How are atoms studied?

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How are atoms studied?

• Atoms are the building blocks of matter
• Atoms are too small in size to study easily
• Size of Earth soda can soda can atom

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Democritus

• Not until around 460 B.C., did a Greek
  philosopher, Democritus, develop the idea of
  atoms. He asked this question If you break a
  piece of matter in half, and then break it in
  half again, how many breaks will you have to make
  before you can break it no further? Democritus
  thought that it ended at some point, a smallest
  possible bit of matter. He called these basic
  matter particles, atoms.

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Democritus

• He said in the world this was atoms and void.
  No space between the atoms.

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ATOMS
Atoms smallest particle that matter can be
broken down.
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Who studied the atom?

• Studied by many scientists for centuries
• Democritus (400 BC) phrase atomos
• Rutherford (1911) nucleus (gold foil expt)
• Moseley (1913) X-rays to find atomic
• Bohr (1913) planetary model of the atom
• Schrödinger (1923) electron cloud model

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Thomsons Plum Pudding Model

• In 1897, the English scientist J.J. Thomson
  provided the first hint that an atom is made of
  even smaller particles.

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Thomson Model

• He proposed a model of the atom that is sometimes
  called the Plum Pudding model.
• Atoms were made from a positively charged
  substance with negatively charged electrons
  scattered about, like raisins in a pudding.

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Atoms, Molecules and Ions
Atomic Theory of Matter
1806
John Dalton
1. Matter consists of indivisible atoms

• All atoms of a given element
• have identical properties

• Different elements have atoms that
• differ in mass

4. Atoms are indestructible and chemical
reactions are a rearrangement of atoms
5. Compounds contain a definite and small
number of atoms
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Discovery of the Atom
By the early 1800s, John Dalton proposed that
all substances are made up of atoms.
In 1898, J.J. Thomson, proposed that atoms are
made up of smaller parts.
In 1911, Ernest Rutherford, proposed that atoms
have electrons and a positive charged nuclues.
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Parts of an Atom

• Proton - nucleus
• Neutron nucleus
• 3. Electron shells
• Protons and neutrons make up the nucleus and
• has the most mass. Electrons do not weigh as
• much.

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Protons
Protons are located in the nucleus of the atom.
They are positively charged.
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Neutrons
Neutrons are located in the nucleus. They have NO
charge!
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Electrons
Electrons are located in the shells around
the atom. They are negatively charged. Ion a
charged atoms caused by the loss or gain of
an electron.
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Atoms make up substances called elements which
are the building blocks of matter. There are 110
elements
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• 1. ELEMENTS ARE PURE SUBSTANCES MADE OF ONLY 1
  KIND OF ATOM AND ARE THE BUILDING BLOCKS OF
  MATTER.
• 2. ELEMENTS CANNOT BE BROKEN DOWN INTO A SIMPLER
  SUBSTANCE
• 3. ELEMENTS HAVE THEIR OWN UNIQUE SET OF
  PROPERTIES THAT NO OTHER ELEMENT HAS.

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• ELEMENTS ARE MADE OF ONLY 1 KIND OF ATOM
• SOME COMMON ELEMENTS
• HYDROGEN (H), HELIUM (He), OXYGEN (0),
• Notice that the first letter is capital and the
  next letter is lower case.

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Why Do Some Elements Have Different Symbols?
They are older elements that were name in a
different language like Latin. Copper
cuprum Iron Ferrous Gold - aurum Silver -
argentum
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Elements in Organisms

• 4 elements that make up 96 of human body
  Carbon(C), Hydrogen(H), Oxygen(O), Nitrogen(N)

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Element Info in Each Box
Atomic weight Atomic Number Symbol Name
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Information from the periodic table
Atomic Number- Number of Protons in an
atom Silver 47 protons
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Atomic Weight - total number of particles in an
atom's nucleus
Atomic Weight is not very helpful you need to
find the atomic mass
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To find the Atomic Mass Round the atomic weight
Krypton's mass number is 84 since its atomic
weight, 83.80, rounds up to 84.
Mass Number (Number of Protons) (Number of
Neutrons)
84 36 48
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Ways the Periodic Table is Organized

• 1. ELEMENTS ARE ORGANIZED IN THE PERIODIC TABLE
  ACCORDING TO ATOMIC NUMBER

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• 2. ELEMENTS ARE ORGANIZED IN THE PERIODIC TABLE
  OF ELEMENTS ACCORDING TO THEIR SIMILAR
  CHARACTERISTICS
• 3 major groups metals, nonmetals and metalloids

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Arrangement of the Periodic table

• Periods Rows are called periods. The
• Elements in these rows have the same number
• of electron shells.
• 4. Groups Columns are called groups. These
• elements have the same properties because of
• the number of valence electrons.

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Even though they skip some squares in between,
all of the rows go left to right. When you look
at a periodic table, each of the rows is
considered to be a different period (Get it? Like
PERIODic table.). In the periodic table, elements
have something in common if they are in the same
row. All of the elements in a period have the
same number of electron shells. Every element in
the top row (the first period) has one orbital
for its electrons. All of the elements in the
second row (the second period) have two orbitals
for their electrons. It goes down the periodic
table like that. At this time, the maximum number
of electron orbitals or electron shells for any
element is seven.
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Groups
When a column goes from top to bottom, it's
called a group.
Groups are often called families because these
elements seem to be related.
Elements in the same group show similarities in
their chemical and physical properties.
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Electron shells

• Atomic number number of Electrons
• Electrons vary in the amount of energy they
  possess, and they occur at certain energy levels
  or electron shells.
• Electron shells determine how an atom behaves
  when it encounters other atoms

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VALENCE ELECTRONS

• Number of electrons in the outermost. Determines
  how the element will bond.
• GROUPS determined by valence electrons.
• Group 1 one valence electron
• Group 2 2 valence electrons

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Valence Electrons
The number of valence electrons determines how
an atom will bond. The behavior of an atom is
determined by its electrons.
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Determining the valence electrons for some
elements
Li 3 electrons 2 e- in 1st level 1 e- in 2nd
level 1 valence electron
C 6 electrons 2 e- in 1st level 4 e- in 2nd
level 4 valence electrons
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Timberlake, Table 2.15 (7th Ed) Table 2.14 (8th
Ed)
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How do you calculate Valance Electrons?
You determine the number of electrons. Then place
the electrons in electron shells. Bohrs Model
This is a model used to place electrons in
their shells.
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Bohr Diagrams

1. Find your element on the periodic table.
2. Determine the number of electrons it is the
   same as the atomic number.
3. This is how many electrons you will draw.
4. The number of shells are determined by the period.

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Bohr Diagrams

• Find out which period (row) your element is in.
• Elements in the 1st period have one energy level.
• Elements in the 2nd period have two energy
  levels, and so on.

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Bohr Diagrams

1. Draw a nucleus with the element symbol inside.
2. Place Protons and neutrons in the nucleus.
3. Carbon is in the 2nd period, so it has two energy
   levels, or shells.
4. Draw the shells around the nucleus.

C
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Bohr Diagrams

1. Add the electrons.
2. Carbon has 6 electrons.
3. The first shell can only hold 2 electrons.

C
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Bohr Diagrams

1. Since you have 2 electrons already drawn, you
   need to add 4 more.
2. These go in the 2nd shell.
3. Add one at a time -starting on the right side and
   going counter clock-wise.

C
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Bohr Diagrams

1. Check your work.
2. You should have 6 total electrons for Carbon.
3. Only two electrons can fit in the 1st shell.
4. The 2nd shell can hold up to 8 electrons.
5. The 3rd shell can hold 18, but the elements in
   the first few periods only use 8 electrons.

C
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• MOLECULES ARE 2 OR MORE ATOMS ATTACHED TOGETHER
• THEY CAN BE THE SAME KIND (ELEMENTS)
• THEY CAN BE DIFFERENT KINDS (COMPOUNDS)

Examples H2O, NaCl.
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• COMPOUNDS ARE MADE OF 2 OR MORE KINDS OF ATOMS
  BONDED TOGETHER
• FOR A COMPOUND TO FORM, A CHEMICAL CHANGE MUST
  TAKE PLACE (A REACTION)
• THE ELEMENTS THAT COMBINE MAKE A NEW SUBSTANCE
  WITH NEW PHYSICAL PROPERTIES
• COMPOUNDS CANNOT BE BROKEN DOWN PHYSICALLY.
  REQUIRES A CHEMICAL CHANGE
• MORE COMMON THAN ELEMENTS

TABLE SALT
NaCl


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• COMPOUNDS ARE MADE OF 2 OR MORE DIFFERENT KINDS
  OF ELEMENTS.
• COMPOUNDS ARE IDENTIFIED BY A CHEMICAL FORMULA

TABLE SALT
NaCl


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Chemical Changes Through Chemical Reactions
A chemical reaction Process in which the
physical and chemical properties of the original
substance change as new substances with
different properties are formed

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Chemical Formula
Definition Short way to write a compound
using symbols.
Subscript Small number that is written
below the element.
Coefficient The large number in front of the
symbols.
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Chemical Bonds
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Counting Atoms in Compounds
. In compounds you will see elements and in some
compound you will see small numbers behind the
elements, example H2O, that small number is
called a subscript. If the element does not have
a subscript behind it, the subscript is 1.
- The subscript tells you how many of those atoms
are in that compound.  
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Counting Atoms in Compounds
If there is a parentheses in the compound then
you multiply the subscript behind the parentheses
by the subscript that is behind the element in
that parentheses.
Ba(OH)2 1) In this compound there
are three different elements (Barium
Hydroxide) they are Barium (Ba), Oxygen (O) and
Hydorgen (H).  
2) In this compound the subscript 2 goes with the
4. Oxygen is in the parentheses and the
two elements in the paraentheses so there
parentheses are Oxygen (O) and Hydrogen (H). is
2. Same for Hydrogen.
3) Since Ba is not in the parentheses and it
does not
have a subscript there is one Ba.
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Why do elements bond?

• Elements bond to fill their outer shells. This
  make the element stable.
• Elements will either gain, lose or share
  electrons to fill their outer shell.

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Three types of Chemical Bonds

• Chemically combining of two or more atoms
• 1. Covalent Bonds
• Ionic Bonds
• Hydrogen bonds
• These are not all the bonds but all we are going
  to cover.

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Ionic Bonds
In an IONIC bond, electrons are lost or
gained, resulting in the formation of IONS in
ionic compounds.
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Ionic bonding

• Ionic bonding involves 3 steps (3 energies)
• 1) loss of an electron(s) by one element,
• 2) gain of electron(s) by a second element,
• 3) attraction between positive and negative

Ionization energy
Electron affinity
Lattice energy
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Covalent Bonds

• One or more pairs of electrons are shared by two
  atoms

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Covalent IonicCompounds Compounds

• Crystalline solids
• High melting and boiling points
• Conduct electricity when melted
• Many soluble in water but not in nonpolar liquid

• Gases, liquids, or solids
• Low melting and boiling points
• Poor electrical conductors
• Many soluble in nonpolar liquids but not in water

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Octet Rule atoms tend to gain, lose or share
electrons so as to have 8 electrons

• C would like to
• N would like to
• O would like to

Gain 4 electrons
Gain 3 electrons
Gain 2 electrons
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Single Covalent Bonds

• A single covalent bond is one in which two atoms
  share a pair of electrons.
• Structural formulas are chemical formulas that
  show the arrangement of atoms in molecules and
  polyatomic ions.
• Chemical Formula Structural Formula
• H2 H-H
• H2O
• NH3
• CH4

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