Structure of Atoms by hJT9vr


									Atomic Structure
   Matter is made of tiny particles called atoms.
   There are three basic types of particles that
    make up an atom:
       Protons
       Neutrons
       Electrons
   The dense center of the atom is called
    the nucleus.
   The particles that are located in the
    nucleus are protons and neutrons.
   Protons are particles that have a
    positive charge.
   Neutrons have no charge and are
    therefore neutral.
   The electrical charge of the nucleus is
   The nucleus contains most of the
    atom’s mass.
   The negatively charged
    particles of an atom
    that exist outside the
    nucleus are called
   They travel in an orbit usually close to the
    nucleus called an electron cloud.
   The structure of the different
    types of atoms and how they
    are joined together (how
    they are bonded to each
    other) determine what the
    substance is.
   Example: graphite, coal and
    diamonds are all made of
    atoms of carbon.
   An element is a substance that is
    made of only one type of atom and
    cannot be broken down into simpler
    substances by normal chemical or
    physical means.
    The number of protons in an atom will
     determine what kind of element it is.
    All atoms of the same element
     have the same number of protons.

Hydrogen and Helium atoms    Carbon atom
     Periodic Table of the Elements
   The periodic table is a listing of all the
    known elements that exist in the world.
   The number of protons in an atom is
    equal to the atomic number of the
    element. You will find it above the
    element’s symbol on the table.
   When you look at the table you will
    notice that the elements are listed in
    order of their atomic number from left to
KEY   Metals   Semimetals   Nonmetals
 A neutral atom is one that has an equal
  number of protons and electrons.
 The overall charge is therefore neutral.

 In a neutral atom: Atomic number = # of

  protons = # of electrons
   The atomic mass of an atom is equal to
    the number of protons plus the number
    of neutrons.
   You can determine the number of
    neutrons by subtracting the number of
    protons from the atomic mass.
          Atomic Structure of 14 Elements

Element     Symbol   Atomic    Mass    Element     Symbol   Atomic    Mass
                     Number   Number                        Number   Number
Hydrogen     H          1       1      Calcium      Ca        20       40
Helium       He         2       4      Iron         Fe        26       56
Oxygen       O          8       16     Sulfur       S         16       32
Carbon       C          6       12     Sodium       Na        11       23
Neon         Ne        10       20     Chlorine     Cl        17       35
Nitrogen     N          7       14     Potassium    K         19       39
Magnesium    Mg        12       24     Argon        Ar        18       40
      Energy Levels
   An energy level represents the area in an atom where an
    electron is likely to be found.
   Each energy levels can hold only a limited number of
   The smallest, innermost energy level
    can hold only two electrons.
   The second energy level can hold up
    to eight electrons.
   The third energy level can hold up to
    8 electrons.
   The 4th & 5th can hold up to 18 electrons.
   The 6th can hold up to 32 electrons.
   Electrons tend to occupy the lowest
    available energy level.

   The first energy level in an
    aluminum atom is filled by two
   The second energy level is also
    filled, by eight electrons.

   The third energy level has only three electrons, so it
    is not filled.
   The number of electrons in the outermost
    energy level determines the chemical
    behavior of the different elements.
   These outermost electrons are called valence
   Elements with the same number of valence
    electrons have similar chemical properties.
   For example, a sodium (Na)
    atom, with the atomic number
    11 and a potassium (K) atom,
    with the atomic number 19,
    both have just one valence

   Both sodium and potassium are
    highly reactive metals, which
    means that they combine easily
    with other elements.
   Elements such as helium (He), neon
    (Ne) and argon (Ar) are inert, which
    means that they do not easily combine
    with other elements.
   This is because they have full outermost
    energy levels.
    Classifying Elements
   Each element has a name and a symbol.
   The symbol is an abbreviated , or
    shortened version, of the element’s name.
                               Aurum is the Latin
                               name for gold.

   It is used to represent the element in
    chemical formulas and equations.
   The elements in the Periodic Table are
    arranged so that elements with similar
    properties are close together.
   Example: fluorine (F) and chlorine (Cl) are gases that
    react very easily with other elements, so they are
    close together in the table.
   The Periodic Table gets its name from the fact
    that the elements’ properties repeat
    themselves every few elements, or
   The vertical columns of elements are called groups.
   Some groups have special names:
       Group 1:    The alkali metals
       Group 2:    The alkaline earth metals
       Group 17:   The halogens

       Group 18:   The noble gases – unreactive, so they
                    almost never react with other elements
                    to make compounds.
                The Periodic Table

Column = Group or
18 columns on the
  Periodic Table

 Row = Period
7 rows on the
Periodic Table
   The horizontal rows of elements are
    called periods.
   The table also shows which elements
    are metals, non-metals, and metalloids.
    Metals             All metals look shiny.

   Most metals are very hard (a few so soft you can
    cut them with a knife).
   Metals are also malleable, meaning that they can
    be bent, or beaten into different shapes without
   All metals except mercury are solids at room
    temperature because they generally have high
    melting and boiling points.
   All metals let heat and electricity pass through
    them easily, so they are good conductors of heat
    and electricity.
   Only a few metals are magnetic (ex. - iron).
   At room temperature most nonmetals are
    gases, some are solids and one (bromine) is a
   This is because nonmetals have a wide range
    of melting and boiling points.
   Nonmetals are not good conductors of
    electricity or heat (with the exception of
    carbon, which conducts electricity as well as a
   All nonmetals are nonmagnetic.
   A few elements, such as silicon, have some of the
    properties of metals and some of the properties of
   Since they are not clearly one or the other, they are
    called metalloids, or semimetals.
   They are used in making semiconductors – materials
    which can conduct some electricity better than an
    insulator can, but not as well as a metal.
   They are used in making electronic components and
   A compound is a substance
    that is made up of different
   The atoms of the elements are joined
    together by chemical bonds.
   Bonds are chemical connections between
Types of Bonds
   There are two basic types of bonds:
       Covalent
       Ionic
   The reason that bonds occur is that atoms
    “want” to have full outer electron shells.
   An atom gets a full outer shell by getting
    involved in one of the two types of bonds.
      Covalent Bonds
   Sharing one of more
    electrons is one type of
    bonding called a covalent
   Example: water is formed
    when atoms of hydrogen
    share their electrons with
    an oxygen atom.
   A molecule is the smallest unit of a compound
    that has all the properties of the compound.
       Ionic Bonds
   The second type of bonding is when some atoms
    give up electrons, or ionic bonding.
   Example: salt is formed
    when the sodium gives
    up its electron and the
    chlorine takes it.

   An atom like this that has lost or gained an
    electron is called an ion.
   We write a + next to the
    element’s symbol if its
    atom has lost an electron
    and a – if it gains an
   For example: Na becomes Na+ because it has more
    positive charge than negative and Cl becomes Cl-
   Opposites attract! The protons in the nucleus “miss” the
    “missing” electron and they stay close to it forming the
   If two types of atoms bond together using
    either method, the result is a compound.
   In a chemical change, bonds are made or
    broken, which leads to a new substance, or
    substances being created.
   In a physical change, such as making a
    mixture or dissolving something, no bonds
    are affected.
                             A mixture is a combination of
       Mixtures               things where there are no
                              chemical changes or bonds.

   There are two types of mixtures:
   Heterogeneous:      Not mixed evenly
                        Each component retains its own
                        Examples: pizza, cereal and milk, rocks
                         in the sand at the beach, banana splits
   Homogeneous:        Mixed evenly throughout
                        Properties are often different from their
                        Examples: milk, kool-aid, blood, lotion,
                         window cleaner, glue
   A solution is an evenly mixed mixture
    (liquid), such as salt water.
   Mixtures can be separated by physical
   An isotope is an atom that has the same
    number of protons as another atom, but
    has a different number of neutrons.
   Atoms of an element can lose or gain
    electrons and still be the same element, but
    the atom is no longer neutral. If the number of
    electrons is less than the number of protons,
    the atom will have a positive charge. Atoms
    with more electrons have a negative charge.
    Atoms of the same element with a different
    number of electrons are called ions.

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