Atomic structure refers to the organization and composition of atoms, which are the basic building blocks of matter. At the center of an atom lies a dense nucleus composed of protons, which carry a positive charge, and neutrons, which are neutral. Surrounding the nucleus are electrons, negatively charged particles, arranged in shells or energy levels. These electrons orbit the nucleus in specific orbits, with each shell capable of holding a certain maximum number of electrons. The arrangement of these subatomic particles determines an atom's properties, including its chemical behavior and reactivity. Quantum mechanics describes the behavior of particles at the atomic level, revealing the probabilistic nature of electron distribution within an atom. Understanding atomic structure is fundamental to fields such as chemistry, physics, and materials science.

1. The Structure of an
Atom
Prepared by:
Daniel Anore. Oscar Abonita
Jhunalyn Manallo Clarence Borabien

3. Objectives
At the end of 60-minutes period, at least 75% of the students will be able to:
• Understand the different sub atomic particles in an atom in terms of charge
and location
• Create Bohr’s planetary model of an atom
• Appreciate the importance of Bohr’s planetary model in representing atomic
structure of an element

4. Pose your thoughts!
ACTIVITY
Instructions: Guess if the item is true or false. If the answer is true do the “dab pose” and if it is
false do the “uwu pose”.
Questions:
1. The mass of an electron is equal to the mass of a neutron
2. The charges of electron is NEGATIVE
3. According to Bohr’s planetary model, atoms are composed of protons, electrons, and neutrons
4. The atomic structure of an atom is composed of proton, neutrons and electrons
5. The atomic number of an element is the sum of the protons and electrons in the atom

5. What is an atom?
• Smallest unit of an element.
• All matter is made up of atoms.
• Each element has different atoms.
• Atoms can neither be created nor be
destroyed.

6. Molecules
• A molecule is a group of two or more
atoms held together
• The atoms can be the same (an oxygen
molecule has two oxygen atoms) or
different (a water molecule has two
hydrogen atoms and one oxygen atom).

7. The different parts of
atom

8. Protons
• Positively charged part of an
atom, gives the atom it’s
identity
• Located in the nucleus

9. Electron
• Negatively charged part of an
atom
• Located in the electron shell

10. Neutrons
• Neutral or has no charge part
of an atom
• Holds the nucleus together
• Located in the nucleus

11. Nucleus
• Center of an atom, that
contains protons and neutrons

12. Electron shells
• A grouping of electrons in an atom
according to energy.
• The farther a shell is from the nucleus, the
larger it is, the more electrons it can hold,
and the higher the energies of those
electrons.

14. Bohr’s model of an atom
• The Danish physicist Neil Bohr proposed a
new model of the atom in 1915 referred to as
planetary model
• The Bohr model postulates that electrons
orbit the nucleus at fixed energy levels.
• Orbits further from the nucleus exist at
higher energy levels.

15. Bohr’s model of an atom
• Electrons are arranged in Energy Levels or Shells around the nucleus of an
atom.
• first shell a maximum of 2 electrons
• second shell a maximum of 8 electrons
• third shell a maximum of 18 electrons

16. Maximum number of electrons per shell

17. Atomic structure of an element
• The number of protons In an atom is known as its atomic number.
• The mass number is the total number of protons and neutrons in the nucleus of
an atom.
• To calculate the numbers of subatomic particles in an atom, use its atomic number
and mass number:
1. Number of protons = atomic number.
2. Number of electrons = atomic number
3. Number of neutrons = mass number – atomic number

18. Let’s have an example!
Draw the atomic diagrams of the following elements showing the distribution
of – protons, neutrons & the electrons in various shells of the atoms
Wherein:
Atomic number = protons = electrons
Atomic mass = neutrons + protons
Neutrons = Atomic mass – atomic number
1. Helium (He)

20. Short quiz
A. Multiple choice: Choose the letter of the best answer
1. The 3 basic components of an atom are:
a. Protons, neutrons, and Electrons
b. Quarks, neutrons, and Electrons
c. Protons, neutrinos, and Ions
d. Protons, neutrons, and İons
2. The nucleus of an atom consists of
a. Protons and neutrons. c. Protons and electrons
b. Neutrons. d. Electrons
3. Orbiting the central region of an atom are negatively
charged
a. Protons b. Electrons c. Neutrons d. Nuclei
4. This is a model used to represent atomic structure
a. Bohr’s atomic model c. Atomic shell model
b. Atomic structure d. All of the above
5. It is the placed where electron is located
a. Electron orbits/shell c. Orbits
b. Shell. d. All of the above
B. Identification
1. This is the center of an atom
2. Danish physicist who proposed a new model of the
atom in 1915
3. Made up of smaller particles called protons, neutrons
and electrons
4. The number of electron and protons is equivalent of
what?
5. The arrangement of subatomic particles within the
atom.

21. Activity: Bohr’s model of an element
Instruction: Group yourself into 4 groups. Each group are task to make a 2D
Bohr’s model of assign element
Sodium (Na) Calcium (Ca) Neon (Ne) Magnesium (Mg)

22. Assignment
• Study the development of the periodic table from observations based on
similarities in properties of elements