chemistry for grade 6-8

2. Lesson 10.1 Using the periodic table
• Trace the development of the periodic table.
• Identify key features of the periodic table.
atomic number: the number of protons in an atom
The periodic table evolved over
time as scientists discovered more
useful ways to compare and
organize the elements.

3. Development of the Periodic Table
• In the 1700s, Lavoisier compiled a list of
all the known elements of the time.

4. Development of the Periodic Table (cont.)
• The 1800s brought large amounts of
information and scientists needed a way to
organize knowledge about elements.
• Dimitri Mendeleev was working a way to
classify elements
• At that time 60 elements had been
discovered.
• He arranged the elements in a list using their
atomic masses
• He noticed that the properties of the elements
seemed to repeat in a pattern

5. Development of the Periodic Table (cont.)
• He noticed when
the elements were
arranged by
increasing atomic
mass, their
properties repeated
every eighth
element.

6. Development of the Periodic Table (cont.)
• When creating his periodic table, Mendeleev
left blank spaces for elements that had not
yet been discovered.
• The term periodic means repeated pattern
• Using periodic properties of the other
elements, he correctly predicted the
properties of scandium, gallium, and
germanium.

7. • Moseley rearranged the table by
increasing atomic number, and resulted
in a clear periodic pattern – our modern
periodic table.
• Periodic repetition of chemical and
physical properties of the elements when
they are arranged by increasing atomic
number is called periodic law.
Development of the Periodic Table (cont.)

8. The Modern Periodic Table
• The modern periodic table contains boxes
which contain the element's name, symbol,
atomic number, and atomic mass.

9. The key element
It shows an element’s
chemical symbol, atomic
number, and atomic
mass
It shows also the state of
matter at room
temperature

10. The Modern Periodic Table (cont.)
• Groups:
• Columns of elements in the periodic table .
• Elements in the same group have similar
chemical properties and react with other
elements in similar ways.
• periods.
• The rows in the periodic table
• The number of each elements increases by
one as you move left to right across a period

11. The Modern Periodic Table (cont.)

12. The Modern Periodic Table (cont.)
• Elements are classified as metals,
non-metals, and metalloids.
• Metals are on the left side and in
the middle
• It is almost three-fourth of the
elements
• All metals are shiny and conduct
thermal energy and electricity

13. • Nonmetals are located
on the right side except
Hydrogen
• Many nonmetals are
gases, and they don’t
conduct thermal energy
or electricity
The Modern Periodic Table (cont.)

14. • Metalloids are located
between metals and
nonmetals
• They have properties of
both metals and
nonmetals
The Modern Periodic Table (cont.)

15. The Modern Periodic Table

16. Lesson 10.2 Metals
• Trace What elements are metals?
• Identify the properties of metals.
Metals : is an element that is generally shiny
Luster : describes the ability of a metal to reflect light
The periodic table evolved over time
as scientists discovered more useful
ways to compare and organize the
elements.

17. Metals
• Metals are elements that are generally shiny
when smooth and clean, solid at room
temperature, good conductors of heat and
electricity, malleable, and ductile.
• Physical properties of metals:
 Luster and conductivity
 Ductility and malleability
 Others

18. Luster and conductivity
• Luster : describes the ability of a metal to
reflect light
Gold is an expensive metal and is used for its
luster
• Conductivity : ability to conduct heat and
electricity
Cupper used in electrical wire not gold
because it is cheap

19. Ductility and malleability
• Ductility : is the ability to be pulled into thin
wires
Gold is the most ductile and malleable metal
• Malleability : is the ability of a substance
to be hammered or rolled into sheets

20. Other physical properties
 Density
 Strength
 Boiling point
 Melting point
All are greater for metals than those of other
elements

21. Chemical properties of metal
 It is the ability or inability of a substance to
change into one or more new substances
 Metals in the same group usually have
similar properties

22. Group 1: Alkali metals
• are all the elements in group 1 except
hydrogen, and are very reactive.
• They have similar chemical properties
• Silvery appearance , soft , the lowest density
they could float on water

23. Group 2: Alkaline Earth metals
• are all the elements in group , react quickly
with other elements
• Always combine with other elements
• They have similar chemical properties
• Silvery appearance , soft , the lowest density
but greater than alkali metals

24. Groups 3-12 Transition elements
• The transition elements are divided into
two blocks
 transition metals in the center of the
table
 inner transition metals includes two
rows in the bottom
• The two sets of inner transition metals are
called :
Lanthanide series - Actinide series.

25. Properties of Transition elements
Higher melting
point
Greater strength
Higher densities
Exist as free
element
Properties

26. Uses of transition elements
Make coins
and jewelry
Make paints
and pigments
Building
materials
Electrical
wires
uses

27. Patterns in properties of metals:

28. Lesson 10.3 : Nonmetals and metalloids
• 96% of the mass of your body comes
from just four elements.
• They are nonmetal
• The other two also nonmetal
• Phosphorous and sulphur
• Six elements form the compounds:
• Proteins , carbohydrates , fats
nucleic acids

29. Lesson 10.3 : Nonmetals and metalloids
• Non-metals are elements that have no
metallic properties
• Non-metals are elements that are
generally gases at room temperature
• Those that are solid are brittle, dull-
looking solids, and poor conductors of
heat and electricity.
• They are used as insulators

30. Lesson 10.3 : Nonmetals and metalloids
• Group 17 is composed of highly reactive
elements called halogens.
• Group 18 gases are extremely unreactive and
commonly called noble gases.
• Groups from 14-18 contain metals ,
nonmetals and metalloids

31. Lesson 10.3 : Nonmetals and metalloids
• Group 18 is called the Noble gases.
• Group 18 includes
 Helium
 Neon
 Argon
 Krypton

32. Lesson 10.3 : Nonmetals and metalloids
• Hydrogen gas
• Has the smallest atomic mass
• It is the most common element in the
universe
• It is classified nonmetal but it has some
properties similar to group 1 alkali metals
• In its liquid form it conducts electricity just like
metal
• On earth it behaves like nonmetal

33. Metalloids
• Metalloids are elements that has
physical and chemical properties of both
metals and nonmetals
• Silicon is the most abundant metalloid in
the universe
• Most sand is made of a compound
containing silicon
• Used in many products

34. Semiconductors
• A property of metalloids is the ability to act as a
semiconductor.
• A semiconductor conducts electricity at high
temperatures, but not at low temperatures.
• At high temperatures, metalloids act like
metals and conduct electricity. But at lower
temperatures, metalloids act like nonmetals
and stop electricity from flowing.
• This property is useful in electronic devices
such as computers, televisions, and solar
cells..