Chapter 1 Atomic Structure and the Periodic Table
1.1 The Nature of Chemistry
• What is Chemistry?
Matter: anything that has mass and takes up space.
The study of chemistry explores matter and its interactions, a process for acquiring
knowledge.
Chemistry is often called as the central science.
It helps to connect physical science (physics) and life science (biology).
Concepts in chemistry are often based on the understanding of the laws of physics.
E.g., The concept of ionic bonding is based on the understanding that opposite electrical
charges attract one another.
The study of chemistry is subdivided into various branches: inorganic chemistry, organic
chemistry, nuclear chemistry, biochemistry, and physical chemistry.
Chemistry involves both experimenting in the macroscopic world and theorizing about the
microscopic world.
• Chemistry at Work
Empirical knowledge: knowledge that comes from investigation and observation.
For example: In the late twentieth century, scientists discovered traces of a new form of
carbon, C60. They found that pure C60 is an extremely stable substance that is able to
withstand extremely high temperatures and that has low solubility in water.
Theoretical knowledge: knowledge that explains scientific observations.
For example: Harold Kroto, Robert Curl, and Richard Smalley were awarded the Nobel Prize
in Chemistry in 1996 for their roles in its discovery. They proposed that its molecular shape
resembles a soccer ball, with the carbon atoms forming the pentagons and hexagons on the
surface of the sphere. Images of soccer balls and architectural domes helped chemists to
imagine what these molecules might look like on a molecular scale.
Theory: an explanation / model based on observations, experimentation and
reasoning.
,• IUPAC and the Scientific Community (established in 1919)
IUPAC = The International Union of Pure and Applied Chemistry
à was set up to help regulate standards and procedures in chemistry, promote
the international aspects of chemistry and apply chemistry to the service of humanity.
1.2 Atomic Structure
• Dalton’s Atomic Theory
Atom: the smallest particle of an element
In 1808, English scientist and schoolteacher John Dalton proposed a theory to explain the
observations of matter, suggesting that atoms are solid spheres like billiard balls.
Dalton proposed that
o All matter is made up of tiny, invisible particles called atoms
o All atoms of an element are identical (WRONG)
o Atoms of different elements are different
o Atoms are rearranged to form new substances in chemical reactions (WRONG), but
they are never created or destroyed.
• Thomson’s Discovery of Electron
In 1897, J.J Thomson used an apparatus called a cathode ray tube to discover a “new” type
of particle: the electron.
Electron: a negatively charged particle in an atom or ion.
A new model of the atom now included electrons spaced evenly in a positively charged
sphere: the “plum pudding model”, where the fruit represents the electron.
• Rutherford’s Discovery of the Nucleus
In 1909 Ernest Rutherford performed a series of important experiments to test Thomson’s
model.
In 1920, Rutherford proposed that the nucleus is made up of positively charged particles,
each one called a proton, suggesting that the nucleus is surrounded by mostly empty space
occupied by electrons (knowns as the nuclear model).
Nucleus: a positively charged particle in the atom’s nucleus.
• Chadwick’s Discovery of Neutrons
In 1932, James Chadwick’s experiments confirmed that nuclei contain neutral particles
(became known as neutrons) as well as protons.
Neutron: a neutral particle in an atom’s nucleus.
, Has no charge: it’s neither +ve or -ve.
• Bohr’s Proposal of Evergy Levels
Further work was performed by Niels Bohr, a Danish scientist.
Bohr’s observation led to a radical new proposal: that electrons orbit the nucleus of the atom
in definite energy levels. Bohr had again revised the model of the atom. His revision is called
the planetary model of the atom.
In the planetary model, electrons only exist in certain allowed orbits. Each orbit has a specific
quantity of energy associated with it. As a result, electron orbits are sometimes called energy
levels. Electrons can jump from and to different energy levels within an atom. As they jump
from higher energy levels back down to lower energy levels, they emit light energy. The
colours of light emitted by the excited hydrogen atoms correspond to the changes in energy
that the electrons experience as they move between energy levels. Since he observed only
certain colours, Bohr suggested that an atom has only certain specific energy levels.
Energy Level: a theoretical sphere around an atom where electrons exist; electron
orbit.
1.1 The Nature of Chemistry
• What is Chemistry?
Matter: anything that has mass and takes up space.
The study of chemistry explores matter and its interactions, a process for acquiring
knowledge.
Chemistry is often called as the central science.
It helps to connect physical science (physics) and life science (biology).
Concepts in chemistry are often based on the understanding of the laws of physics.
E.g., The concept of ionic bonding is based on the understanding that opposite electrical
charges attract one another.
The study of chemistry is subdivided into various branches: inorganic chemistry, organic
chemistry, nuclear chemistry, biochemistry, and physical chemistry.
Chemistry involves both experimenting in the macroscopic world and theorizing about the
microscopic world.
• Chemistry at Work
Empirical knowledge: knowledge that comes from investigation and observation.
For example: In the late twentieth century, scientists discovered traces of a new form of
carbon, C60. They found that pure C60 is an extremely stable substance that is able to
withstand extremely high temperatures and that has low solubility in water.
Theoretical knowledge: knowledge that explains scientific observations.
For example: Harold Kroto, Robert Curl, and Richard Smalley were awarded the Nobel Prize
in Chemistry in 1996 for their roles in its discovery. They proposed that its molecular shape
resembles a soccer ball, with the carbon atoms forming the pentagons and hexagons on the
surface of the sphere. Images of soccer balls and architectural domes helped chemists to
imagine what these molecules might look like on a molecular scale.
Theory: an explanation / model based on observations, experimentation and
reasoning.
,• IUPAC and the Scientific Community (established in 1919)
IUPAC = The International Union of Pure and Applied Chemistry
à was set up to help regulate standards and procedures in chemistry, promote
the international aspects of chemistry and apply chemistry to the service of humanity.
1.2 Atomic Structure
• Dalton’s Atomic Theory
Atom: the smallest particle of an element
In 1808, English scientist and schoolteacher John Dalton proposed a theory to explain the
observations of matter, suggesting that atoms are solid spheres like billiard balls.
Dalton proposed that
o All matter is made up of tiny, invisible particles called atoms
o All atoms of an element are identical (WRONG)
o Atoms of different elements are different
o Atoms are rearranged to form new substances in chemical reactions (WRONG), but
they are never created or destroyed.
• Thomson’s Discovery of Electron
In 1897, J.J Thomson used an apparatus called a cathode ray tube to discover a “new” type
of particle: the electron.
Electron: a negatively charged particle in an atom or ion.
A new model of the atom now included electrons spaced evenly in a positively charged
sphere: the “plum pudding model”, where the fruit represents the electron.
• Rutherford’s Discovery of the Nucleus
In 1909 Ernest Rutherford performed a series of important experiments to test Thomson’s
model.
In 1920, Rutherford proposed that the nucleus is made up of positively charged particles,
each one called a proton, suggesting that the nucleus is surrounded by mostly empty space
occupied by electrons (knowns as the nuclear model).
Nucleus: a positively charged particle in the atom’s nucleus.
• Chadwick’s Discovery of Neutrons
In 1932, James Chadwick’s experiments confirmed that nuclei contain neutral particles
(became known as neutrons) as well as protons.
Neutron: a neutral particle in an atom’s nucleus.
, Has no charge: it’s neither +ve or -ve.
• Bohr’s Proposal of Evergy Levels
Further work was performed by Niels Bohr, a Danish scientist.
Bohr’s observation led to a radical new proposal: that electrons orbit the nucleus of the atom
in definite energy levels. Bohr had again revised the model of the atom. His revision is called
the planetary model of the atom.
In the planetary model, electrons only exist in certain allowed orbits. Each orbit has a specific
quantity of energy associated with it. As a result, electron orbits are sometimes called energy
levels. Electrons can jump from and to different energy levels within an atom. As they jump
from higher energy levels back down to lower energy levels, they emit light energy. The
colours of light emitted by the excited hydrogen atoms correspond to the changes in energy
that the electrons experience as they move between energy levels. Since he observed only
certain colours, Bohr suggested that an atom has only certain specific energy levels.
Energy Level: a theoretical sphere around an atom where electrons exist; electron
orbit.
