Science 9
Q2-Module3
Electronic Structure of Matter
Ions: How They Are Formed?
Lesson
What I Need to Know
Learning Competency: Explain how ions are formed; S9MT-IIe-f-16
Objectives: At the end of this module, you will be able to:
1. describe the general tendencies of atoms.
2. describe how positive and negative ions are formed.
3. classify ions through its composition, kind of charge and magnitude of charge.
What’s In
In the past lesson, you learned that the quantum mechanical model of the atom describes
the atom as having a nucleus at the center. An electron is imagined to be cloud of negative charge
having a certain geometrical shape. The electrons are arranged in principal or main energy levels
that consist of one or more sublevels.
The way in which electrons are distributed in the different orbitals around the nucleus of an
atom is called electron configuration. Filling of electrons start from lower energy level to highest
energy level.
What’s New
Look at the electron configuration of the elements in Group IA, IIA, IIIA, VIA and VIIA. Note
that all elements have inner shells of s2p6 configuration except lithium which has only an s2 or
helium-like inner shell.
Group IA
Example:
Li
- 1s2 2s1
Na
Inner shell
or (He) 2s1
-1s2 2s2 2p6 3s1 or
(Ne) 3s1
Group IIA
Example:
Inner Shell
2
2
Be - 1s 2s
or (He) 2s2
Mg - 1s2 2s2 2p6 3s2 or (Ne) 3s2
Group IIIA
Example:
Inner shell
2
2
1
B
- 1s 2s 2p
or (He) 2s22p1
2
2
6
2
1
Al - 1s 2s 2p 3s 3p
or (Ne) 3s23p1
Figure 1.1Electron configuration of some elements in Group IA, IIA and IIIA
The filled shell may be represented by the noble gas with a similar electron configuration.
The noble gas symbol is followed by the valence shell symbol.
Group IA atoms have electron configurations ending in an s1. This is in the valence shell of
the atom. It contains only 1 electron, hence the number of electrons here indicates the group
number IA.
Group IIA elements have electron configurations ending in s 2, this is also in the valence
shell of the atom. There are only two electrons here, hence the group IIA name.
Group VIA
Example:
Inner shell
O - 1s2 2s2 2p4
or (He) 2s2 2p4
S - 1s2 2s2 2p6 3s2 3p4 or (Ne) 3s2 3p4
Group VIIA
Example:
F - 1s2 2s2 2p5
or
Cl - 1s2 2s2 2p6 3s2 3p5 or
Inner shell
(He) 2s2 2p5
(Ne) 3s2 3p5
Figure 1.2Electron configuration of some elements in Groups VIA, and VIIA
An atom of a VIA element has 6 electrons in its outermost energy level. It tends to attract 2
electrons from another atom during chemical reaction to complete the 8 electrons. By so doing, it
assumes the closed configuration of an inert gas.
In general, outermost s electrons are loosely held by the nucleus. They are lost by the
atom during chemical reactions. By so doing, it assumes the closed configuration of an inert gas
and become very stable.
Other elements tend to have this kind of stability. They are tend to acquire a noble gas
configuration which has eight valence electrons through gaining or losing of electron(s). This is
known as the Octet Rule.
On the other hand, some elements whose outermost energy level is almost filled 6 to 7
electrons tend to share their outer electrons to other atoms to attain stable configuration. Metal
elements tend to lose electrons to become stable while non-metal elements gain electrons to
attain stability.
Activity 1.
Copy and fill out the table below. You may refer your periodic table.
Element
Atomic
Number
Electron
configuration
Ex. Sulfur
Calcium
Phosphorous
Potassium
16
20
15
19
1s22s22p63s23p4
Give up valence
electron or Attracts
electron
attracts electrons
Inert gas it
assumes
(Ne) 3s23p4
What Is It
Atoms have an equal number of protons and electrons and so do not have an overall
charge. The nucleus of an atom is unchanged by ordinary chemical processes, but atom can
readily gain or lose electrons. If electrons are given up (lose) or added (gain) to a neutral atom,
a charged particle called an ion is formed. Ions have an unequal number of protons and
electrons and so have an overall charge.
How do Atoms form Positive ions?
Positive ion is formed when an atom loses an electron to attain stability and has more protons
than electrons and so has a positive overall charge. A (+) charge particle or (+) ion is called
cation (pronounced cat-ion).
The electron configuration of an atom shows how many electrons it must lose or gain to
have a filled outer shell or to become stable. Atoms with a nearly empty outer shell, will lose
electrons to obtain a full outer shell.
Metal atoms, such as sodium, calcium and magnesium, form positive ions. Positive ions
have a small ‘ + ’ symbol and a number by this to indicate how many electrons have been lost.
This number is usually the same as the number of electrons in the atom’s outer shell. The net
charge on an ion is represented by a superscript; +, 2+, 3+ mean a net charge resulting from the
loss of one, two or three electrons respectively.
Examples below show how sodium ion is formed:
Sodium atom: atomic number =11
Sodium ion:
11 protons
=
+11
11 protons
=
+11
11 electrons
=
-11
10 electrons =
-10
Total charge
=
0
Total charge =
+1
Dot and cross diagrams to represents ions of Sodium atom:
+
Loses
1 electron
Na
(barely full outer shell)
Example 2:
Magnesium atom: atomic number=12
12 protons
=
12 electrons =
Total charge =
+
12
12
0
Na
(full outer shell)
Magnesium ion:
12 protons
=
10 electrons =
Total charge =
+
12
10
+
2
-
Dot and cross diagrams to represent ions of Magnesium atom:
2+
Loses
2 electrons
Mg
Mg
( barely full outer shell)
(full outer shell)
How do atoms form negative ions?
Non-metals have high ionization energy and readily take in electron.When non-metal takes
in an electron, there is an imbalance of charges making it negatively charge particle.
An atom that gains an electron to attain stability is called a negative ion and has more electrons
than protons and so has a negative overall charge. A (-) charge particle or negative (-) ion is
called anion (pronounced an-ion).
Non-metal atoms, such as chlorine, oxygen and nitrogen, form negative. Negative
ions have a small ‘ _ ’ symbol and a number by this to indicate how many electrons have
been gained to fill their outer shell. The net charge on an ion is represented by a superscript; -, 2-,
3- mean a net charge resulting from the gain of one, two or three electrons respectively.
Example 1:
How is a fluoride ion formed?
Fluorine atom: atomic number = 9
+9
9 protons
=
-9
9 electrons =
Total charge =
0
Fluoride ion:
9 protons
=
10 electrons =
Total charge =
+9
-10
-1
Dot and cross diagrams to represent ions of Fluorine atom:
-
Gains
1 electron
F
(partially full outer shell)
F
(full outer shell)
Example 2:
How is a sulphide ion formed?
Sulfur atom: atomic number =16
16 protons =
16 electrons =
Total charge =
+16
Sulfide ion:
16 protons =
18 electrons =
Total charge =
-16
0
+16
-18
-2
Dot and cross diagrams to represent ions of Sulfur atom:
2-
Gains
2 electrons
S
(partially full outer shell)
S
(full outer shell)
Try this:
Draw dot and cross diagrams to represent ions of the following atom:
a. Aluminum atom: atomic number=13
b. Oxygen atom: atomic number = 8
What’s More
In this activity, you will classify ions through charges (cation or anions),
composition
(monoatomic or polyatomic), magnitude of charge (uni- or monovalent, divalent, trivalent, and so
on)
Classification of Ions and their Examples
Classification
Examples
By
Monoatomic (composed of only one atom)
Fe2+, Li+, N3-, O2composition
Polyatomic ion (composed of more than one
SO42-, ClO3-, CO32atom)
By kind of
Cation (positive ion)
Na+, Mg2+, Al3+
charge
Anion (negative ion)
Cl1-, O2-, IBy magnitude Monovalent (+1 or -1)
Li+ , K+, OHof charge
Divalent (+2 or -2)
Ca2+, SO42-, Cu2+
Activity 2:
Instruction: Fill in the table below. Write your answer in a separate sheet of paper.
Classification
Ions
Ex. Mg2+
1. NO32.H+
3.P-3
4.CrO42-
Composition
(Mono atonic or
polyatomic)
monoatomic
Charge
(Cation or Anion)
cation
Magnitude of charge
(Monovalent or
Divalent)
divalent
What I Have Learned
Instruction: See some ions inside the banner. Classify ions according to their similarities
and differences by listing them in the appropriate table below:
Ca2+
Cl-
OH-
Na+
ClO3CO32-
IO3Al3+
Similarities:
Cation &
Monoatomic
Differences:
Anion &
polyatomic
Monovalent
Divalent
Trivalent
What I Can Do
In the mountains and on the hills, you feel rested. Why? It is because there is less dust in the
air to consume the negative ions. By the seashores and near the waterfalls, you feel good. The
energy of moving water generates a lot of negative ions.
Instruction: Create a slogan to preserve and protect our mountains, seashores or waterfalls
(just choose one 1). Use 1 short bond paper for your output. Consider the following Rubric in
grading your Slogan:
Category/Value
Relevance/Concept
10 x 4= 40 pts.
Artistic Presentation
10 x 4= 40 pts.
Needs
Improvement-3
Excellent-10
Good-7
Fair-5
The slogan shows
relevance to the
topic,
completeness of
the concept and
clearly visualized.
The slogan shows
relevance to the
topic,
completeness of
the concept, but
the visualization
somewhat unclear.
The concept of
the slogan shows
partially
relevance to the
topic, and
visualization of
the concept is
somewhat
unclear.
The concept of
the slogan is
erroneous or
irrelevant.
Artistic / colorful
presentation of
the slogan is
clearly identified
and visualized.
Artistic / Colorful
presentation of
the slogan is
identified, but it’s
effect is in a
somewhat unclear
manner.
Artistic / Colorful
presentation of
the slogan is
partially
identified, and is
shown in an
unclear manner.
No Art / not
Colorful
presentation of
the slogan
Submission/Completion Used time well
and submitted on
10 x 2= 20 pts.
time.
Used time well
Did the output but Did the output but
but not submitted did not appear
submitted for
on time.
very interesting.
compliance only.
SCIENCE 9: QUARTER 2-MATTER
MODULE 2: STUDENT’S ANSWER SHEET
Name: ____________________ Grade: _____
Section: _________
Score: _____
(A) What I need to know
Activity 1
Atomic
Number
Element
Calcium
20
Phosphorous
15
Potassium
19
Electron configuration
Give up valence
electron or Attracts
electron
Inert gas it
assumes
(B) What Is It (write answers at the back)
(C) What’s More
Activity 2
Classification
Ions
Ex. Mg2+
Composition
(Mono atonic or polyatomic)
monoatomic
Charge
(Cation or Anion)
cation
Magnitude of charge
(Monovalent or Divalent)
divalent
1. NO32.H+
3.P-3
4.CrO42-
(D) What I have Learned
Similarities:
Cation &
Monoatomic
Anion &
polyatomic
Differences:
(E) What I can do (use 1 short bond paper)
Monovalent
Divalent
Trivalent