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Electron
theory and Bohr Model of Atom
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All
matter is composed of atoms or groups of atoms (molecules) that are bonded
chemically or physically. To understand the nature of electrical charge, we
must take into account a fundamental model of the atom. The Bohr model, which
depicts a single atom as having a central nucleus and orbiting electrons, is
well-known.
Bohr's Model of an Atom
Bohr’s Model states that in an atom:
- Negatively charged electrons move in defined circular orbits or shells that circle the positively charged nucleus which is sitting in the center.
- The energy levels are represented by an integer (n=1, 2, 3...) known as the quantum number, and each orbit or shell has a set energy.
- An electron is said to be in the ground state (neutral) when it has the lowest possible energy level. The K, L, M, and N shells are assigned to the orbits with n=1, 2, 3, and 4.
- When an electron in an atom needs to go from one energy level to another, it gains the necessary energy, and when it needs to move from one energy level to another, it loses energy.
The
nucleus contains both positively charged protons and electrically neutral
neutrons, which have no charge. The nucleus is orbited by electrons with a
negative charge that is the same size as a proton. These electrons are around
2,000 times lighter than the protons and neutrons in the nucleus.
Positive and Negative Charge
An
atom is typically neutral and has no charge since it contains an equal number
of protons and electrons. However, if we rub two particular materials together,
electrons can go from one substance to another. The atom subsequently gains a
net positive or negative charge, which alters its stability. A positive ion is
created when an atom within a substance loses electrons and becomes positively
charged. A negative ion, on the other hand, is an atom that has gained an
electron and has an excess of negative charge. These charge differences might
have an impact on electrostatics. Your hair may stand on end when your hand or
another differentially charged body is brought close to it if there is a charge
difference between it and the rest of your body, such as that created by
combing your hair with a nylon comb.
Basic Electricity
The
movement of electrons from one location to another is electricity. Although
they can move through any substance, electrons move more readily through some
materials than others. Resistance refers to how easily it flows. A material's
resistance is expressed in Ohms.
Matter
can be broken down into three forms with respect to electron flow:
- Conductors allow for easy electron flow and it have low resistance
- Semi-conductors: Under specific conditions, electrons can be made to flow. Variable resistance depending on the formulation and the state of the circuit.
- Electrons flow very slowly through an insulator and it have high resistance.
Since
electrons are so small, they are typically counted in extremely high
quantities. 6.24 x 1018 electrons make up a Coulomb. Electrons in motion,
however, capture the attention of electricians the most. Current is the term
for the movement of electrons and is expressed in AMPS. A flow of one coulomb
per second over a wire is equivalent to one amp.
Electrons
need to be pulled by an attractive force in order to move past a resistance.
Volts are used to measure the Electro-Motive Force, or EMF. The amount of
effort needed to pass one amp through one ohm of resistance is one volt.
A
resistance generates a certain amount of work as electrons pass through it. It
may manifest as heat, a magnetic field, or motion, but it always has an effect.
This activity is known as Power and is quantified in Watts. One Watt is the
amount of effort that one amp pushing one volt through a resistance can do.
The
number of electrons that will occupy a specific orbit within an atom can be
predicted based on the position of the element in the periodic table. The
orbits or shells that each atom's electrons occupy are determined by their
energy level. Within the atom, electrons occupy each of these shells from the
nucleus outward. These three shells can each hold up to two electrons in the
first, innermost shell, eight in the second shell, and 18 in the third shell.
All
protons and electrons have an electrical charge, but since this charge is so
negligible, we require a more useful unit of charge, which we refer to as the
coulomb. The total charge carried by 6.21 X 1018 electrons is one coulomb (C).
Thus, the charge of a single electron is just 1.61 X 1019 C.
Conductor & Insulator
A
substance is considered a conductor if it has a significant number of free
electrons that can act as charge carriers and allow current to flow freely. A
few examples of effective conductors include iron, gold, copper, and aluminium.
a material that can be easily detached from its parent atom and possesses one
outer electron. A small amount of external energy is required to reject the
nucleus. Electrostatic fields, heat, or light can all produce these energy. An
atom that has been released from its atom and is now free to move about the
crystal structure of the material is said to have a free electron. These free
electrons transform into the charge carriers in a substance. A material that
has a lot of free electrons will conduct heat and electricity well.
An
electric current is said to flow if an external force is applied that causes
the free electrons to move uniformly in a material that normally has free
electrons moving in a random direction.
Metals
are the best conductors because they have a lot of free electrons that can act
as charge carriers. In insulators, the electrons are tightly bound to the
atomic nuclei, preventing them from conducting charge. Insulators include
things made of plastic, glass, rubber, and ceramics.
To
determine the effects of an electric current flow, look for one or more of the
following phenomena: light, heat, magnetism, chemical, pressure, or friction.
For instance, heat is produced when an electric current passes through a
resistive heating element. Light is produced when an electric current flows
through the delicate filament wire in the evacuated bulb of an electric lamp.
Key point
Each
electron has a very little negative electrical charge.
Silver
and copper are two metals that are excellent electrical conductors and easily
sustain the flow of electric current. On the other hand, materials made of
plastic, rubber, and ceramic are insulators and cannot support the flow of an
electric current.
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