PHY_10_57_V2_TG_Magnetic properties of a substance
PHY_10_57_V2_TG_Magnetic properties of a substance.docx
Theoretical material for the lesson,
definitions for concepts
The magnetic moment of a system measures the strength and the
direction of its magnetism. The term itself usually refers to the magnetic
dipole moment. Anything that is magnetic, like a bar magnet or a loop of
electric current, has a magnetic moment. A magnetic moment is a vector
quantity, with a magnitude and a direction. An electron has an electron
magnetic dipole moment, generated by the electron's intrinsic spin property,
making it an electric charge in motion. There are many different magnetic
behavior including paramagnetism, diamagnetism, and ferromagnetism.
characteristic of transition metals is their ability to form magnets. Metal
complexes that have unpaired electrons are magnetic. Since the last electrons
reside in the d orbitals, this magnetism must be due to having unpaired d
electrons. The spin of a single electron is denoted by the quantum number msms as +(1/2) or
–(1/2). This spin is negated when the electron is paired with another, but
creates a weak magnetic field when the electron is unpaired. More unpaired
electrons increase the paramagnetic effects. The electron configuration of a
transition metal (d-block) changes in a coordination compound; this is due to
the repulsive forces between electrons in the ligands and electrons in the
compound. Depending on the strength of the ligand, the compound may be
paramagnetic or diamagnetic.
Ferromagnetism (Permanent Magnet)
Ferromagnetism is the
basic mechanism by which certain materials (such as iron) form permanent
magnets. This means the compound shows permanent magnetic properties rather
than exhibiting them only in the presence of an external magnetic field
In a ferromagnetic element, electrons of atoms are grouped into domains in
which each domain has the same charge. In the presence of a magnetic field,
these domains line up so that charges are parallel throughout the entire
compound. Whether a compound can be ferromagnetic or not depends on its number
of unpaired electrons and on its atomic size.
Figure 11: Ferromagnetism (a) nonmagnatized material
and (2) Magnetized material with corresponding magnetic fields shown.
Ferromagnetism, the permanent magnetism
associated with nickel, cobalt, and iron, is a common occurrence in everyday
life. Examples of the knowledge and application of ferromagnetism include
Aristotle's discussion in 625 BC, the use of the compass in 1187, and the
modern-day refrigerator. Einstein demonstrated that electricity and magnetism
are inextricably linked in his theory of special
Paramagnetism (Attracted to Magnetic
Paramagnetism refers to the magnetic state
of an atom with one or more unpaired electrons. The unpaired electrons are
attracted by a magnetic field due to the electrons' magnetic dipole
moments. Hund's Rule states that electrons must occupy every
orbital singly before any orbital is doubly occupied. This may leave the atom
with many unpaired electrons. Because unpaired electrons can spin in either
direction, they display magnetic moments in any direction. This capability
allows paramagnetic atoms to be attracted to magnetic fields. Diatomic
oxygen, O2O2 is a
good example of paramagnetism (described via molecular orbital
theory). The following video shows liquid oxygen attracted into a magnetic
field created by a strong magnet:
As shown in the video, molecular oxygen (O2O2 is paramagnetic and is attracted to is paramagnetic
and is attracted to the magnet. In contrast, molecular nitrogen, N2N2, has no unpaired electrons and is diamagnetic; it is
therefore unaffected by the magnet. Diamagnetic substances are characterized by
paired electrons, e.g., no unpaired electrons. According to the Pauli Exclusion
states that no two electrons may occupy the same quantum state at the same time,
the electron spins are oriented in opposite directions. This causes the
magnetic fields of the electrons to cancel out; thus there is no net magnetic
moment, and the atom cannot be attracted into a magnetic field. In fact,
diamagnetic substances are weakly repelled by
a magnetic fieldas demonstrated with the pyrolytic carbon sheet in
Figure 22: Levitating pyrolytic carbon: A small (~6 mm) piece
of pyrolytic graphite levitating over a permanent neodymium magnet
array (5 mm cubes on a piece of steel). Note that the poles of the magnets
are aligned vertically and alternate (two with north facing up, and two with
south facing up, diagonally). Image used with permission from Wikipedia.
Additional guidelines for organizing a
Lesson starts with introducesing the topic of day and spells out the learning outcomes they
will possess after the study. Acquaint students with the following issues:
•The theme of the lesson
•The objectives of the lesson
•The criteria of success for
•The plan of events for the
•Pre-teach the subject
Learners will share their
experiences with magnetic properties of materials. Classify materials as
magnetic, non-magnetic, ferromagnetic, paramagnetic, diamagnetic from assorted
list provide by the teacher.
Then students can deduce topic of the
lessen and objectives, for clarification you can show topic and the learning objectives on the presentation.
vocabulary & terminology will be presented to the students and their
activities during the research work will be explained.
Then teacher will explain the
properties and applications of magnets. Describe, discuse, and explain the
applications of magnets. Ask learners to develop presentations on neodymium
magnets, sensors, seismographs, and metal detectors. Give questions on a
Learners will discuss their
experiences with applications of magnetic substances. Watch videos on left-hand
rule, Ampere force, and Lorentz force. Answers questions about on the videos.Work in groups to develop presentations about
neodymium magnets, sensors, seismographs, and metal detectors. Attempt
questions on the worksheet.
Properties of magnets:
Magnets in daily life:
•Highlights key concepts,
definitions, and equations learnt using the concept map.
•Asks students to do
questions on the worksheet provided.
•Looks forward to the next
•Attempt the questions given
by the teacher.
•Summarize the main concepts,
definitions, and equations learnt.
•Reflect on their own learning.
•Evaluate their own work and
the work of their classmates.
•Complete the flipped reading
and research assignment before the next lesson.
•Complete the specified
thinking tasks for this lesson.
•Should complete worksheet
given by teacher
Additional multilevel (on
assigns questions 1-4 to weak students, questions 5-6 to the
average students, question 1 to the strong students.
Recommendations for formative assessment
Individually work, students will check
themselves teacher prepared answers.
Answers, criteria for
assignments, additional materials for the lesson
Teacher will prepare answer
using theory material
Theoretical material for the lesson, definitions for concepts
This may leave the atom with many unpaired electrons
Learners will share their experiences with magnetic properties of materials