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Transcript
II. Periodic Table
The placement or location of
elements on the Periodic Table
gives an indication of physical
and chemical properties of that
element. The elements on the
Periodic Table are arranged in
order of increasing atomic
number.
Mendeleev’s original table was according to mass. This was
changed when Moseley discovered atomic number.
J Deutsch 2003
2
The number of protons in an
atom (atomic number) identifies the
Atomic number is written
element. 6C on the bottom left.
The sum of the protons and
neutrons in an atom (mass number)
identifies an isotope.Common
notations that represent
isotopes include: 14C, carbonMass number is written on
14, C-14.
the upper left.
J Deutsch 2003
3
The average atomic mass of
an element is the weighted
average of the masses of its
naturally occurring isotopes.
Isotope Mass Abundance
Calculation
12C
12
98.89%
12 x .9889 =
13C
13
1.108%
13 x 0.01108 = 0.1440
Atomic Mass (weighted average)
J Deutsch 2003
11.87
12.01 amu
4
Regents Question: 01/03 #9
An atom of carbon-12 and an atom of carbon-14 differ in
(1) Atomic number
(2) Atomic mass
(3) Nuclear charge
(4) Number of electrons
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Regents Question: 06/02 #4
All the isotopes of a given atom have
(1) the same mass number and same atomic number
(2) the same mass number but different atomic numbers
(3) different mass numbers but the same atomic number
(4) different mass numbers and different atomic number
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Regents Question: 06/02 #9
Atoms of the same element that have different numbers
of neutrons are classified as
(1) Charged atoms
(2) Charged nuclei
(3) Isomers
(4) Isotopes
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Atomic mass is found on the
Periodic Table of the Elements
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Regents Question: 01/03 #36
Hydrogen has three isotopes with mass numbers of 1, 2,
and 3 and has an average atomic mass of 1.00794
amu. This information indicates that
(1) Equal number of each isotope are present
(2) More isotopes have an atomic mass of 2 or 3 than 1
(3) More isotopes have an atomic mass of 1 rather than
2 of 3
(4) Isotopes have only an atomic mass of 1
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Regents Question: 01/03 #3
In which list are the elements arranged in order of
increasing atomic mass?
(1) Cl, K, Ar
(2) Fe, Co, Ni
(3) Te, I Xe
(4) Ne, F, Na
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Elements can be classified by
their properties and located on
the Periodic Table as metals,
nonmetals, metalloids or
semimetals (B, Si, Ge, As, Sb,
Te), and noble gases.
Metals on
the left
J Deutsch 2003
Nonmetals
on the right
Metalloids or
semimetals
11
Comparing the physical properties of
metals and nonmetals
Metals
 Make up 2/3 of the periodic table
 Low ionization energy: amount of energy needed to
remove valence electron Low electronegativity: desire for
more electrons.
 Solid at room temperature except mercury (Hg)
 Good conductors of heat and electricity
 Malleable – can be hammered into shapes (thin sheets)
 Ductile – can be pulled into wires
 Lose electrons to form (+) ions
 Most metallic element is in the lower left corner of the
periodic table. Francium (Fr)
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Comparing the physical properties of
metals and nonmetals
Nonmetals
 Many different states (phases)
Gases: Hydrogen (H), Oxygen (O), Nitrogen (N), Fluorine
(F), Chlorine (Cl), All of group 18 (noble gases)
Helium (He), Neon (Ne) Argon (Ar), Krypton (Kr), Xenon
(Xe), Radon (Rn)
 Bromine (Br) - the only liquid nonmetal at room
temperature
 Poor conductors of heat and electricity and brittle – breaks
when hit
 High ionization and electronegativity.
 Gain electrons to form(-) ions
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Metalloids: having both metallic
and non metallic properties
B(boron), Si(silicon),
Ge(germanium), As(arsenic),
Sb(Antimony), Te(tellurium) and
At(astatine)
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Regents Question: 01/03 # 37
Which list of elements contains two metalloids?
(1) Si, Ge, Po, Pb
(2) As, Bi, Br, Kr
(3) Si, P, S, Cl
(4) Po, Sb, I, Xe
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Regents Question: 06/03 # 6
Which is a property of most nonmetallic solids?
(1) high thermal conductivity
(2) high electrical conductivity
(3) brittleness
(4) malleability
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Elements can be differentiated
by their physical properties.
Physical properties of
substances, such as density,
conductivity, malleability,
solubility, and hardness, differ
among elements.
Density=mass/volume
A physical property is one which does not change the
identity of the substance when tested.
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Elements can be differentiated
by chemical properties.
Chemical properties describe
how an element behaves
during a chemical reaction.
When testing a chemical property, the substance may
change into another substance.
The number of atoms an element combines with is an
important chemical property:
NaCl CaCl2 AlCl3 CCl4
HCl
J Deutsch 2003
H2O
NH3
CH4
18
Some elements exist in two or
more forms in the same
phase. These forms differ in
their molecular or crystal
structure, and hence in their
properties. These are called
allotropes.
J Deutsch 2003
Allotropes of oxygen
Allotropes of carbon
Oxygen ( O2 )
Graphite
Ozone ( O3 )
Diamond
Buckminsterfullerene
19
For Groups 1, 2, and 13-18 on
the Periodic Table, elements
within the same group have
the same number of valence
electrons (helium is an
exception) and therefore
similar chemical properties.
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Regents Question: 06/03 # 53-54
Given: Samples of Na, Ar, As, Rb
Which two of the given elements have the most
similar chemical properties?
Na and Rb
Explain your answer in terms of the Periodic Table
of the Elements.
They are in the same group
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Group numbers and family names
Groups are elements that share similar characteristic
 Group 1
Alkali Metals
– Very reactive metals in water, always found as
compounds in nature
– Francium is the most reactive metal
– 1 valence electron - lose 1 electron to form +1 ions
 Group 2
Alkaline Earth Metals
– Reactive metals, always found as compounds in nature
– 2 valence electrons - lose 2 electron to form +2 ions
 Group 3-12
Transition Metals
– Forms colored solutions
– Fills two valence shells at one time
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Groups continued
 Group 17
Halogens
– Reactive nonmetals
– 7 valence electrons - gain 1 electron to form –1
ions
 Groups 18 Noble Gases
– Not reactive – do not form ions
– Filled, stable valence shell (8 electrons except
He which has 2)
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Regents Question: 01/03 #6
Which Group of the periodic Table contains atoms
with a stable outer electron configuration?
(1) 1
(2) 8
(3) 16
(4) 18
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Regents Question: 02/06 #6
Which element is classified as a noble gas at STP?
(1) Hydrogen
(2) Oxygen
(3) Neon
(4) Nitrogen
STP is standard temperature and pressure
0ºC (273K) and 1 atm (101.3kPa)
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The succession of elements
within the same group
demonstrates characteristic
trends: differences in atomic
radius, first ionization energy,
ionic radius, electronegativity,
metallic/nonmetallic properties.
J Deutsch 2003
Going down a group, there are more shells
separating the nucleus from the valence
electrons
26
The succession of elements
across the same period
demonstrates characteristic
trends: differences in atomic
radius, ionic radius,
electronegativity, first ionization
energy, metallic/nonmetallic
properties.
Going across a period, there are more protons
pulling on the valence electrons
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Reference Table S
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Trends in Atomic Radius
 Atomic Radius – half the distance between
two nuclei or the distance between the
nucleus and outer( valence) electrons
 Going down a group, the atomic radius
increases because there are more principal
energy levels (shells)
 Going across a period, the atomic radius
decreases because there are more protons
pulling the valence shell closer
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Atomic Radius
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Regents Question: 06/03 #38
Which list of elements is arranged in order of
increasing atomic radii?
(1) Li, Be, B, C
(2) Sr, Ca, Mg, Be
(3) Sc, Ti, V, Cr
Check Table S
(4) F, Cl, Br, I
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Forming Ions – making atoms happy
 Atoms gain or lose electrons to complete their
outer shell
– A noble gas configuration
– A complete octet
– 8 electrons
 Metals lose electrons to form positive (+) ions
 Nonmetals gain electrons to form negative (-) ions
 Ionic Radius
– A negative ion is always larger than its original atom.
– A positive ion is always smaller than its original atom.
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Regents Question: 06/03 #37
What is the total number of electrons in a Cu + ion?
(1) 28
(2) 29
(3) 30
(4) 36
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Ionic Radius in Metals
 Sodium (Na) is a metal
– Electron configuration 2-8-1
• (11 protons and 11 electrons)
– Loses 1 electron in its valence shell
– A sodium atom becomes a sodium ion
• Na+
• 2-8 (10 electrons but 11 protons)
– Same electron configuration as a noble gas (Ne)
but has more protons. Electrons are pulled in
much closer so the radius decreases.
 2+ ions are even smaller than + ions
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Ionic Radius in Nonmetals
 Chlorine (Cl) is a nonmetal
– Electron configuration 2-8-7
Notice-name of
negative ions end
in IDE
• (17 protons and 17 electrons)
– Gains 1 electron in its valence shell
– A chlorine atom becomes a chloride ion
• Cl• 2-8-8 (18 electrons but only 17 protons)
– Same electron configuration as a noble gas (Ar)
but has fewer protons. Electrons repel each
other and the radius increases.
 2- ions are even larger than – ions
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Regents Question: 06/03 #60
As a neutral sulfur atom gains two electrons, what
happens to the radius of the atom?
It gets bigger
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Regents Question: 06/03 #61
After a neutral sulfur atom gains two electrons, what
is the resulting charge of the ion?
2-
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Regents Question: 08/02 #23
Which electron configuration is correct for a
sodium ion?
(1) 2–7
(2) 2–8
(3) 2–8–1
(4) 2–8–2
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Regents Question: 08/02 #47
Which ion has the same electron configuration as
an atom of He?
(1) H–
- means gains 1 electron
(2) O2–
2- means gains 2 electrons
(3) Na+
+ means loses 1 electron
(4) Ca2+
2+ means loses 2 electrons
GIN LIP
Gaining electrons makes Ions Negative
J Deutsch 2003
Losing electrons makes Ions Positive
39
Regents Question: 06/02 #39
Which of the following ions has the smallest radius?
(1) F(2) Cl(3) K+
(4) Ca2+
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Regents Question: 06/02 #30
As an atom becomes an ion, its mass number
(1) Decreases
(2) Increases
(3) Remains the sam
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Regents Question: 06/02 #10
Compared to the radius of a chlorine atom, the radius of
a chloride ion is
(1) Larger because chlorine loses an electron
(2) Larger because chlorine gains an electron
(3) Smaller because chlorine loses an electron
(4) Smaller because chlorine gains an electron
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Trends in Electronegativity
 Electronegativity – the relative ability of an atom
to attract electrons (in a chemical bond)
 Fluorine (F) has the highest electronegativity and
is assigned the value 4.0
 Francium (Fr) has the lowest electronegativity.
 Going down a group, electronegativity decreases
because there are more shells and the electron
being attracted is far from the protons
 Going across a period, electronegativity increases
because there are more protons in the nucleus to
attract the electrons. (same number of shells)
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Regents Question: 06/02 #11
Which of the following atoms has the greatest tendency
to attract electrons?
(1) Barium
(2) Beryllium
(3) Boron
(4) Bromine
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Regents Question: 01/03 #10
The strength of an atom’s attraction for the electrons in a
chemical bond is the atom’s
(1) Electronegativity
(2) Ionization energy
(3) Heat of reaction
(4) Heat of formation
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Trends in First Ionization Energy
 First ionization energy is the amount of energy
needed to remove the most loosely held electron
from an atom in the gaseous state.
 Going down a group, first ionization energy
decreases because there are more shells and the
electron being attracted is far from the protons
 Going across a period, first ionization energy
increases because there are more protons in the
nucleus to attract the electrons. (same number of
shells)
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Regents Question: 01/03 #7
From which of these atoms in the ground state can a
valence electron be removed using the least amount
of energy?
(1) Nitrogen
(2) Carbon
(3) Oxygen
(4) Chlorine
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Trends in Metallic Properties
 Metals want to lose electrons to complete their
outer shells
 Metals form positive (+) ions
 Metals have low electronegativity
 Metals have low first ionization energy
 Metallic properties (characteristics) decrease as
you go to the right across a period
 Metallic properties increase as you go down a
group
 Going towards Francium (Fr), metallic properties
increases.
Anything that increases an atom’s ability to lose electrons,
increase the atoms metallic characteristics.
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Trends in Nonmetallic Properties
 Nonmetals want to gain electrons to complete
their outer shells
 Nonmetals form negative (-) ions
 Nonmetals have high electronegativity
 Nonmetals have high first ionization energy
 Nonmetallic properties (characteristics) increase
as you go to the right across a period
 Nonmetallic properties decrease as you go down a
group
 Going towards Fluorine (F), nonmetallic
properties increases.
Anything that increases an atom’s ability to gain electrons,
increase the atoms nonmetallic characteristics.
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Regents Question: 06/02 #32
Which of the following Group 15 elements has the
greatest metallic character?
(1) Nitrogen
(2) Phosphorous
(3) Antimony
(4) Bismuth
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Regents Question: 06/02 #5
Which are two properties of most nonmetals?
(1) High ionization energy and poor electrical
conductivity
(2) High ionization energy and good electrical
conductivity
(3) Low ionization energy and poor electrical conductivity
(4) Low ionization energy and good electrical
conductivity
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Regents Question: 06/02 #67-69
Element
Atomic Number
Electronegativity
Beryllium
4
1.6
Boron
5
2
Carbon
6
2.6
Fluorine
9
4.0
Lithium
3
1.0
Oxygen
8
3.4
On the grid in your answer booklet, set up a scale for electronegativity
on the y-axis. Plot the data by drawing the best-fit line.
Using the graph, predict the electronegativity of nitrogen
For these elements, state the trend in electronegativity in terms of atomic
number.
J Deutsch 2003
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Regents Question: cont’d
J Deutsch 2003
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Regents Question: cont’d
4
3
2
1
J Deutsch 2003
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Regents Question: Cont’d
4
3
2
1
On the grid in your answer booklet, set up a scale for electronegativity
on the y-axis. Plot the data by drawing the best-fit line.
Using the graph, predict the electronegativity of nitrogen
3.0
For these elements, state the trend in electronegativity in terms of atomic
number. As the atomic number increases, the
electronegativity increases.
J Deutsch 2003
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