he made water by burning hydrogen
in oxygen (see cavendish, henry). He
also devised a rational nomenclature
for chemical compounds. In 1794 he
was tried by the Jacobins as an opponent of the Revolution (because of
his tax-gathering), found guilty, and
guillotined.
law of chemical equilibrium See
equilibrium constant.
law of conservation of energy
See conservation law.
law of conservation of mass See
conservation law.
law of constant composition See
chemical combination.
law of deÜnite proportions See
chemical combination.
law of mass action See mass action.
law of multiple proportions See
chemical combination.
law of octaves (Newlands’ law)
An attempt at classifying elements
made by John Newlands (1837–98) in
1863. He arranged 56 elements in
order of increasing atomic mass in
groups of eight, pointing out that
each element resembled the element
eight places from it in the list. He
drew an analogy with the notes of a
musical scale. Newlands’ octaves
were groups of similar elements distinguished in this way: e.g. oxygen
and sulphur; nitrogen and phosphorus; and Ûuorine, chlorine, bromine,
and iodine. In some cases it was necessary to put two elements in the
same position. The proposal was rejected at the time. See periodic table.
A
• John Newlands’ paper
law of reciprocal proportions
See chemical combination.
lawrencium Symbol Lr. A radioactive metallic transuranic element
belonging to the *actinoids; a.n. 103;
mass number of the Ürst discovered
isotope 257 (half-life 8 seconds). A
number of very short-lived isotopes
have now been synthesized. The element was identiÜed by Albert
Ghiorso and associates in 1961. It
was named after E. O. Lawrence
(1901–58).
A
• Information from the WebElements site
laws of chemical combination
See chemical combination.
laws, theories, and hypotheses
In science, a law is a descriptive principle of nature that holds in all circumstances covered by the wording
of the law. There are no loopholes in
the laws of nature and any exceptional event that did not comply with
the law would require the existing
law to be discarded or would have to
be described as a miracle. Eponymous laws are named after their discoverers (e.g. *Boyle’s law); some
laws, however, are known by their
subject matter (e.g. the law of conservation of mass), while other laws use
both the name of the discoverer and
the subject matter to describe them
(e.g. Newton’s law of gravitation).
A description of nature that encompasses more than one law but
has not achieved the uncontrovertible status of a law is sometimes
called a theory. Theories are often
both eponymous and descriptive of
the subject matter (e.g. Einstein’s
theory of relativity and Darwin’s
theory of evolution).
A hypothesis is a theory or law that
retains the suggestion that it may not
be universally true. However, some
hypotheses about which no doubt
still lingers have remained hypotheses (e.g. Avogadro’s hypothesis), for
no clear reason. Clearly there is a de319
laws, theories, and hypotheses
l
www.AzShimi.ir www.AzShimi.com
in oxygen (see cavendish, henry). He
also devised a rational nomenclature
for chemical compounds. In 1794 he
was tried by the Jacobins as an opponent of the Revolution (because of
his tax-gathering), found guilty, and
guillotined.
law of chemical equilibrium See
equilibrium constant.
law of conservation of energy
See conservation law.
law of conservation of mass See
conservation law.
law of constant composition See
chemical combination.
law of deÜnite proportions See
chemical combination.
law of mass action See mass action.
law of multiple proportions See
chemical combination.
law of octaves (Newlands’ law)
An attempt at classifying elements
made by John Newlands (1837–98) in
1863. He arranged 56 elements in
order of increasing atomic mass in
groups of eight, pointing out that
each element resembled the element
eight places from it in the list. He
drew an analogy with the notes of a
musical scale. Newlands’ octaves
were groups of similar elements distinguished in this way: e.g. oxygen
and sulphur; nitrogen and phosphorus; and Ûuorine, chlorine, bromine,
and iodine. In some cases it was necessary to put two elements in the
same position. The proposal was rejected at the time. See periodic table.
A
• John Newlands’ paper
law of reciprocal proportions
See chemical combination.
lawrencium Symbol Lr. A radioactive metallic transuranic element
belonging to the *actinoids; a.n. 103;
mass number of the Ürst discovered
isotope 257 (half-life 8 seconds). A
number of very short-lived isotopes
have now been synthesized. The element was identiÜed by Albert
Ghiorso and associates in 1961. It
was named after E. O. Lawrence
(1901–58).
A
• Information from the WebElements site
laws of chemical combination
See chemical combination.
laws, theories, and hypotheses
In science, a law is a descriptive principle of nature that holds in all circumstances covered by the wording
of the law. There are no loopholes in
the laws of nature and any exceptional event that did not comply with
the law would require the existing
law to be discarded or would have to
be described as a miracle. Eponymous laws are named after their discoverers (e.g. *Boyle’s law); some
laws, however, are known by their
subject matter (e.g. the law of conservation of mass), while other laws use
both the name of the discoverer and
the subject matter to describe them
(e.g. Newton’s law of gravitation).
A description of nature that encompasses more than one law but
has not achieved the uncontrovertible status of a law is sometimes
called a theory. Theories are often
both eponymous and descriptive of
the subject matter (e.g. Einstein’s
theory of relativity and Darwin’s
theory of evolution).
A hypothesis is a theory or law that
retains the suggestion that it may not
be universally true. However, some
hypotheses about which no doubt
still lingers have remained hypotheses (e.g. Avogadro’s hypothesis), for
no clear reason. Clearly there is a de319
laws, theories, and hypotheses
l
www.AzShimi.ir www.AzShimi.com