Download File - Mrs. Hale`s Science

What is the Atomic Theory
1. Everything is made up of atoms and atoms cannot
be destroyed.
2. All atoms within a single element are identical.
3. Compounds are formed from two or more
different kinds of atoms.
4. Chemical reactions rearrange atoms.
How did the Atomic Theory
Develop
 Grew as a series of models that developed from
experimental evidence
 Theories and models were revised as more
evidence was collected
Elements
 Matter that is composed of one type of atom
Chemical Symbol
 Elements abbreviated in a specific shorthand –
either a letter or pair of
 If it is a single letter, it is capitalized; C = Carbon
K = Potasium
 If there are two letters, the first is capitalized and
the second is lower case; Cu = Copper
Ar = Argon
Atom
 Smallest piece of matter that still has the properties
of the element
Parts of the Atom
 Protons: positively charged particles (p+)
 Neutrons: Neutral or no charge to the particle (n)
 Electrons: negatively charged particle (e-)
 Nucleus: located in the center of the atom consists
of the proton(s) and neutron(s); electrons surround
the nucleus
Atom
Electron Cloud
 Current model of the atom
 Shows electrons travel in specific energy levels
around a nucleus
 Electrons closest to nucleus have low energy level
 Electrons farther away from nucleus have high
energy level
Bohr Model
 Most used model to illustrate atom
 Resemble planets orbiting the sun or layers of an
onion
Bohr Model
Electron Energy Levels
Electrons in First Three Energy Levels
Energy Level in Atom
Maximum number of
Electrons
1
2
2
8
3
8
Electron Distribution
 Identifies how many electrons are on each level
Masses of Atoms
 The atom is the building block of matter
 Quarks: smaller particles that make up protons
and neutrons – six known to exist
Atomic Mass
 Composed mostly of protons and neutrons in the
nucleus. Also known as the mass number.
Atomic Number
 The number of protons in an atoms; number of
protons also identifies the element
 **If you need to find the number of neutrons of an
atom:
Number of Neutrons = mass number - atomic number (p+)
Elemental Square
The number of protons
Composed of protons and
neutrons of an atom – located in
the nucleus
Isotope
 Atoms of the same element have different number
of neutrons
 Different isotopes have different properties
Average Atomic Mass
Weighted Average mass of an elements
isotope
Common Mass Numbers
Element Symbol
Atomic
#
Proton
Neutron
Atomic
Mass
Ave.
Atomic
Mass
Boron
B
5
5
6
11
10.81amu
Carbon
C
6
6
6
12
12.01amu
Copper
Cu
29
29
24
63
63.55amu
Periodic Table
 Table where elements are organized by
increasing atomic number (number of
protons)
Dmitir Mendeleev
 Late 1800’s he devised the first periodic table
based on atomic mass ~ however some elements
were out of order.
Henry G.J. Moseley
 He arranged elements by atomic number. This is
what is used today!
Arrangement of Periodic Table
 Groups: vertical columns of elements with similar
properties ~ groups are numbered 1-18
 Groups in same column have the same number of
electrons in their outer shell
 The group number tells how many outer level e- an
element holds
 Valence e-: electrons on the outer most energy
level
Arrangement of Periodic Table
 Periods: horizontal rows of elements that contain
increasing numbers of protons and electrons
 Periods are numbered 1-7
Periodic Table
 Read from left to right
 Metals are on left side
 Nonmetals on the right side
 Metalloids on the zigzag line (also known as
semimetals) between the metals and nonmetals
Periodic Table
 Each of the 7 energy levels can hold a maximum
number of electrons
 Period 1 ~ holds 2 e Period 2 ~ holds 8 e Period 3 ~ holds 8 e-
Electron Dot Diagram
 Use element and dots to represent the valence
electrons (outer most level of electrons)
A breakdown of how it works
Recall!!
 Made up of groups – numbers located on the top of
table – tell how many electrons in the last level of
an element (valence electrons)
 Periods – number located down the left side of the
table – tell how many levels (holding the electrons)
an element has
Made up of different
sections
 Metals: Located on the left side of the table ~ has
the most elements in this area
 Nonmetals: Located on the right side of the table ~
made up of mostly gases and includes Hydrogen
(H)
 Metalloids (semimetals): in between the metals
and the nonmetals ~ looks like a zigzag line
Metals
 Physical Properties:
 Luster: shiny and reflective
 Malleable: can be hammered or rolled into flat
sheets or other shapes
 Ductile: can be pulled out or drawn into long
wires
 Thermal conductivity: ability of an object to
transfer heat
 Electrical Conductivity: ability of an object to
carry electrical current
 Low specific heat: only small amount of heat
needed to raise the temperature
Metals
 Chemical Properties:
 Reactivity: Ease and speed in which an element
combines or reacts
 Corrosion: break down of a metal due to chemical
reaction in the environment

Example: rusting or oxidation
 All but Mercury (Hg) are solid at room
Temperature – it is a liquid
Alkali Metals
 Group 1
 Most reactive of all metals; do not occur in nature in
their element form
 Found only in compounds
 Have low density and melting points
Alkaline Earth Metals
 Group 2
 Shiny, ductile, malleable
 Harder and denser with higher melting points
 Combine readily with other elements so very
reactive but not as much as alkali metals (group 1)
 Never found uncombined in nature
Transition Metals
 Groups 3-12
 Most hard and shiny solids except Mercury
 Often have high melting points and densities
 Good conductors
 Very malleable
 Most familiar metals because often occur in nature
uncombined
Lanthanides and Actinides
 Two rows of elements placed below main part of
table
 Atomic numbers 58-71 = lanthanides
 Atomic numbers 90-103 = actinides
Transuranium Elements
 Elements following Uranium (92)
 Are made or synthesized ~when nuclear particles
are forced to crash together
 Use Particle Accelerators that move atomic nuclei
at extreme speeds
Nonmetals
 Physical Properties:
 Lacks most properties of metals; except Hydrogen
 Poor conductors of electricity and heat
 Solid nonmetals are dull and brittle
 Lower densities
 Most are gases at room temperature
Nonmetals
 Chemical Properties
 Most can form ionic bonds (gain or lose valence
electrons) or covalent bonds (share valence
electrons)
Nonmetals Include:
 Gases (Inert gases):
 DO NOT form compounds ~ they have full electron
levels
 Usually non reactive
Nonmetals Include:
 Hydrogen:
 Simplest atom
 Cannot be grouped in a family because chemical
properties very different from other elements
 Make up more than 90% of atoms in the universe
 Only makes up 1% of Earth’s mass
 Rarely found on Earth as pure element ~mostly
combine with oxygen as wate
Also known as semimetals
Semimetals include
 Have metallic and nonmetallic properties
 Solid at room temp
 Brittle, hard and somewhat reactive
 Semiconductors: substance that can conduct
electric current under some conditions but not
others
Mixed Groups
 Include groups 13-17 ~means that metals,
metalloids and nonmetals are together in these
groups