Mass (kg) Charge (C) Relative

charge

proton 1.672 x 10-27 1.672 x 10-27 +1

neutron 1.675 x 10-27 0 0

electron 0.910 x 10-30 1.672 x 10-27 -1


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Example

The atom above, made up of one proton

and one electron

The proton and electron stay together,just like two magnets.

A Hydrogen Atom


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Stable configuration Stable elements have equal numbers of

Electrons

Protons

Neutrons

Stable elements have a neutral charge

1 Electron (-) plus 1 Proton (+) plus

1 Neutron (0) =

NO CHARGE


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Atomic number And atomicmass As you add electrons, protons and neutrons, the size of the atom

increases.

We can measure an atom's size in two ways: using the atomic number(Z) or using the atomic mass (A, also known as the mass number).

Z= no. of proton in the element

For hydrogen the atomic number, Z, is equal to 1. For helium Z = 2.

Z also tells you the number of electrons in the neutral atom.

A= Z + N (neutron)

Therefore, the atomic mass, A, of hydrogen is 1. For helium A = 4.


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a.m.u For hydrogen the atomic mass is 1.00797. When we hear

the term atomic mass we think of the mass of an atom.For example the mass of a hydrogen atom is 1.6726 x 10-24 grams. The two numbers are different!

a.m.u is a relative mass to a particular carbon atom.

The carbon atom selected is the carbon atom with 6protons, 6 electrons and 6 neutrons.

1 a.m.u = 1/12 of atomic mass isotope carbon 12

1 amu = 1.6598 x 10-27kg

1 mole of substance= 6.023x1023

atoms/molecules 1 a.m.u/atom or molecule = 1 g/mol

E.g platinium -= 195.08 amu/atom or 195.08 g/mol


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Isotopes and isoton isobar) Isotopes- atoms of the same elements with diff. atomic masses ( dif.

No. of Neutron). For example, an isotope of hydrogen

Isotopes of carbon, C , C, C

Isoton/isobar: Diff. elements with same atomic mass

E.g argon-40 (18p +22 n) and calcium -40 (20 p +20n)

Hydrogen

Atomic Mass = 1

Atomic Number = 1

Deuterium

Atomic Mass = 2

Atomic Number = 1

6

12 13 14

6 6


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Electron configuration of theelements

electron configurationis the arrangement ofelectronsin an atom, moleculeor other body

Electrons are on the shells around the nucleus.

Each shell has a name

The first shell is k

Followed by l, m, n, o, p & q
http://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Atomhttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Atomhttp://en.wikipedia.org/wiki/Electron


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Shells hold only a limited number of electrons

Different shells hold different numbers

K holds only 2 electrons

L holds 8 electrons

M holds up to 18 electrons

Each shell (energy level) consist of subshell

(sublevel), s, p, d, f. Each type of sublevel holds a different orbitals.

An orbital is a space that can be occupied by up to

two electrons


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The number of available electron states in some of the electronshells and subshells

PrincipalQuantum

number, n

ShellDesignation Subshells Number ofstates Number of electron

Per subshell Per shell

1 K s 1 2 2

2 L s 1 2 8

p 3 6

3 M s 1 2 18

p 3 6

d 5 10

4 N s 1 2 32

p 3 6

d 5 10

f 7 14


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Atomic Bonding in solids Three types of primary or chemical bond

are found in solids

Ionic

Covalent inter atomic bonding

Metallic

Secondary Bonding Van der Waals

Hydrogen Bonding


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Ionic Bonding Electron are transferred to form a bond

Often found in compounds composed ofelectropositive elements (metals) and

electronegative elements (non metals)

Na valance

+1

Cl valance -1


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Ionic Bonding GeneralCharacteristics Bonding Energy 150-370 Kcal/mol

Nondirectional Bond- strength of bond equal in

all directions Low electrical conductivity- entire ion must

move to conduct electricity

Transparent, brittle, high melting temperature

Examples- NaCl 183 Kcal/mol, LiF 240

Kcal/mol


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Covalent Bonding Electrons are shared to form a bond
http://en.wikipedia.org/wiki/Image:Covalent.svg


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Covalent Bonding GeneralCharacteristics Bonding energy 75-300 Kcal/mol

Covalent bonding most frequently occursbetween atoms with similar electronegativities.

Directional bond-strength of bond is not equalin all directions

Low electrical conductivity

Very hard, high melting temperature Examples Si 84 Kcal/mol, GaAs 75 Kcal/mol,

Diamond 170 Kcal/mol
http://en.wikipedia.org/wiki/Electronegativityhttp://en.wikipedia.org/wiki/Electronegativity


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Metallic Bonding Founds in metals

and their alloys
http://localhost/var/www/apps/conversion/tmp/scratch_2/New%20Folder/C02METAL.MOV


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Metallic Bonding GeneralCharacteristics Bonding energy 25-200 Kcal/mol

Nondirectional Bond-strength of bond is equal in

all directions

Good electrical conductivity-cloud electron are

free to move to conduct electricity

Ductile, opaque

Examples Na 26 Kcal/mol, Al 74 Kcal/mol, Cu 81Kcal/mol

It involves the delocalizedsharing of free

electronsamong a lattice of metal atoms.
http://en.wikipedia.org/wiki/Delocalizedhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Delocalized


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Secondary Bonding Van der Waals Bonding

Weak secondary bond (< 10 Kcal/mol)

Often bonding force between molecules

Example- PVC can be deformed by breakingVan der Waals bonds between molecules

Hydrogen Bonding

Special type of secondary bond between

some molecules containing H Examplebonds between molecules of

water


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molecules molecule is considered the smallest particleof

a pure chemical substancethat still retains itscompositionand chemical properties.

Most common molecules are bound togetherby strong covalent bonds

i.e F2, O2, H2(diatomic molecules) or H2O, CO2(host of compounds)

The smallest molecule is the hydrogen

molecule
http://en.wikipedia.org/wiki/List_of_particleshttp://en.wikipedia.org/wiki/Chemical_substancehttp://en.wikipedia.org/wiki/Chemical_compoundhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Chemical_compoundhttp://en.wikipedia.org/wiki/Chemical_substancehttp://en.wikipedia.org/wiki/List_of_particles

atomic structure(lesson )(chapter 1)

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