Download Chemistry Review: Antoine Lavoisier (1743

Chemistry Review:
 Antoine Lavoisier (1743-94) defined the term “element” and identified 23
known substances as elements. He based his investigations on careful
measurements of mass in chemical reactions.
 Allessandro Volta (1745-1827) invented the voltaic pile, now known as a
battery. It provided scientists with a source of electricity for their
investigations.
 Humphry Davy (1778-1829) used electrolysis to decompose compounds and
identified many metallic elements.
 Michael Faraday (1791-1867) worked with Davy and coined the term
“electrolysis”
 Joseph Proust (1754-1826) decomposed various compounds into elements
and measured the mass of the elements produced. The patterns he
discovered led to the law of definite proportions.
 John Dalton (1766-1844) proposed the first atomic theory. His theory
extended the particle theory to provide a model for the properties of
elements in terms of their atoms, and the formation of compounds.
 Sir Francis Bacon (1561-1626) used the scientific method to carry out
investigations. He was one of the first scientists to develop new
knowledge as a result of experimentation.
 Robert Boyle (1627-1691) believed that the Greek philosophers’ fourelement theory (earth, air, fire and water) could be improved upon, and he
helped to lay the foundation for the concept of elements and compounds.
 Ernest Rutherford Carried out his experiment in 1919 with alpha particles
scattering, identified the “proton” as an elementary particle.
Density = mass ÷ volume
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(Flow chart): pure substances can be elements and compounds, which
are made up of atoms (which cannot be created or destroyed
chemically), which make up molecules. (which can be created or
destroyed chemically)
Molecule (latin: molecula) means “little mass”
Parts of the Atom: proton found in the nucleus (+ charge), neutron
found in the nucleus (neutral) and the electron in motion around the
nucleus (- charge)
Bohr-Rutherford model: both Bohr and Rutherford made important
contributions to the structure of the atom. Their model is used today
as an introduction to studying chemistry.
Definitions:
 Isotopes: atoms of the same element that differs in mass. Ex
there are 3 isotopes of hydrogen, with mass numbers of 1, 2
and 3. These atoms have different masses because they have
different numbers of neutrons. However, since they have the
same number of protons, they are the same element. Most
elements have more than 1 naturally occurring isotope.
However, the relative abundance of the isotopes follows no
patterns. For example, 99.98% of all hydrogen atoms have a
mass number of 1 (H-1), less than 0.02% are H-2, and even less
are H-3!
 Properties of isotopes: Since all isotopes of an element have
the same number of electrons, their chemical properties will be
exactly the same. However, they have different masses due to
the different number of neutrons; therefore, they will have
slightly different properties that relate to mass. (Ex. Density ,
melting and boiling point). Also. Since the neutron/proton ratio
is different for isotopes of an element, some may be
radioactive while others are stable.
 Atomic masses: The atomic masses listed on the periodic table
take into account the number and abundance of all naturally
occurring isotopes of each element and are a weighted average
of the atomic masses. Carbon-12 is the only isotope for which
the atomic mass is a rounded number.
 Atomic Number: Is the number of electrons or protons in an
atom. The number of neutrons is determined by subtracting
the atomic number from the mass number of the element. The
elements in the periodic table are arranged in increasing atomic
number.
 Atomic Mass: Is the mass of an atom of an element, often
expressed in atomic mass units. (u) The elements are arranged
on the periodic table in order of increasing atomic number.
 Periodic Table: Elements are arranged in order of increasing
atomic number.
 Groups/Families: are the vertical rows, each member has
similar chemical and physical properties. There is an
extra shell/energy level of electrons as you go down the
rows/period. Each element has the same number of
electrons in the outer shell. (Except He, which is full with
2 electrons and the heavier elements)
 Periods: are the horizontal rows, as you go to the right
each successive element has one more electron in the
outer shell/energy level. Once the outer shell is “full” the
next electron must go into a new outer shell.
Bonding:
 Ionic bonding: electrons are transferred from one
atom to another. This requires the formation of
ions which creates a positive or negative charge.
(All atoms are neutral to begin with because they
contain the same number of electrons (-) and
protons (+). Once this change occurs the atom is
going to be “attracted to the opposite”!
Ex. When fluorine atoms gain 1 electron from sodium
it becomes negative (F-) and is ready to bond with a
now positive sodium(Na+).
 Covalent bonding: 2 or more atoms “share”
electrons.