At the end of the lesson, you will have to: 1. cite the contribution of John Dalton toward the understanding of the concept of the chemical elements 2. explain how Dalton’s theory contributed to the discovery of other elements.

1. LESSON 5:

2. • He recognized elements as the
simplest substances that constitute
mixtures, and that elements are
those that cannot be decomposed
into other substances via chemical
reactions.
• He emphasized the need to observe
and test the presence of corpuscles
in alchemical experiments.
ROBERT BOYLE

3. ROBERT BOYLE
• Had the idea of:
Corpuscles
 “certain primitive and simple, or
perfectly unmingled bodies” that
were indivisible and whole.

4. Antoine Lavoisier
• Father of Modern
Chemistry
• He opposed the
Phlogiston Theory (a
superseded scientific theory
that postulated that a fire-like
element called phlogiston is
contained within combustible
bodies and released during
combustion)

5. Antoine Lavoisier
 Defined CHEMICAL ELEMENT (substance that
cannot be broken down into simpler components.)
 Defined COMPOUND (a substance composed of
these elements.)
 Made an initial list of 33 elements, and
created a systematic way of naming elements
and the compounds they created.
 He also wrote the first Chemistry textbook.

6. JOHN DALTON
• His Chemical Atomic
Theory merged the
concepts of the atom and
element

7. • Gases, and all chemically inseparable
elements, are made of atoms.
• The atoms of an element are identical in their
masses.
• Atoms of different elements have different
masses.
• Atoms combine in small, whole number
ratios.
Chemical atomic theory

8. •Antoine Lavoisier’s Law of
Conservation of Mass
•Joseph Proust’s Law of Definite
Proportions
•John Dalton’s Law of Multiple
Proportions
3 Fundamental laws

9. Antoine Lavoisier’s Law of
Conservation of Mass
mass is neither created nor
destroyed during an ordinary
chemical reaction or physical
reaction.
3 Fundamental laws

10. • Antoine Lavoisier’s Law of
Conservation of Mass
3 Fundamental laws

11. •Joseph Proust’s Law of Definite
Proportions
 chemical compound contains the
same elements in exactly the same
proportions by mass regardless of the
sample of the source of the compound.
3 Fundamental laws

12. • Joseph
Proust’s
Law of
Definite
Proportions
3 Fundamental laws

13. •John Dalton’s Law of Multiple
Proportions
 if two or more different compounds are
composed of the same two elements, then
the ratios of the masses of the second
element, combined with a certain mass of
the first element is always a ratio of small
whole numbers
3 Fundamental laws

14. • John
Dalton’s
Law of
Multiple
Proportions
3 Fundamental laws

15. • that elements were made of the same atoms and had
properties unique to the element, while chemical
compounds were made of different combined or
compounded atoms, and exhibited different sets of
properties.
• that one could compute the weights of elements (and their
atoms) by looking at comparable amounts of the
compounds they formed.
• that one could compute atomic weights compared to a
reference.
Dalton’s Chemical Atomic Theory

16. Joseph Gay-Lussac
He determined that oxygen
gas was made of 2 atoms
of oxygen and took the
form of a molecule instead
of an atom. This offered the
possibility that an element wasn’t
necessarily made up of one atom,
thus distinguishing the atom from
the molecule.

17. Amedeo Avogadro
He figured out a reliable
way of weighing atoms and
molecules. (MOLE)
He determined that equivalent
volumes of two gases under similar
conditions contained equal numbers
of particles, and that differences in
their masses was a result of a
difference in their molecular mass.

18. He published a periodic
table of elements that
ordered elements
according to their atomic
weights. He noted patterns in their
properties that enabled him to predict
the discovery of other elements. His
table became the basis of the
modern Periodic Table.
Dmitri Mendeleev