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Elements and the Periodic Table

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'If two elements combine to form more than one compound, ... Their chemical and physical properties are different. from metals. ... – PowerPoint PPT presentation

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Title: Elements and the Periodic Table


1
  • Elements and the Periodic Table

2
  • Classification is arranging items into groups or
    categories according to some criteria.
  • The act of classifying creates a pattern that
    helps you recognize and understand the behavior
    of fish, chemicals, or any matter in your
    surroundings.

3
  • Classifying Matter

4
  • Matter is usually defined as anything that has
    mass and occupies space.

5
Disorder Some space Particles closer together
Order Particles fixed in position
Total disorder Lots of empty space
Gas Liquid
Solid
6
  • Solids, Liquids, and Gases
  • Gases have no defined shape or defined volume
  • Low density
  • Liquids flow and can be poured from one container
    to another
  • Indefinite shape and takes on the shape of the
    container.
  • Solids have a definite volume
  • Have a definite shape.

7
  • Mixtures and Pure Substances
  • A mixture has unlike parts and a composition that
    varies from sample to sample
  • A heterogeneous mixture has physically distinct
    parts with different properties.
  • A homogeneous mixture is the same throughout the
    sample
  • Pure substances are substances with a fixed
    composition

8
  • A classification scheme for matter.

9
  • A physical change is a change that does not alter
    the identity of the matter.
  • A chemical change is a change that does alter the
    identity of the matter.
  • A compound is a pure substance that can be
    decomposed by a chemical change into simpler
    substances with a fixed mass ratio
  • An element is a pure substance which cannot be
    broken down into anything simpler by either
    physical or chemical means.

10
  • Sugar (A) is a compound that can be easily
    decomposed to simpler substances by heating. (B)
    One of the simpler substances is the black
    element carbon, which cannot be further
    decomposed by chemical or physical means.

11
EXAMPLE
  • Isopropyl alcohol is a
  • heterogeneous mixture
  • homogeneous mixture
  • pure substance
  • Compound
  • pure substance and compound

E
12
  • Elements

13
  • Reconsidering the Fire Element
  • The phlogiston theory viewed phlogiston as a
    component of all matter.
  • The burning of a material was considered to be
    the escaping of phlogiston from the matter.
  • If a material did not burn, it was considered to
    contain no phlogiston.

14
  • The phlogiston theory. (A) In this theory,
    burning was considered to be the escape of
    phlogiston into the air. (B) Smelting combined
    phlogiston-poor ore with phlogiston from a fire
    to make a metal. (C) Metal rusting was considered
    to be the slow escape of phlogiston from a metal
    into the air.

15
  • Discovery of Modern Elements
  • Antoine Lavoisier suggested that burning was
    actually a chemical combination with oxygen.
  • Lavoisier realized that there needed to be a new
    concept of elements, compounds, and chemical
    change.
  • We now know that there are 89 naturally-occurring
    elements and at least 23 short-lived and
    artificially prepared.

16
  • Priestley produced a gas (oxygen) by using
    sunlight to heat mercuric oxide kept in a closed
    container. The oxygen forced some of the mercury
    out of the jar as it was produced, increasing the
    volume about five times.

17
  • Lavoisier heated a measured amount of mercury to
    form the red oxide of mercury. He measured the
    amount of oxygen removed from the jar and the
    amount of red oxide formed. When the reaction was
    reversed, he found the original amounts of
    mercury and oxygen.

18
  • Names of Elements
  • The first 103 elements have internationally
    accepted names, which are derived from
  • The compound or substance in which the element
    was discovered
  • An unusual or identifying property of the element
  • Places, cities, and countries
  • Famous scientists
  • Greek mythology
  • Astronomical objects.

19
  • Here are some of the symbols Dalton used for
    atoms of elements and molecules of compounds. He
    probably used a circle for each because, like the
    ancient Greeks, he thought of atoms as tiny,
    round hard spheres.

20
  • The elements of aluminum, Iron, Oxygen, and
    Silicon make up about 88 percent of the earth's
    solid surface. Water on the surface and in the
    air as clouds and fog is made up of hydrogen and
    oxygen. The air is 99 percent nitrogen and
    oxygen. Hydrogen, oxygen, and carbon make up 97
    percent of a person. Thus almost everything you
    see in this picture us made up of just six
    elements.

21
Atomic theory
22
Daltons Postulates
  • Every element is composed of tiny particles
    called atoms
  • All atoms of a given element are identical
  • Atoms of different elements have different
    properties
  • Atoms of an element are NOT changed into atoms
    of another element by chemical processes
  • Matter can neither be created nor destroyed
  • Compounds are formed when atoms of more than
    one element combine

23
Daltons Laws
  • The Law of Constant Composition
  • Any given compound always consists of the same
    atoms and the same ratio of atoms. For example,
    water always consists of oxygen and hydrogen
    atoms, and it is always 89 percent oxygen by
    mass and 11 percent hydrogen by mass
  • 2. The Law of Conservation of Mass
  • The total mass of materials before and after a
    chemical
  • reaction must be the same. For example, if we
    combine
  • 89 grams of oxygen with 11 grams of hydrogen
    under
  • the appropriate conditions, 100 grams of water
    will be
  • producedno more and no less.

24
Daltons Laws
3. The Law of Multiple Proportions If two
elements combine to form more than one
compound, the masses of one of the elements that
can combine with a given mass of the other
element are related by factors of small
whole numbers For example, water has an
oxygen-to-hydrogen mass ratio of 7.91. Hydrogen
peroxide, another compound consisting of oxygen
and hydrogen, has an oxygen-to-hydrogen mass
ratio of 15.81. The ratio of these two ratios
gives a small whole number.
25
MODERN ATOMIC THEORY
26
  • Chemical Symbols
  • There are about a dozen common elements that have
    s single capitalized letter for their symbol
  • The rest, that have permanent names have two
    letters.
  • the first is capitalized and the second is lower
    case.
  • Some elements have symbols from their Latin
    names.
  • Ten of the elements have symbols from their Latin
    or German names.

27
  • Symbols and Atomic Structure
  • A molecule is a particle that is composed of two
    or more atoms held together by a chemical bond.
  • Isotopes are atoms of an element with identical
    chemical properties, but different masses due to
    a difference in the number of neutrons.
  • The atomic mass of an element is the average of
    all the atomic masses of the isotopes.
  • an isotopes contribution is determined by its
    relative abundance.

28
  • The mass of an element is the mass of the element
    compared to an isotope of carbon Carbon 12.
  • Carbon 12 is assigned an atomic mass of 12.00 g.
  • 12.00 is one atomic mass unit
  • The number of protons and neutrons in an atom is
    its mass number.
  • Atomic numbers are whole numbers
  • Mass numbers are whole numbers
  • The atomic mass is not a whole number.

29
Charge (if ion)
Atomic Mass
Symbol
Atomic Number
30
Hydrogen
Protons 1 Neutrons 0 Electrons 1
H
1
1
31
Sodium
Protons 11 Neutrons 12 Electrons 11
Na
23
11
32
Rhenium
Protons 75 Neutrons 111 Electrons 75
Re
186
75
33
Rhenium isotope
Protons 75 Neutrons 112 Electrons 75
Re
187
75
34
EXAMPLE
How many protons, neutrons and electrons are
found in an atom of
Cs
Atomic number protons and electrons There are
55 protons and 55 electrons
Mass number sum of protons and neutrons 133
55 78 There are 78 neutrons
35
  • The Periodic Law

36
  • Dmitri Medeleev gave us a functional scheme with
    which to classify elements.
  • Mendeleevs scheme was based on chemical
    properties of the elements.
  • It was noticed that the chemical properties of
    elements increased in a periodic manner.
  • The periodicity of the elements was demonstrated
    by Medeleev when he used the table to predict to
    occurrence and chemical properties of elements
    which had not yet been discovered.

37
  • Mendeleev left blank spaces in his table when the
    properties of the elements above and below did
    not seem to match. The existence of unknown
    elements was predicted by Mendeleev on the basis
    of the blank spaces. When the unknown elements
    were discovered, it was found that Mendeleev had
    closely predicted the properties of the elements
    as well as their discovery.

38
  • The Periodic Law
  • Similar physical and chemical properties recur
    periodically when the elements are listed in
    order of increasing atomic number.

39
  • The Modern Periodic Table

40
  • Introduction
  • The periodic table is made up of rows of elements
    and columns.
  • An element is identified by its chemical symbol.
  • The number above the symbol is the atomic number
  • The number below the symbol is the rounded atomic
    weight of the element.
  • A row is called a period
  • A column is called a group

41
  • (A) Periods of the periodic table, and (B) groups
    of the periodic table.

42
  • Periodic Patterns
  • The chemical behavior of elements is determined
    by its electron configuration
  • Energy levels are quantized so roughly correspond
    to layers of electrons around the nucleus.
  • A shell is all the electrons with the same value
    of n.
  • n is a row in the periodic table.
  • Each period begins with a new outer electron shell

43
  • Each period ends with a completely filled outer
    shell that has the maximum number of electrons
    for that shell.
  • The number identifying the A families identifies
    the number of electrons in the outer shell,
    except helium
  • The outer shell electrons are responsible for
    chemical reactions.
  • Group A elements are called representative
    elements
  • Group B elements are called transition elements.

44
  • Chemical Families
  • IA are called alkali metals because the react
    with water to from an alkaline solution
  • Group IIA are called the alkali earth metals
    because they are reactive, but not as reactive as
    Group IA.
  • They are also soft metals like Earth.
  • Group VIIA are the halogens
  • These need only one electron to fill their outer
    shell
  • They are very reactive.
  • Group VIIIA are the noble gases as they have
    completely filled outer shells
  • They are almost non reactive.

45
  • Four chemical families of the periodic table the
    alkali metals (IA), the alkaline earth metals
    (IIA), halogens (VII), and the noble gases
    (VIIIA).

46
Metal Elements that are usually solids at room
temperature. Most elements are metals.
Non-Metal Elements in the upper right corner of
the periodic Table. Their chemical and physical
properties are different from metals.
Metalloid Elements that lie on a diagonal line
between the Metals and non-metals. Their
chemical and physical properties are
intermediate between the two.
47
  • When an atom or molecule gain or loses an
    electron it becomes an ion.
  • A cation has lost an electron and therefore has a
    positive charge
  • An anion has gained an electron and therefore has
    a negative charge.

48
  • Elements with 1, 2, or 3 electrons in their outer
    shell tend to lose electrons to fill their outer
    shell and become cations.
  • These are the metals which always tend to lose
    electrons.
  • Elements with 5 to 7 electrons in their outer
    shell tend to gain electrons to fill their outer
    shell and become anions.
  • These are the nonmetals which always tend to gain
    electrons.
  • Semiconductors (metalloids) occur at the dividing
    line between metals and nonmetals.

49
EXAMPLE
What would the charge be on a sodium ion?
Since sodium in in Group IA it is a metal and so
would LOSE an electron
You can tell how many would be lost by the group
number Group 1A elements lose 1 electron
So the charge would be 1
Remember an electron is negatively charged. When
you lose them atom becomes positively
charged… when you gain them it becomes
negatively charged
50
EXAMPLE
How would you right the symbol for the sodium
CATION?
Na
1
How many outer electrons does sodium have before
it loses one?
It has 1…remember the group number!
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