Download Models of the Atom and Periodic Trends Worksheet

Models of the Atom and Periodic Trends
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John Dalton proposed that all matter is made up of tiny
particles. These particles are molecules or atoms.
Molecules can be broken down into atoms by chemical
processes. Atoms cannot be broken down by chemical or
physical processes.
According to the law of definite composition, the mass
ratio of carbon to oxygen in carbon dioxide was always the
same. Carbon dioxide was composed 1 carbon atom and 2
oxygen atoms.
The first two parts of Dalton’s theory were later proven
incorrect. Proposals 3, 4, and 5 are still accepted today.
About 50 years after Dalton’s proposal, evidence was seen
that atoms were divisible.
Two subatomic particles were discovered. Negatively
charged electrons, e–. Positively charge protons, p+. An
electron has a relative charge of -1 and a proton has a
relative charge of +1.
J.J. Thomson proposed a subatomic model of the atom in
1903. Originally, Thomson could only calculate the massto-charge ration of a proton and an electron. Thomson
calculated the masses of a proton and electron. An
electron has a mass of 9.11 × 10-28 g. A proton has a mass
of 1.67 × 10-24 g
Robert Millikan determined the charge of an electron in
1911.
There are three types of radiation: Alpha (α), Beta (β), &
Gamma (γ); Alpha rays are composed of helium atoms
stripped of their electrons (helium nuclei). Beta rays are
composed of electrons. Gamma rays are high energy
electromagnetic radiation.
Rutherford fired alpha particles at thin gold foils. If the
“plum pudding” model of the atom was correct, most αparticles should pass through undeflected. Most of the
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alpha particles passed through the foil because an atom is
largely empty space.
At the center of an atom is the atomic nucleus which
contains the atom’s protons.
Rutherford proposed a new model of the atom: The
negatively charges electrons are distributed around a
positively charged nucleus.
Based on the heaviness of the nucleus, Rutherford
predicted that is must contain neutral particles in addition
to protons. Neutrons, n0, were discovered about 30 years
later. A neutron is about the size of a proton without any
charge.
Each element has a characteristic number of protons in
the nucleus. This is the atomic number, Z.
The total number of protons and neutrons in the nucleus of
an atom is the mass number, A.
We use atomic notation to display the number of protons
and neutrons in the nucleus of an atom:
The element is sodium (symbol Na). The atomic number is
11 – sodium has 11 protons. The mass number is 23. The
number is neutrons is 12.
Atoms of the same element that have a different number
of neutrons in the nucleus are called isotopes. All atoms of
the same element have the same number of protons. Most
elements occur naturally with varying numbers of neutrons.
Isotopes have the same atomic number but different mass
numbers.
How many protons and neutrons does an atom of mercury202 have?
Copper has two isotopes: 63Cu with a mass of 62.930 amu
and 69.09% abundance 65Cu with a mass of 64.928 amu and
30.91% abundance The average atomic mass of copper is?
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Light travels through space as a wave, similar to an ocean
wave.
Wavelength is the distance light travels in one cycle.
Frequency is the number of wave cycles completed each
second.
Light has a constant speed: 3.00 × 108 m/s.
The longer the wavelength of light, the lower the
frequency. The shorter the wavelength of light, the higher
the frequency.
The visible spectrum is the range of wavelengths between
400 and 700 nm. Radiant energy that has a wavelength
lower than 400 nm and greater than 700 nm cannot be
seen by the human eye.
The complete radiant energy spectrum is an
uninterrupted band, or continuous spectrum.
In 1900, Max Planck proposed that radiant energy is not
continuous, but is emitted in small bundles. This is the
quantum concept.
Radiant energy has both a wave nature and a particle
nature.
Niels Bohr speculated that electrons orbit about the
nucleus in fixed energy levels.
When an electrical voltage is passed across a gas in a
sealed tube, a series of narrow lines is seen. These lines
are the emission line spectrum.
The emission line spectrum of each element is unique.
It was later shown that electrons occupy energy sublevels
within each level. These sublevels are given the
designations s, p, d, and f.
The first energy level has 1 sublevel: 1s
The second energy level has 2 sublevels: 2s and 2p
The third energy level has 3 sublevels: 3s, 3p, and 3d
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The maximum number of electrons in each of the energy
sublevel depends on the sublevel: The s sublevel holds a
maximum of 2 electrons. The p sublevel holds a maximum
of 6 electrons. The d sublevel holds a maximum of 10
electrons. The f sublevel holds a maximum of 14 electrons.
39. Electrons are arranged about the nucleus in a regular
manner. The first electrons fill the energy sublevel
closest to the nucleus. Electrons continue filling each
sublevel until it is full and start filling the next closest
sublevel.
40. A partial list of sublevels in order of increasing energy is:
1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d …
41. The electron configuration of an atom is a shorthand
method of writing the location of electrons by sublevel.
42. The sublevel is written followed by a superscript with the
number of electrons in the sublevel. If the 2p sublevel
contains 2 electrons, it is written 2p2
43. The electron configuration of Fe: 1s2 2s2 2p6 3s2 3p6
4s2 3d 6
44. In the quantum mechanical atom, orbitals are arranged
according to their size and shape.
45. The higher the energy of an orbital, the larger its size.
46. Recall that there are three different p sublevels. porbitals have a dumbbell shape. Each of the p-orbitals has
the same shape, but each is oriented along a different axis
in space.
47. Atoms are composed of protons, neutrons, and electrons.
48. The protons and neutrons are located in the nucleus and
the electrons are outside the nucleus. Atoms are mostly
empty space.
49. The number of protons is referred to as the atomic
number for the atom.
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All atoms of the same element have the same number of
protons.
Isotopes are atoms with the same number of protons but
differing numbers of neutrons.
The mass number for an isotope is the total number of
protons plus neutrons.
The atomic mass of and elements is the weighted average
of the masses of all the naturally occuring isotopes.
Light has both properties of both waves and particles.
The particles of light are referred to as photons.
The energy of photons is quantized.
Electrons exist around the nucleus of atoms in discrete,
quantized energy levels.
Electrons fill energy sublevels starting with the lowest
energy sublevel and filling each successive level of higher
energy.
J. A. R. Newlands suggested that the 62 known elements
be arranged into groups of seven according to increasing
atomic mass in 1865. His theory was the law of octaves
Mendeleev proposed that the properties of the chemical
elements repeat at regular intervals when arranged in
order of increasing atomic mass.
H. G. J. Moseley discovered that the nuclear charge
increased by one for each element on the periodic table.
The periodic law states that the properties of elements
recur in a repeating pattern when arranged according to
increasing atomic number.
With the introduction of the concept of electron energy
levels by Niels Bohr, the periodic table took its current
arrangement.
A vertical column on the periodic table is a group or family
of elements.
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A horizontal row on the periodic table is a period or series
of elements.
There are 18 groups and 7 periods on the periodic table.
The first period has only 2 elements, H and He.
The second and third periods have 8 elements
each: Li through Ne and Na through Ar. The fourth
and fifth periods each have 18 elements: K through Kr
and Rb through Xe
Hydrogen occupies a special position on the periodic table.
It is a gas with properties similar to nonmetals. It also
reacts by losing one electron, similar to metals.
There are several groupings of elements.
The representative elements or main-group elements, are
in the A groups (groups 1, 2, and 12 – 18).
The transition elements are in the B groups (groups 3 –
12).
The inner transition elements are found below the
periodic table. They are also referred to as the rare
earth elements.
The inner transition elements are divided into the
lanthanide series and the actinide series.
Several columns of the periodic table have common, trivial
names. Group IA/1 are the alkali metals . Group IIA/2
are the alkaline earth metals
The arrangement of the periodic table means that the
physical properties of the elements follow a regular
pattern.
We can look at the size of atoms, or their atomic radius.
There are two trends for atomic radius: Atomic radius
decreases as you go up a group. Atomic radius decreases
as you go left to right across a period.
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Atoms get smaller as you go bottom to top on the periodic
table because as you travel up a group, there are fewer
energy levels on the atom.
Atomic radius decreases as you travel left to right across
the periodic table because the number of protons in the
nucleus increases.
As the number of protons increases, the nucleus pulls the
electrons closer and reduces the size of the atom.
Metallic character is the degree of metal character of an
element.
Members of a family also have similar chemical properties.
All of the alkali metals have oxides of the general formula
M2O: Li2O, Na2O, K2O, Rb2O, Cs2O, and Fr2O.
The formula for the chloride of calcium is CaCl2. What is
the formula for the chloride of barium? BaCl2.
We can break the periodic table into blocks of elements
where certain sublevels are being filled: Groups IA/1 and
IIA/2 are filling s sublevels, so they are called the s block
of elements. Groups IIIB/3 through IIB/12 are filling d
sublevels, so they are called the d block of elements.
Recall, the electron configuration for Na is: Na: 1s2 2s2
2p6 3s1 or [Ne] 3s1.
We can abbreviate the electron configuration by indicating
the innermost electrons with the symbol of the preceding
noble gas.
When an atom undergoes a chemical reaction, only the
outermost electrons are involved.
These electrons are of the highest energy and are
furthest away from the nucleus. These are the valence
electrons.
The valence electrons are the s and p electrons beyond
the noble gas core.
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The Roman numeral in the American convention indicates
the number of valence electrons. Group IA elements have
1 valence electron. Group VA elements have 5 valence
electrons
When using the IUPAC designations for group numbers,
the last digit indicates the number of valence electrons.
Group 14 elements have 4 valence electrons. Group 2
elements have 2 valence electrons .
An electron dot formula of an elements shows the symbol
of the element surrounded by its valence electrons.
The ionization energy of an atom is the amount of energy
required to remove an electron in the gaseous state.
In general, the ionization energy increases as you go from
the bottom to the top in a group. In general, the ionization
energy increases as you go from left to right across a
period of elements.
The closer the electron to the nucleus, the more energy is
required to remove the electron.
Recall, that metals tend to lose electrons and nonmetals
tend to gain electrons.
Metals lose their valence electrons to form ions.
Group IA/1 metals form 1+ ions, group IIA/2 metals form
2+ ions, group IIIA/13 metals form 3+ ions, and group
IVA/14 metals from 4+ ions.
By losing their valence electrons, the achieve a noble gas
configuration.
Similarly, nonmetals can gain electrons to achieve a noble
gas configuration.
Group VA/15 elements form -3 ions, group VIA/16
elements form -2 ions, and group VIIA/17 elements form
-1 ions.
When we write the electron configuration of a positive ion,
we remove one electron for each positive charge:
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Models of the Atom and Periodic Trends
105. When we write the electron configuration of a negative
ion, we add one electron for each negative charge.
106. The elements in the periodic table are arranged by
increasing atomic number.
107. The elements have, regular repeating chemical and
physical properties.
108. The periodic table can be broken down into groups or
families which are columns and periods or series which are
rows
109. Atomic radius and metallic character increase as you go
from bottom to top and from left to right across the
periodic table.
110. The periodic table can be broken down into blocks where a
certain sublevel is being filled.
111. Valence electrons are the outermost electrons and are
involved in chemical reactions.
112. We can write electron dot formulas for elements which
indicate the number of valence electrons.
113. Ionization energy is the amount of energy that is required
to remove an electron from an atom in the gaseous state.
114. We can predict the charge on the ion of an element from
its position on the periodic table.
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