John Dalton was an English scientist born in 1766 who is considered the founder of modern atomic theory. He proposed that all matter is composed of small indivisible particles called atoms and that different atoms have different weights. His atomic theory included the ideas that atoms of a given element are all identical, atoms cannot be created, destroyed, or divided, and atoms combine in simple whole number ratios to form chemical compounds. Dalton's atomic theory was groundbreaking and laid the foundation for modern chemistry, though some of his specific assumptions, like his rule of simplest composition, were later found to be incorrect. He made many contributions in the fields of mathematics, meteorology, and gas behavior.

1. John Dalton
Born
6 September 1766
Eaglesfield, Cumberland,
England
Died
27 July 1844 (aged 77)
Manchester, England
Notable students
James Prescott Joule
Known for
Atomic Theory, Law of
Multiple
Proportions, Dalton's Law
of Partial
Pressures, Daltonism
Influences John Gough
Signature
John dalton

2. Early life
John Dalton was born into a Quaker family
at Eaglesfield in Cumberland, England. The son of a weaver, he joined his older
brother Jonathan at age 15 in running a Quaker school in nearbyKendal.
Around 1790 Dalton seems to have considered taking up law or medicine, but
his projects were not met with encouragement from his relatives —
Dissenters were barred from attending or teaching at English universities —
and he remained at Kendal until, in the spring of 1793, he moved
to Manchester. Mainly through John Gough, a blind philosopher
andpolymath from whose informal instruction he owed much of his scientific
knowledge, Dalton was appointed teacher of mathematics and natural
philosophy at the "New College" in Manchester, a Dissenting academy. He
remained in that position until 1800, when the college's worsening financial
situation led him to resign his post and begin a new career in Manchester as a
private tutor for mathematics and natural philosophy.

3. Five main points of Dalton's atomic theory
1.The atoms of a given element are different from those of any other element; the atoms of different elements
can be distinguished from one another by their respective relative atomic weights.
2.All atoms of a given element are identical.
3.Atoms of one element can combine with atoms of other elements to form chemical compounds; a given
compound always has the same relative numbers of types of atoms.
4.Atoms cannot be created, divided into smaller particles, nor destroyed in the chemical process; a chemical
reaction simply changes the way atoms are grouped together.
5.Elements are made of tiny particles called atoms.
Dalton proposed an additional "rule of greatest simplicity" that created controversy, since it could not be
independently confirmed.
When atoms combine in only one ratio, "..it must be presumed to be a binary one, unless some cause appear to
the contrary".
This was merely an assumption, derived from faith in the simplicity of nature. No evidence was then available to
scientists to deduce how many atoms of each element combine to form compound molecules. But this or some
other such rule was absolutely necessary to any incipient theory, since one needed an assumed molecular
formula in order to calculate relative atomic weights. In any case, Dalton's "rule of greatest simplicity" caused
him to assume that the formula for water was OH and ammonia was NH, quite different from our modern
understanding.
Despite the uncertainty at the heart of Dalton's atomic theory, the principles of the theory survived. To be sure,
the conviction that atoms cannot be subdivided, created, or destroyed into smaller particles when they are
combined, separated, or rearranged in chemical reactions is inconsistent with the existence of nuclear
fusion and nuclear fission, but such processes are nuclear reactions and not chemical reactions. In addition, the
idea that all atoms of a given element are identical in their physical and chemical properties is not precisely true,
as we now know that different isotopes of an element have slightly varying weights. However, Dalton had
created a theory of immense power and importance. Indeed, Dalton's innovation was fully as important for the
future of the science as Antoine Laurent Lavoisier's oxygen-based chemistry had been.

4. unified atomic mass unit
Unit system: SI recognized unit
Unit of... mass
Symbol: u
Unit conversions
1 u in... is equal to...
dalton 1
kendrick 0.99888
kg 1.660 538 782(83) × 10
−27
eV/c
2
931.494 028(23) × 10
6

5. Atomic mass unit
The unified atomic mass unit (symbol: u), also called the dalton (symbol: Da), is
a unitused for indicating mass on an atomic or molecular scale. It is defined as one
twelfth of the rest mass of an unbound atom of carbon-12 in its nuclear and
electronic ground state. The CIPM have categorised it as a "non-SI unit whose values
in SI units must be obtained experimentally".[1]
It’s value
of 1.660538782(83)×10
−27 kg.

6. Jöns Jacob Berzelius
J. J. Berzelius
Born
20 August 1779
Väversunda, Östergötland,
Sweden
Died
7 August 1848 (aged 68)
Stockholm, Sweden
Nationality Sweden
Fields Chemistry
Institutions Karolinska Institute
Alma mater Uppsala University
Doctoral advisor Johann Afzelius
Doctoral students
James Finlay Weir Johnston
Heinrich Rose
Known for
Law of constant
proportions
Chemical notation
Silicon
Selenium
Thorium
Cerium
Notable awards Copley medal
Biography
Berzelius was born at Väversunda
in Östergötland in Sweden. He lost both his
parents at an early age. He was taken care of by
relatives in Linköping where he attended the
school today known as Katedralskolan. Thereafter
he enrolled at the Uppsala University where he
learned the profession of medical doctor from 1796
to 1801. He was taught chemistry byAnders
Gustaf Ekeberg, the discoverer of tantalum. He
worked as apprentice in a pharmacy and with a
physician in the Medevi mineral springs. During
this time he conducted analysis of the spring
water. For his medical studies he examined the
influence of galvanic current on several diseases
and graduated as M.D. in 1802. He worked as
physician near Stockholm until the mine
owner Wilhelm Hisinger discovered his analytical
abilities and provided him with a laboratory.

7. In 1807 Berzelius was appointed professor in chemistry and pharmacy at the Karolinska Institute.
In 1808, he was elected a member of the Royal Swedish Academy of Sciences. At this time, the
Academy had been stagnating for a number of years, since the era ofromanticism in Sweden had
led to less interest in the sciences. In 1818, Berzelius was elected the Academy's secretary, and held
the post until 1848. During Berzelius' tenure, he is credited with revitalising the Academy and
bringing it into a second golden era, the first being the astronomer Pehr Wilhelm Wargentin's
period as secretary (1749-1783). In 1837, he was also elected a member of the Swedish Academy, on
chair number 5.
Discovery of elements
A polycrystalline siliconrod made by the Siemens process
Berzelius is credited with identifying the chemical elements silicon, selenium, thorium, and cerium.
Students working in Berzelius's laboratory also discovered lithium, and vanadium.
New chemical terms
Daguerreotype of Berzelius.
Berzelius is also credited with originating the chemical terms "catalysis", "polymer",
"isomer" and "allotrope", although his original definitions differ dramatically from
modern usage. For example, he coined the term "polymer" in 1833 to describe
organic compounds which shared identical empirical formulas but differed in overall
molecular weight, the larger of the compounds being described as "polymers" of the
smallest. According to this (now obsolete) definition, glucose(C6H12O6) would be a
polymer of formaldehyde (CH2O).

8. Family
Statue of Berzelius in the center ofBerzelii Park, Stockholm
In 1818 Berzelius was ennobled by King Carl XIV Johan; in
1835, at the age of 56, he married Elisabeth Poppius, the 24-
year old daughter of a Swedish cabinet minister, and in the
same year was elevated to friherre.[3]
Berzeliusskolan, a school situated next to his alma mater,
Katedralskolan, is named for him. In 1939 his portrait
appeared on a series of postage stamps commemorating the
bicentenary of the founding of the Swedish Academy of
Sciences.
He died on 7 August 1848 at his home in Stockholm, where
he had lived since 1806..[4]
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more
different chemical elements[1][2][3] that can be separated into simpler substances
by chemical reactions.[4] Chemical compounds have a unique and defined chemical
structure; they consist of a fixed ratio of atoms[3] that are held together in a defined
spatial arrangement by chemical bonds. Chemical compounds can
be molecularcompounds held together by covalent bonds, salts held together by ionic
bonds, intermetallic compounds held together by metallic bonds, orcomplexes held
together by coordinate covalent bonds. Pure chemical elements are not considered
chemical compounds, even if they consist of molecules which contain only multiple
atoms of a single element (such as H2, S8, etc.),[5] which are called diatomic
molecules orpolyatomic molecules.

9. Elementary concepts
Characteristic properties of compounds:
1. Elements in a compound are present in a definite proportion
Example- 2 atoms of hydrogen + 1 atom of oxygen becomes 1 molecule of compound-water.
2. Compounds have a definite set of properties
Elements of the compound do not retain their original properties.
Example- Hydrogen(element{which is combustible and non-supporter of combustion}) + Oxygen(element{which
is non-combustible and supporter of combustion}) becomes Water(compound{which is non-combustible and non-
supporter of combustion})
3. Elements in a compound cannot be separated by physical methods.
Valency is the number of hydrogen atoms which can combine with one atom of the element forming a
compound.
Formula
Chemists describe compounds using formulas in various formats. For compounds that exist
as molecules, the formula for the molecular unit is shown. For polymeric materials, such
as minerals and many metal oxides, the empirical formula is normally given, e.g. NaCl
for table salt.
The elements in a chemical formula are normally listed in a specific order, called the Hill
system. In this system, the carbon atoms (if there are any) are usually listed first, any
hydrogen atoms are listed next, and all other elements follow in alphabetical order. If the
formula contains no carbon, then all of the elements, including hydrogen, are listed
alphabetically. There are, however, several important exceptions to the normal rules. For
ionic compounds, the positive ion is almost always listed first and the negative ion is listed
second. For oxides, oxygen is usually listed last.

10. Chemical structure
A chemical structure includes molecular geometry, electronic structure and crystal
structure of molecules. Molecular geometry refers to the spatial arrangement of atoms in
a molecule and the chemical bonds that hold the atoms together. Molecular geometry can range
from the very simple, such as diatomic oxygen or nitrogen molecules, to the very complex, such
as protein or DNA molecules. Molecular geometry can be roughly represented using
a structural formula. Electronic structure describes the occupation of a molecule's molecular
orbitals.
Ions
For ions, the charge on a particular atom may be denoted with a right-hand superscript. For
example Na+, or Cu2+. The total charge on a charged molecule or a polyatomic ion may also be
shown in this way. For example: hydronium, H3O+ or sulfate, SO4
2−.
For more complex ions, brackets [ ] are often used to enclose the ionic formula, as in [B12H12]2−,
which is found in compounds such asCs2[B12H12]. Parentheses ( ) can be nested inside brackets to
indicate a repeating unit, as in [Co(NH3)6]3+. Here (NH3)6 indicates that the ion contains
six NH3 groups, and [ ] encloses the entire formula of the ion with charge +3.
Isotopes
Although isotopes are more relevant to nuclear chemistry or stable isotope chemistry than to
conventional chemistry, different isotopes may be indicated with a left-hand superscript in a
chemical formula. For example, the phosphate ion containing radioactive phosphorus-32 is32PO4
3-.
Also a study involving stable isotope ratios might include the molecule 18O16O.
A left-hand subscript is sometimes used redundantly to indicate the atomic number. For
example, 8O2 for dioxygen, and 16
8O2 for the most abundant isotopic species of dioxygen. This is
convenient when writing equations for nuclear reactions, in order to show the balance of charge
more clearly.

11. Isobutane
Molecular formula:
C4H10
Semi-structural
formula: (CH3)3CH
Butane
Molecular formula:
C4H10
Semi-structural
formula:
CH3CH2CH2CH3
Chemical symbol
A chemical symbol is a 1- or 2-letter
internationally agreed code for a chemical
element, usually derived from the name of the
element, often in Latin. The first letter, only, is
capitalised. For example, "He" is the symbol
for helium (English name, not known
in ancient Roman times), "Pb"
for lead (plumbum in Latin), "W"
for tungsten (wolfram in German, not known
in Roman times). Temporary
symbols assigned to newly or not-yet
synthesized elements use 3-letter symbols.
For example, "Uno" was the temporary
symbol for Hassium which had the
temporary name of Unniloctium.
Chemical symbols may be modified by
the use of superscripts or subscripts to
specify a particular isotope of an atom.
Additionally superscripts may be used
to indicate the ionization or oxidation
state of an element.
Attached subscripts or superscripts specifying a
nucleotide or molecule have the following
meanings and positions:
The nucleon number (mass number) is shown in
the left superscript position (e.g., 14N)
The proton number (atomic number) may be
indicated in the left subscript position
(e.g., 64Gd)
If necessary, a state of ionization or an excited
state may be indicated in the right superscript
position (e.g., state of ionization Ca2+).
Inastronomy, non-ionised atomic hydrogen is
often known as "HI", and ionised hydrogen as
"HII".[1]
The number of atoms of an element in
a molecule or chemical compound is shown in
the right subscript position (e.g., N2 or Fe2O3)
A radical is indicated by a dot on the right side
(e.g., Cl· for a chloride radical)