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
Order
Some space
Total disorder Particles fixed
Particles closer
Lots of empty space in position
together
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
A. heterogeneous mixture
B. homogeneous mixture
C. pure substance
D. Compound
E. 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. Dalton’s Postulates
1.Every element is composed of tiny particles called atoms
2.All atoms of a given element are identical
1. Atoms of different elements have different properties
3.Atoms of an element are NOT changed into atoms of
1. Matter can neither be created nor destroyed
4.Compounds are formed when atoms of more than one

23. Dalton’s Laws
1. 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
produced—no more and no less.”

24. Dalton’s 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 7.9:1.
Hydrogen peroxide, another compound consisting of oxygen and
hydrogen, has an oxygen-to-hydrogen mass ratio of 15.8:1.
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
Atomic Mass
Symbol
(if ion)
Atomic Number

30. Hydrogen
Protons: 1
Neutrons: 0
H
1 Electrons: 1
1

31. Sodium
Protons: 11
Neutrons: 12
Na
23 Electrons: 11
11

32. Rhenium
Protons: 75
Neutrons: 111
186
Re
Electrons: 75
75

33. Rhenium isotope
Protons: 75
Neutrons: 112
187
Re
Electrons: 75
75

34. EXAMPLE
How many protons, neutrons and electrons are found in an
atom of
133
55 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.
– Mendeleev’s 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?
+1
Na
How many outer electrons does sodium have before it
loses one?
It has 1…remember the group number!