Atomic Structure
Atomic structure is the backbone of chemistry as it helps to explain the properties and
behaviors of elements. It is a basic understanding that tells how atoms are composed of
subatomic particles: protons, neutrons, and electrons, their arrangements in various energy
levels or orbitals, and their behavior in chemical reactions.
1) Subatomic Particles
An atom is composed of three major subatomic particles:
Protons (p⁺)
Found in the nucleus
Carry a positive charge
The number of protons determines the atomic number (Z) and, hence, the identity of the element
Neutrons (n⁰)
Found in the nucleus
Carry no charge (neutral)
Their number, together with protons, determines the mass number (A)
Electrons (e⁻)
Found in orbitals around the nucleus
Carry a negative charge
The number of electrons is equal to the number of protons in a neutral atom
2) Bohr’s Model of the Atom
In 1913, Niels Bohr proposed a model explaining the behavior of electrons in
hydrogen atoms. His model was based on the following concepts:
Energy Levels (Shells): Electrons revolve around the nucleus in circular
orbits called energy levels (or shells). Each shell has a specific energy,
and the further the shell is from the nucleus, the higher the energy level.
Quantization of Energy: Electrons can exist only in certain energy levels.
They absorb or emit energy when they jump from one energy level to
another.
Equation for Energy Levels: En = −13.6
n2 eV
Atomic structure is the backbone of chemistry as it helps to explain the properties and
behaviors of elements. It is a basic understanding that tells how atoms are composed of
subatomic particles: protons, neutrons, and electrons, their arrangements in various energy
levels or orbitals, and their behavior in chemical reactions.
1) Subatomic Particles
An atom is composed of three major subatomic particles:
Protons (p⁺)
Found in the nucleus
Carry a positive charge
The number of protons determines the atomic number (Z) and, hence, the identity of the element
Neutrons (n⁰)
Found in the nucleus
Carry no charge (neutral)
Their number, together with protons, determines the mass number (A)
Electrons (e⁻)
Found in orbitals around the nucleus
Carry a negative charge
The number of electrons is equal to the number of protons in a neutral atom
2) Bohr’s Model of the Atom
In 1913, Niels Bohr proposed a model explaining the behavior of electrons in
hydrogen atoms. His model was based on the following concepts:
Energy Levels (Shells): Electrons revolve around the nucleus in circular
orbits called energy levels (or shells). Each shell has a specific energy,
and the further the shell is from the nucleus, the higher the energy level.
Quantization of Energy: Electrons can exist only in certain energy levels.
They absorb or emit energy when they jump from one energy level to
another.
Equation for Energy Levels: En = −13.6
n2 eV
