Upload
scarlett-gray
View
223
Download
0
Embed Size (px)
Citation preview
LESSON 2 UNDERSTANDIN
G THE ATOM&
LESSON 3 ELEMENTS AND
CHEMICAL BONDS
THE ATOM The smallest piece of an element that
still represents that element.
The atom is made up of main parts
two
Electron Cloud
Nucleus
THE NUCLEUS A small area in the center of an atom
Responsible for most of the atom’s mass Contains positive charge
Contained in the nucleus:protons
neutrons
PROTONS An atomic particle that has a positive
charge Size: Charge: Location: Atomic Mass Unit (amu) =
Larger than electrons
Positive
Nucleus
1 amu
NEUTRONS Neutral particle that exists in the
nucleus of an atom.
Size: Charge: Location: Atomic Mass Unit (amu) =
Larger than electrons (about the same size as a proton)
NeutralNucleus
1 amu
THE ELECTRON CLOUD The area around an atomic nucleus
where an electron is most likely to be located
Contained in the electron cloud:electrons
ELECTRONS A particle with a negative charge.
Size: Charge: Location: Atomic Mass Unit (amu) =
Much smaller than protons and neutrons
Negative
Electron Cloud
1/1,840 amu
CONTRIBUTORS Democritus Aristotle John Dalton J.J. Thomson Ernest Rutherford James Chadwick Niels Bohr
DEMOCRITUS Proposed that different types of matter
are made from different types of atoms. Proposed that space between atoms
was “empty”
ARISTOTLE 384 – 322 B.C.
Did not believe in Democritus’ idea that between atom’s were empty space
He believed all matter was made of fire, water, air and earth.
JOHN DALTON Late 1700’s All matter is made of atoms that cannot
be created, divided or destroyed. Atoms of the same element have the
same mass and are exactly alike
J.J. THOMSON 1897 Found negatively charged particles
(electrons) and reasoned that they must have a positive charge that balances them out.
ERNEST RUTHERFORD Thomson’s student First atomic model with nucleus Came up with the word proton for
positive charge
JAMES CHADWICK Discovered the neutron Completed the atomic model
NIELS BOHR Proposed that electrons move in circular
orbits, called energy levels, around the nucleus.
ELEMENTS Pure substance made of only one type
of atom A substance made from atoms that all
have the same number of protons.
In the empty box in your notes, look at the periodic table and fill out an elementbox for carbon
CARBON ELEMENT BOX
C
Carbon
12.01
6
Element Atomic Number
Symbol
Atomic Mass
ATOMIC NUMBER The number of protons located in the
atom’s nucleus.
Look at the periodic table …can you find the atomic number in the following element boxes?
Oxygen Potassium Gold
PROTONS AND NEUTRONS The number of of the same
element will always be However, atoms of the same element
can have For example: every carbon atom has 6
protons, however some have 6, 7, or 8 neutrons.
protonsthe same
a different number of neutrons
THESE ARE CALLED… Isotopes - atoms of the same element
that have different numbers of neutrons.
Most elements have isotopes.several
MASS NUMBER The sum of protons and neutrons in an
atom.
AVERAGE ATOMIC MASS The average mass of the element’s
isotopes, weighted according to the abundance of each isotope.
The average atomic mass is and based on each isotope’s
Approximately 99% of Earth’s carbon is which is why carbon’s average atomic mass is close to 12 (12.01)
weightedabundance on Earth
Carbon-12
THE ARRANGEMENT OF ELEMENTS Arranged by:
Arranged in order of:
Periodic-
Dmitri Mendeleev (1834-1907)
Increasing atomic mass
Describes something that occurs or repeats in regular intervals.
The three main regions of elements on the periodic table classify elements asMetals, nonmetals, or metalloids
COLUMNS
The (up and down) columns of the periodic table are called
There are groups
Elements in the same group or family have
vertical
groups or families
Similar chemical and physical properties
18
ROWS The horizontal rows of the periodic
table are called Elements in a period
The first element in a period is usually an active , and the last element in a period is always an inactive .
periods
solidgas
are not alike in properties
ROWS Atomic number (number of protons)
Atomic mass (number of protons + neutrons)
Metals are on the
Non-metals are on the
increases from left to right across a period
increases from left to right across a period
left
right
ENERGY LEVELS Different electrons within an atom have
An electron moves around the nucleus at a distance that corresponds to
Electrons to the nucleus have the amount of energy.
Electrons from the nucleus have the energy.
different amounts of energy
the amount of energy it has.closest
least
furthestmost
Electron Energy Levels
ENERGY LEVELS Negatively charged are strongly
attracted to charged nucleus of an atom.
These OUTERMOST electrons can easily be attracted to the nucleus of
We call these OUTERMOST electrons
electrons
positively
other atoms
valence electrons
ENERGY LEVELS Valence Electrons - outermost electron
of an atom that participates in chemical bonding.
These attractions are what cause chemical bonds
HOW TO DETERMINE THE NUMBER OF VALENCE ELECTRONS The number of in each
atom of an element can help determine
The exception to finding number of valence electrons is
valence electrons
the type and the number of bonds it can form
helium
GROUP #/VALENCE ELECTRON Group 1 Group 2 Group 3-12 Group 13 Group 14 Group 15 Group 16 Group 17 Group 18 Helium is the exception and has V.E.
1 valence electron
2 valence electron
valence electrons vary3 valence electrons
4 valence electrons
5 valence electrons
6 valence electrons
7 valence electrons
8 valence electrons
2
**go back to the periodic table in your notes and label the valence electrons.