PARTICULATE NATURE OF MATTER- II
Week: Date: Time:
Period:
Duration: Average
age of learners: 15 YEARS
Subject: CHEMISTRY
Class: SS ONE
Topic: PARTICULATE NATURE OF MATTER - II
Sub topic: The constituent of atom and arrangement of
electrons around the nucleus.
Reference materials:
(1) ESSENTIAL CHEMISTRY, TONALD PUBLISHERS, I. O ODESINA
(2) NEW SCHOOL CHEMISTRY, AFRICAN FIRST PUBLISHERS, OSEI YAW
ABABIO
(3) INTERNET
Instructional materials:
Entry behavior: The students have
been familiar with some common element.
Behavioural objective: At
the end of the lesson the students should be able to:
Content
Atomic theory
Structure of the atom
Everything in the world is made up
of atoms.
The structure of the atom is what gives an element its chemical and physical
properties.
Atoms are made up of three smaller
particles:
Electrons
Negatively charged particles that
spin around the positive centre of the atom in circles called energy levels.
Their mass is so small it is nearly zero.
Protons
Positively charged particles that
are contained in the nucleus of the atom
(the centre) they have a mass of 1 amu (atomic mass unit).
Neutrons
Particles with no charge that are
also contained in the nucleus of the atom. They also have a mass of 1 amu.
Electron orbit a central nucleus
of protons and neutrons.
The nucleus has an overall
positive charge as it contains the protons.
|
Particle |
Mass |
Charge |
Location |
|
Electron |
Approx 0 |
-1 |
Energy
level |
|
Proton |
1 amu |
+1 |
Nucleus |
|
Neutron |
1 amu |
0 |
Nucleus |
Every atom has no overall charge
(neutral). While atoms do contain charged particles, they have the same number
of positive protons as negative electrons. These opposite charges cancel each
other out making the atom neutral.
Energy levels and shells
Electrons are arranged in different shells
around the nucleus. The innermost shell - or lowest energy level -
is filled first. Each succeeding shell can only hold a certain number of
electrons before it becomes full. The innermost shell can hold a maximum of two
electrons, the second shell a maximum of eight, and so on. The table gives the
maximum capacity of the first three shells.
Maximum capacity of the first three
shells
|
Energy level or shell |
Maximum number of electrons |
|
First |
2 |
|
Second |
8 |
|
Third |
8 |
A
lithium atom, for example, has three electrons. Two are in the first energy
level, and one in the second.
A
carbon atom has six electrons. Two are in the first energy level, and four in
the second energy level.
A
calcium atom has 20 electrons. Two are in the first energy level, and eight in
the second energy level, eight in the third energy level and two in the fourth
energy level.
Electronic structure
The
electronic structure of an atom is a description of how the electrons are arranged.
For your exam, you need to be able to describe the electronic structure of the
first 20 elements in the periodic table.
The
first 20 elements in the periodic table run from hydrogen to calcium. Their
electronic structures can be shown either as diagrams or numbers. You need to
know how to do both.
Electronic
structure of some elements
(a). Li 2,1 Lithium
atoms have three electrons. Two of these fit into the first energy level, with
the third in the second energy level.
(b). F 2,7 Fluorine
atoms have nine electrons. Two of these fit into the first energy level. The
remaining seven fit into the second energy level.
(c). Ne 2,8 Neon
atoms have ten electrons. Two of these fit into the first energy level. The
remaining eight electrons fit into the second energy level. Because its highest
occupied energy level is full, neon is stable and unreactive.
(d). Na
2,8,1 Sodium atoms have 11
electrons. Two of these fit into the first energy level, eight into the second
energy level. The last one fits into the third energy level.
(e). Ca
2,8,8,2 Calcium atoms have 20
electrons. Two of these fit into the first energy level, eight into the second
energy level, another eight into the third energy level. The last two fit into
the fourth energy level.
(a)
Presentation of teacher activity:
i. The
teacher defines element and list the first- thirty elements.
ii. The teacher defines a compound with
relevant examples.
iii. The teacher explains mixture and their
types
Students’ activities:
i. The students chorus the definition of
element
ii. The students mention example of compound
iii. The students differentiate between the
types of mixture
Evaluation:
The teacher evaluates the lessons by asking the following questions:-
(i)
define element
(ii)
what are the constituents of calcium
hydroxide and potassium iodide
(iii)
Briefly explain a mixture
Assignment
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