atomic structure(lesson )(chapter 1)
TRANSCRIPT
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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
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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
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Metallic Bonding Founds in metals
and their alloys
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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.
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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