SCIENCE 8

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SCIENCE 8
Third Quarter
Week 7 and 8
Periodic Table of Elements
MELC: Use the periodic table to predict the chemical behavior of an element.
Objectives:
• trace the development of the periodic table;
• identify the different basis of arranging the elements in the periodic table
• identify parts of the periodic table
• explain trends in reactivity, metallic and atomic radius
• arrange elements based on the reactivity, metallic and atomic radius trend
Let’s Try
Multiple Choices. Identify the choice that best completes the statement or answers the question.
Write your answer on a separate sheet of paper.
1. Which law or basis did Johann Wolfgang Dobereiner used in his arrangement of Periodic Table?
A. Triads
B. Periodic Law
C. Law of Octaves
D. None of the above
2. According to periodic law the properties of element vary periodically with what number?
A. Atomic number
B. Number of nuclei
C. Number of neutrons
D. Atomic mass number
3. Which of the following does NOT belong to group IIA?
A. Ba B. Mg C. Na D. Sr
4. Which of the following groups of elements have stable configuration?
A. Alkali metals
B. Alkaline earth metals
C. Halogens
D. Noble gases

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5. Which of the following elements is NOT included in the actinide series?
A. Am B. Cm C. Er D. Np
6. In what period of elements does silver belong?
A. 4 B. 5 C. 6 D. 7
7. Which of the following is a lanthanide?
A. Es B. Eu C. Pu D. Pr
8. Which of the following is the most metallic element?
A. Al B. Ga C. Ge D. Si
9. Which element belongs to group 15 and in the sixth period?
A. At B. Bi C. Po D. Sb
10. All of the following elements are metals EXCEPT?
A. Br B. Co C. Cu D. Zn

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Let’s Explore and Discover
Elements are essential on our daily survival. We use some of them as food, medicine,
hygiene and many more. Some are naturally found in our environment and some are synthetically
made from the laboratory. But, all of them are found and presented in the periodic table of
elements.
This periodic table was developed as a result of years of painstaking work by different
scientists. Its present form was a result of meticulous and thorough study by scientists. The
information and data of every element was arranged and organized in ways that will make it more
understandable, meaningful, and useful.
Historical Development of Periodic Table
The development of the Periodic table could be traced back in 1817 to the work of Johann
Dobereiner, a German chemist who formed the triads of elements with similar properties like the
triad of calcium, barium and strontium. In 1863, John Newlands, an English chemist proposed
the Law of Octaves. He based his classification of elements on the fact that similar properties could
be noted for every eight elements when they are arranged in order of increasing atomic masses.
Around 1869 two scientists determined a way to put the elements in order. Lothar Meyer and
Dmitri Mendeleev both came up with periodic tables that showed how elements should be grouped.
It is interesting to note that these two scientists did not personally know each other, yet they came
up with the same conclusions. Both scientists were teachers living and working in different places.
Meyer lived and worked in Germany while Mendeleev in Russia. Both arranged the elements in
order of increasing atomic mass while putting in groups those with similar properties. Both of
them also left blank spaces in their tables, believing that these spaces would be filled later with
elements yet to be discovered.
Later, in 1914, Henry Moseley, an English physicist observed that the order of the X-ray
frequencies emitted by elements follows the ordering of the elements by atomic number. This
observation led to the development of the modern periodic law which “states that the properties of
elements vary periodically with atomic number”.
The modern periodic table
The modern periodic table organizes elements in
such a way that information about the elements
and their compounds are easily revealed.
• The vertical columns of the periodic table,
called groups, identify the principal
families of elements.
• Some families have their special names.
Refer to the figure on the right,
✓ Group 1 is named as the alkali
metals,
✓ Group 2 as the alkaline earth
metals,
✓ Group 17 as the halogens and
Source: Illustrated in the Grade 8 – Science Learning
Module published on 2013.

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✓ Group 18 as the noble gases.
✓ Groups 13 to 16 are named based on the first element found in their families.
• The horizontal rows are called periods are numbered from the top to bottom. There are 7
horizontal rows or periods in the periodic table.
• Group 3 to Group 12 constitutes one block wherein elements in this block are referred as the
transition elements.
• The lanthanides and actinides are special series of elements but are also part of the
transition block; they are also called the inner transition elements.
• Elements from the taller columns (groups 1, 2, and 13, through 18) are called the
representative elements or main groups of the periodic table.
• A stair step line separates metals and
nonmetals. Elements along the stair step line are
the semimetals.
• The seven elements commonly regarded as
semimetals are boron, silicon, germanium,
arsenic, antimony, tellurium, and polonium.
• The majority of the elements on the left side
of the table are metals. The physical properties of
metals include luster, malleability, ductility, and
conductivity. Metals vary in reactivity.
• The nonmetals are confined to the right
side of the table.
In the Bohr’s model of an atom, an atom has an energy
shell occupied by a specific number of electrons. Each electron shell
can hold only a certain number of electrons. The way the electrons
of an atom are distributed in the various energy levels or electron
shells is called electronic configuration.
The lowest energy level is the one nearest to the nucleus.
This is the energy level that electrons occupy first. It can
accommodate a maximum of 2 electrons. If there are more than 2
electrons, they occupy the succeeding higher energy levels. The
highest energy level that an electron occupies is referred to as the outermost shell or valence shell.
The electrons in the valence shells are called valence electrons. These electrons are the ones
involved in chemical reactions. The chemical properties of an element depend on the number of
valence electrons.
Looking at the table below, Representative elements has their respective valence electron
number. You can see that the number of their old grouping is also the number of their valence
electron. As stated in the Octet Rule elements gain or lose electrons to attain an electron
configuration of the nearest noble gas, to become stable. When an atom/element gains an electron
it becomes negatively charged ion and it is called ANION, while if an atom/element loses an
electron it becomes positively charged ion and it is CATION.
Source: Illustrated in the Grade 8 – Science Learning
Module published on 2013.
Source: https://sites.google.com/site/
comerschemistryclassroom/useful-
links/bohr-s-model-2

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Let’s Practice
This section of the lesson will let you experience sorting out or grouping things. This will
help you get hooked on how scientists have meticulously arranged element in the periodic table.
Activity 1. Sorting: Easy as nuts?
Materials Needed:
✓ a large size pack of mixed nuts (snack junk foods containing different kind such nuts, corn,
peas, etc.)
✓ clean saucers or any small plate will do
✓ timer (any kind of timer can be used)
Procedure:
1. Put the mixed nuts in a plate.
2. Set the timer in two (2) minutes and start sorting the content of the mixed nuts.
Question:
1. Did you finish sorting out the mixed nuts at a given time? ___________________________________.
2. What are your basis in sorting out your mixed nuts. _________________________________________
____________________________________________________________________________________________.
3. How did you find sorting out the mixed nuts? Is it easy/hard? Why? _________________________
____________________________________________________________________________________________
RUBRICS:

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Activity 2. Sorting: How do they do it?
Directions. Fill in the missing data that is needed to complete the identification card of scientist
who contributed in the development of periodic table. Write your answer on a separate sheet
-Illustrations source: https://www.rsc.org/periodic-table/history/about
RUBRICS:

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Let’s Do More
Activity 3: Metal…Metal…How reactive are you?
Materials:
✓ paper
✓ pen/pencil
✓ Periodic Table
Procedure
1. A reaction does not always happen between a metal and a compound. There is an existing
definite order of reactivity existing among metals and hydrogen according to their ability to displace
one another. This arrangement is called the metal reactivity series or activity series of metals. The
activity series is an arrangement of metals according to decreasing order of reactivity, as shown
below.
Q1. Potassium, sodium, lithium are metals belonging to Group 1. In this group, how does
reactivity vary – increasing or decreasing from top to bottom in the periodic table?
_______________________________________________________________________________________________
Q2. Does the relative reactivity of calcium and magnesium follow this trend?
_______________________________________________________________________________________________
Q3. Sodium, magnesium and aluminum belong to Period 2. Does reactivity increase or
decrease from left to right among elements in a period.
______________________________________________________________________________________________
3. From your answer in Q1-Q3, make a generalization of the variation of the reactivity of metals
for those belonging to a group and for those belonging to a period.
_______________________________________________________________________________________________
_______________________________________________________________________________________________
________________________________________________________________________________________.
Source: Illustrated in the Grade 8 – Science Learning Module published on 2013.

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4. Refer to the table, Activity Series of Metals.
Q6. Which will be more reactive in the following pairs of metal in every case?
a. Mg or Na with HCl ____________________________
b. Ag or Al with HCl ____________________________
c. Fe or Zn with CuSO4 ____________________________
Activity 4. Metallic Trendy
Objectives:
✓ compare metallic property of elements
✓ explain the trends in metallic property
Materials Needed:
✓ Periodic Table of Elements
✓ Paper
✓ pen
Procedure:
Refer to the skeleton illustration of periodic table,
metallic character increases from top to bottom and
decreases from left to right as seen in the figure on the
right. Metallic property relates to how easy it is for an
atom to lose an electron. On the other hand, nonmetallic
property relates to how easy it is for an atom to gain an
electron. For instance, If you are going to compare the
following elements which are more metallic:
a. Na and Cs - Cs is more metallic because it belongs to period 6 and metallic
character increases as you go down the group.
b. K an Ga - K is more metallic because it belongs to group 1 and metallic
character decreases as you go across the group.
2. Choose among the pair of elements is more metallic.
a. Be and Ca ___________
b. Cl and F _____________
c. Rb and Li ____________
3. Arrange the following sets of element into increasing metallic character.
a. Si, Mg, S, Na, Cl ____________________________________
b. Te, O, Po, S, Se _____________________________________
Source: Illustrated in the Grade 8 – Science
Learning Module published on 2013.

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Activity 5. Atomic Radius Trends
Objectives:
✓ compare atomic radius of elements
✓ explain the trends in atomic radius
Materials Needed:
✓ Periodic Table of Elements
✓ Paper
✓ pen
Procedure:
1. Study the figure presented.
2. Determine the trend in terms of atomic radius.
3. Choose among the pair of elements bigger atomic
radius.
a. Be and Ca ___________
b. Cl and F _____________
c. Rb and Li ____________
4. Arrange the following sets of element into
increasing size in atomic radius.
a. Si, Mg, S, Na, Cl
____________________________________
b. Te, O, Po, S, Se
_____________________________________
Comprehension Check
Directions: Read and analyze the following questions. Write your answer on your Science study
notebook.
1. What happens to the atomic radius across a period?
_____________________________________________________________________________________________
2. What happens to the atomic radius down a group?
_____________________________________________________________________________________________
RUBRICS:
Source: https://saylordotorg.github.io/text_introductory-
chemistry/s12-05-periodic-trends.html

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What I Have Learned
I. Directions: Answer the questions with the proper information using your notes, book, and the
periodic table. Write your answer on a clean sheet of paper.
1. Define a family. _______________________________________________________
2. What is a period? ________________________________________________________
3. In what period do the following elements belong?
a. He _______________ b. Ge _________________
c. Rb _______________ d. I __________________
4. In what group do the following elements belong?
a. Sulfur _______________ b. Ca _________________
c. Iodine _______________ d. Fe _________________
5. The periodic law states that “______________________________________________________________”
Short Response
What is the importance of a periodic table?
_______________________________________________________________________________________________
_______________________________________________________________________________________________
________________________________________________________________________________________.
RUBRICS:

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Let’s Assess
Multiple Choices. Identify the choice that best completes the statement or answers the question.
Write your answer on a separate sheet of paper.
________1. What was the contribution of Mendeleev in developing the periodic table?
A. discovering protons
B. discovering Mendelevium
C. creating today’s atomic model
D. publishing the first periodic table
________2. What do you call each column of the periodic table?
A. a group
B. a period.
C. an isotope.
D. an element.
________3. What do you call each row of the periodic table?
A. a group
B. a period.
C. an isotope.
D. an element.
________4. According to the periodic law, how do elements that have similar properties appear?
A. to the left of each other
B. to the right of each other
C. at every tenth element
D. at regular intervals periodically
________5. Why do elements within the same group in the periodic table have similar properties?
A. They have the same number ions.
B. They have the same number neutrons.
C. They have the same number protons.
D. They have the same number valence electrons.

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________6. What have you observed in the elements as you move down the same column of the
periodic table?
A. Elements have fewer protons
B. Elements have a lower atomic number
C. Elements have more energy levels
D. Elements have a different group number
________7. What is the tendency of an element having one valence electron?
A. be highly reactive
B. forms ions
C. becomes charged
D. all of the above
________8. Which is not a family of the periodic table?
A. alkaline-earth metals
B. anions
C. halogens
D. noble gases
________9. What do you call atoms that gain or lose electrons?
A. metals.
B. nonmetals.
C. ions.
D. isotopes.
________10. Who proposed the law of octaves which classifies elements based on the fact that
similar properties could be noted for every eight elements when they are arranged in order of
increasing atomic masses?
A. Dmitri Mendeleev
B. Henry Moseley
C. Johann Doberiener
D. John Newlands
Prepared by:
JOEMAR S. CUSTODIO
SST-I
BULBUGAN NATIONAL HIGH SCHOOL
Sta. Maria, Gloria
Division of Oriental Mindoro

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References
Annenberg Foundation (2012). Workshop session 2: The particle nature of matter: Solids, liquids,
and gases. In Essential Science for Teachers: Physical Science. Retrieved
fromhttp://www.learner.org/courses/essential/physicalsci/support/ps_session2.p df
Atkins, Peter, and Jones, Loretta (2002). Chemical Principles: The Quest for Insight, second
edition. New York: W. H. Freeman.
Brady, J.E.,& Senese, F. (2004). Chemistry: Matter and its changes (4th ed.). River Street
Hoboken, NJ: John Wiley & Sons, Inc.
Bucat, R.B. (Ed.). (1984). Elements of chemistry: Earth, air, fire and water, Vol. 2. Canberra City,
A.C.T., Australia.
Chang, Raymond (2002). Chemistry, seventh edition. Boston: McGraw-Hill.
Elvins, C., Jones, D., Lukins, N., Miskin, J., Ross, B., & Sanders, R. (1991).Chemistry one:
Materials, chemistry in everyday life. Port Melbourne, Australia: Heinemann Educational
Australia.
Fricke, M. (1976). "Quantum Mechanics." In Method and Appraisal in the Physical Sciences: The
Critical Background to Modern Science, 1800–1905, ed. C. Howson. New York: Cambridge
University Press.
Fong, P. (1962). Elementary Quantum Mechanics. Reading, MA: Addison-Wesley.
Philippines. Department of Education. 2013. Grade 8 Science Learner’s Module. First Edition.
Meralco Avenue, Pasig City
Philippines. Department of Education. 2013. Grade 8 Teacher’s Guide. First Edition. Meralco
Avenue, Pasig City
Mendoza, E.E. &Religioso, T.F. (1997).Chemistry.Phoenix Publishing House, Inc. Quezon City.
The American Chemical Society (1988).Chemistry in the community.Kendall/Hunt Publishing
Company. Dubuque, Iowa.
Tsaparlis, Georgios. "Atomic Structure." Chemistry: Foundations and Applications.
2004.Encyclopedia.com. 18 May. 2016 <http://www.encyclopedia.com>.

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Answer Key
Let’s Try
1. A 6. B
2. A 7. B
3. C 8. D
4. D 9. C
5. D 10. A
Let’s Assess
1. D
2. A
3. B
4. D
5. D
6. C
7. A
8. B
9. C
10.D
Let’s Practice
Activity 1 and Activity 2. Answers may vary
Activity 3
Q1. The reactivity increases as it goes from top to bottom of the
periodic table.
Q2. Yes, Group 2 metals followed the same trend for Group 1 metals
in terms of reactivity.
Q3. The reactivity decreases as it goes from left to right of the
periodic table.
Q6.
a. Na is more reactive than Mg with HCl
b. Al is more reactive than Ag
c. Zn is more reactive than Fe
Activity 4
2. a – Ca 3. a – Cl, S, Si, Mg, Na
b – Cl b – O, S, Se, Te, Po
c – Rb
Activity 5
3. a – Ca 4. a – Cl, S, Si, Mg, Na
b – Cl b – O, S, Se, Te, Po
c – Rb
Comprehension Check
1. Atomic radius decreases across the period from left to right.
2. Atomic radius increases down a group from top to bottom.
What I Have Learned
1. Answers may vary
2. Answers may vary
3. a – 1 c – 5
b – 4 d – 5
4. a – 16/ VI A / oxygen group
b – 2 / II A / alkaline earth metal
c – 17 / VII A / Chalcogen
d – 8
5. “the properties of elements vary periodically with atomic number”
Short Response (Answers may vary)

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Periodic
Table
of
Elements