Transcript atom

Atomic
Structure
3.1
Atomic History
•In 400 BC a Greek
Philosopher named
Democritus suggested the
universe was made of
invisible units called
atoms.
1800’s John Dalton’s Theory
(Still Accepted)
1. Every element is made of
tiny, unique particles called
atoms
2. Atoms of different elements
can join to form molecules.
John Dalton’s Theory- Disproved
3. Atoms are the smallest
particles and cannot be
subdivided.
4. Atoms of the same element
are exactly alike in mass
JJ Thomson
•Credited with
discovering negative
charged particles called
electrons.
Rutherford
•Credited with discovering
the nucleus.
•Also concluded that
atoms are mostly empty
space.
http://micro.magnet.fsu.edu/electromag/java/rutherford/
Further Research Finding
• Later on, the discovery of protons and
neutrons were discovered in the
nucleus.
• And it was later concluded that all
atoms are neutral in charge.
• The number of protons and electrons in
any atom are always equal.
Niels Bohr
•Suggested that electrons
move around atoms in set
paths around the nucleus.
•He said each path is an
energy level
Today’s Theory
•It has been determined that it
is impossible to pinpoint an
electron’s exact position due to
its tremendous speed.
•Electrons do not move around
in definite paths.
Today’s Theory
•Electrons are found in orbitals
within energy levels. (s, p, d,
and f )
▫a region in an atom where
there is a high probability of
finding electrons.
Today’s Theory
•Electrons are now viewed
as waves vibrating on a
string rather than simple
particles.
•Wave-Particle Duality
Theory
What are atoms?
•The smallest part of an
element that still has the
element’s properties.
Parts of an atom
•Nucleus
▫Proton
▫Neutron
•Electron
Subatomic particles
Nucleus
•center of an atom
•positively charged
•makes up 99.9% of the atom’s
mass
•contains protons and neutrons
Protons
• Charge (+)
• Mass is equal to 1 atomic mass
unit (amu)
• Found in the nucleus
• Identifies the element/atom
Neutrons
•Charge (0) – neutral
•Mass is equal to 1amu
•Found in the nucleus
•Helps determine mass
Electrons
•Charge is negative (-)
•Mass is equal to 0 amu
•Found outside the nucleus, in
the electron cloud
Energy levels
•1st level holds up to 2 e•2nd level holds up to 8 erd
•3 level holds up to 8 or 18 e
•4th level holds up to 8, 18, or 32 e•Outer Level holds up to 8 e(called valence electrons)
Valence Electron
•The number of electrons
in the outermost electron
shell.
•Most important
A Guided Tour of the
Periodic Table
3.2
Periodic
Law
•Properties of elements tend to
change in a regular pattern
when elements are arranged in
order of increasing atomic
number.
Periodic Law
•Periodic Table is set up by
increasing atomic number.
•Atomic Number is the # of
protons in the atom.
Average
Atomic
Mass
Atomic Number
•tells you number of protons
•Never Changes for an atom.
•Appears as a whole # on the periodic
table.
•No two elements can have same
atomic #.
Atomic Number
Atomic
Number
# of
protons
Mass Number
•The mass of an atom
•Total number of protons plus
neutrons in the nucleus of a single
atom.
•Atoms of the same element won’t
always have the same mass number
Mass Number
# of
protons
# of
neutrons
Mass
#
Isotopes
•Any atoms having the same
number of protons but
different number of neutrons.
•So they also have different
mass numbers.
Average Atomic Mass
•Average mass of all known
isotopes for an element
•Found on the periodic table as
a number with a decimal
Atom’s Charge
•They are neutral.
•All atoms have the same
number of protons and
electrons.
•Charges cancel each other out.
Ions
•Charged particles.
•Form when atoms lose or gain
electrons.
•They do this so the ions have a
full outer shell
•Two Types.
Cations
•Positively charged ions.
•Form when atoms lose
electrons.
•Metals
•Left side of table
Cations
•# of protons greater
than # of electrons
•More (+) than (-)
Na Atom
+
Na
Cation
Anions
•Negatively charged ions.
•Form when atoms gain
electrons.
•Nonmetals
•Right side of table
Anions
•# of protons less
than # of electrons
•More (-) than (+)
Cl
Cl atom
Anion
Quantifying atoms or ions
+1
Protons = 3
Neutrons = 7-3 = 4
Electrons = 3
Electrons = 3 -1 = 2
Families of Elements
3.3
Periodic Table
•Periods
-a horizontal row of
elements.
-Tells you the electrons
energy level.
Periodic Table
•Groups (families)
-a vertical column of
elements.
-Tells us the # of valence
electrons and the elements’
chemical properties.
Types of Elements
1. Metals
2. Nonmetals
3. Semiconductors/metalloids
Transition Metals
Inner Transition Metals
Alkali Metals Group 1
•Most reactive metals
•one valence e•Found as compounds (salts) and not
elements due to reactivity.
•As elements they are soft metals and
good conductors.
fun
Alkaline-earth Metals
Group 2
•Less reactive than Alkali
•They are also more commonly
found as compounds
•2 most common are Ca and
Mg.
Transition Metals Groups 3-12
•Less reactive than groups 1
and 2
•Good conductors
Transition Metals
•All solids with the
exception of mercury
•Valuable metals
(Ag, Au, Pt, Cu, Ni, Fe, Co)
Non Metals
•Are not able to conduct
electricity or heat very well.
•Found in groups 13-18, with the
exception of hydrogen
Carbon
• Found as an element (coal, diamond, graphite)
• Found in millions of different compounds
• Called Organic Compounds
HYDROGEN
•It is a gas/nonmetal
•A very explosive gas.
•It is located in group one because it
has one valence electron
• http://video.google.com/videoplay?docid=2380118142773657669&q=hindenburg&hl=en
Oxygen and Nitrogen
•Oxygen is the most common
element found on Earth
•Nitrogen most common gas
found in the atmosphere
Halogens Group 17
•Most reactive nonmetals
•Form salts with group 1
•Used to kill bacteria
•Bromine only liquid
nonmetal
Noble Gases Group 18
•Stable and not reactive. (inert)
•Don’t form compounds.
•They have a full valence shell.
Metalloids
(Semiconductors)
•7 elements on the step
•Properties of both metals and nonmetals.
•Silicon the most familiar
(computer chips)
Inner Transition Metals
•Two rows at the bottom
•Some are Radioactive ex.
Uranium
•93 and greater are all manmade
Moles
3.4
Counting Units
• We buy things by the dozen.
• One dozen = 12 items
• We use the unit mole to count things in
chemistry
Moles
•the SI base unit that
describes the amount of a
substance.
Avogadro’s Constant
•Represents the number of
particles in one mole of a
substance.
•The number is 6.02 x 1023
particles, atoms, or molecules
Moles
•Used for counting with
really tiny atoms
•One mole represents the
atomic mass of an
element.
Molar Mass
•The mass in grams of 1
mol of a substance.
•Using the periodic chart
you can determine the
molar mass of any
element or compound.
Molar Mass Example
•So how many grams in two
moles of Ca?
Solution
•The molar mass of Ca is
40 g/mol.
•2 moles x 40 grams = 80 g
1 mole
Mole Problems
•You can determine how
many moles of a
substance you have if you
know the mass of the
substance.
Example Problem
•If you have 92 grams of
Na how many moles
would you have?
Solution
•MM of Na is 23 g/mole
•92 g x 1 mole = 4.0 moles
23 g