Transcript Unit Three

Atoms
Atoms
Atoms are the building blocks of
matter.
“Everything that is something, is
made up of atoms.”
Elements
• A material made from a single type of
atom, which cannot be broken down any
further.
• 90 exist naturally.
Molecules
• A bonded group of
atoms.
• Molecules are the
smallest identifiable part
of a compound that can
exist in a stable state on
its own.
• It has the chemical
properties of that
compound.
Crystals
• Have regular shapes and always have the
same shape as a result of the way
molecules and atoms link together.
• Structure is know as a Crystal Lattice.
• Examples: Salt, Diamond
A regular repeating 3-D pattern
Atoms
• The smallest particle of an
element that still has the
properties of that element.
• Basic building block of
matter.
• Everything is made up of
atoms.
• Are made up of sub-atomic
particles
Evidence for Atoms
• Behavior of
Gasses
– Pressure
• Chemical
Combinations
– Ratios of
ingredients
• Radioactivity
– Reactions with
phosphors
Brownian Motion
-Jerky movement of
particles.
X-Ray Crystallography
-Size and arrangement
of atoms.
Atomic Microscopy
-Actual images of
atoms produced.
Structure of Atoms
Anatomy
of an
Atom
Nucleus – The central part of an
atom made up of Protons and
Neutrons.
Neutron – Particle found in the
nucleus which has No Electrical
Charge, and a mass about the
same size as a Proton.
Proton – Particle in the nucleus,
which has a Positive Electrical
Charge.
Electron – Particle that orbits the
nucleus of an atom and has a
Negative Electrical Charge.
They move more rapidly
around the outer areas of the
atom. Their arrangement
determines the chemical
properties of an atom.
Atom Structure
particle
symbol
“relative”
mass
“relative”
charge
location
proton
p+
1
+1
nuclear
neutron
no
1
0
nuclear
electron
e-
negligible
-1
extra
nuclear
“relative” vs. “absolute”
“relative” “absolute” “relative” “absolute”
particle
mass
mass
charge
charge
p+
1
1.66 x 10-24 g
+1
+1.60 x10-19 C
no
1
1.66 x 10-24 g
0
0
e-
negligible
9.10 x 10-28 g
-1
-1.60 x 10-19 C
Sub-Subatomic Particles
• There are at least 50 fundamental
particles.
• Leptons, Quarks, Antiquarks, Photons,
Gravitons, Bosons, and Gluons.
Scientists infer that sub-subatomic particles are present,
use machines to detect them,
or prove that they have to be
there based on the behavior
of particles.
Atoms
• Rutherford
– Discovered the nucleus.
– Electron orbit the nucleus like planets around the sun.
• Bohr
– Studied light given off by atoms.
– Energy levels
• Remember the Aurora Borealis
– Photons
• Packet of electromagnetic radiation.
• Particle-Like bundle of light.
various atoms are arranged
on
The Periodic Table
Over 100 various kinds of building blocks exist
Elements
• There are over 100 different kinds of
atoms based on the number of P+, N, e• There are 90 naturally occurring elements,
the rest are produced in a lab.
• An element is a substance whose atoms
all have the same number of Protons or
are made of the same atoms.
Elements and the Periodic Table
• Symbol
• Atomic Number
– The number of Protons in each atom
• Mass Number
– The total number of Protons and Neutrons an
atom contains.
• Number of electrons can be calculated
– Every atom has the same number of electrons
as Protons.
• Number of Neutrons can be calculated
– Mass Number minus Atomic Number
Looking at an example we find all sorts of
information.
6
C
Atomic Number
Symbol
Carbon
Atomic Mass
12.0111
Atomic number
(a.k.a. proton number)
•Indicates the # of p+’s an atom has
•Identification Tag of the element
example: each and every C atom has 6 p+’s
5 p+’s would make it B
7 p+’s would make it N
Symbol
•The abbreviated shorthand used to
represent a particular atom
Rules
Atoms are represented by a 1, 2, or in some cases
3 letter Arabic letter code.
The 1st letter is always capitalized; the others (if
there are any) are always expressed in the lower
case.
Be careful using symbols
Po  PO
Atomic Mass
• Indicates the amount of matter present
in an atom
Mass = ( # p+) + ( # no) + (# e-)
But considering the negligible mass of the electron
Mass = ( #
+
p)
+(#
o
n)
Looking back at the original example:
6
C
Carbon
12.0111
#
p+
no
e-
charge
Example #2
#
47
Ag
Silver
107.8682
p+
no
e-
charge
Using the periodic table
• Atomic number
-
unique to each element
equal to the number of protons
equal to the number of electrons
• Atomic weight
average weight of all isotopes of that
element
Isotopes are atoms of the same element with
different numbers of neutrons.
-
Isotopes
• Each isotope has a unique number of
protons plus neutrons called the mass
number.
We said . . .
Mass number = protons + neutrons
various atoms are arranged on
The Periodic Table
Over 100 various kinds of building blocks exist
Protons, Neutrons & Electrons
• Protons
– in
nucleus
– 1 amu
– +1
charge
• Neutrons
– in
nucleus
– 1 amu
– 0 charge
• Electrons
– outside the
nucleus
– 0 amu
– -1 charge
Atomic mass unit (amu) - 1 amu = 1.6606 x 10-27 kg
Atomic charge - 1 electron = -1.6 x 10-19 Coulombs
- 1 proton = +1.6 x 10-19 Coulombs
Identifying elements
• Atomic number (Z)
– the atomic number is equal to the number of
protons in the nucleus
• Mass number (A)
– the mass number is equal to the number of
protons plus neutrons (N) in the nucleus
A=Z+N
Example Problems
Sodium
Chlorine
Nickel
Bromine
Gold
Periodic Table Anatomy
• Metals
– Reactive Metals
– Transition Metals
– Poor Metals
•
•
•
•
•
•
Metalloids
Non-Metals
Lanthanides
Actinides
Groups and Family
On-Line Periodic Table
Group Number / Family
Group 1 – 2, 13 – 18: Main Group Elements
Group 1: Alkali Metals
Group 2: Alkaline Earth Metals
Group 3 – 12: Transition Elements
Group 11: Coinage Metals
Group 15:
Group 16:
Group 17:
Group 18:
Pnictogens
Chalcogens
Halogens
Noble Gases
Electron Configuration
Electron Orbits
• Number of P+ in an atom equals the
number of e• Electrons are arranged in orbits or shells
around the nucleus
• Each orbit can only hold a certain number
of electrons. Max e- per orbit:
– Orbit 1:
2 e– Orbit 2 on: 8+, Variable
Wolfgang Pauli
Subshell
# of Orbitals
s
1
Max # of
Electrons
2
p
3
6
d
5
10
f
7
14
Shell
Subshells
Max Shell
Population
1
1s
2
2
2s 2p
8 (2 + 6)
3
3s 3p 3d
18 (2 + 6 + 10)
4
4s 4p 4d 4f
32 (2+6+10+14)
Electron Configuration
• The arrangement of electrons
– Diagram or Numbers
• Electron configuration determines how an
atom will react with other atoms.
– What it can bond with and what type of bond it
will form.
• Periodic Table Column Numbers
– Number of electrons in outer orbit
Example Problems
Sodium
Chlorine
Potassium
Nickel
Bromine
Gold
Review
• Write out the electron configuration for:
– Helium
– Oxygen
– Calcium
– Iron
– Iodine
– Uranium
– Radon
Shells
• Electron shell = Energy Level
• Valence Shell
– Outermost energy level
Lewis Dot Diagrams
Atomic Spectra
• The most stable state of an atom is when
electrons are at their lowest energy levels.
• Adding energy to an atom can move an electron
up to a higher energy level.
• When the atom releases energy, the electron
falls back to a stable energy level. The move
and the release of the associated energy is
emitted as light.
• Line emission spectra are like fingerprints of
elements.
Oxidation Number
• Charge that results when electrons are
transferred.
• Columns on the periodic table
• Lewis Structure
Ions
What holds it together ?
• Nuclear forces
– strong force - overpowers the electrostatics
force to hold the particles together in the
nucleus
– weak force - involved in beta decay
• Binding energy E = mc2
– energy released in building an atom due to
the difference in the mass of the atom
compared to the mass of the individual
particles
Radioactivity
• The emission of particles or energy
(photons) from the nucleus of an atom
– Alpha particles () - a He nucleus, they have
relatively little penetrating power
– Beta particles () - beta negative (electrons) and
beta positive (same mass as an electron but opposite
sign) have greater penetrating power than 
– Gamma rays ( ) - high energy electromagnetic
waves, similar to light but much higher frequency,
have the greatest penetrating power.
Nuclear reactions
• Fusion - “build up” atomic nuclei releasing
the binding energy
– require extreme temperature
– research in “cold fusion”
• Fission - “break apart” atomic nuclei
releasing neutrons, beta particles and/or
gamma rays
– nuclear reactors
– nuclear bombs