Transcript Atoms and the Periodic Table

Chapter 4
Section 3
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The Periodic table groups similar elements
together to make it easier to predict the
properties of an element based on its
location.
How is the Periodic Table organized?
◦ Based on the number of protons, or atomic number,
an element has in the nucleus of an atom.
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Periodic Law
◦ States that the repeating chemical and physical
properties of elements change periodically with the
atomic numbers of the elements.
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Periods
◦ Horizontal rows of elements in the Periodic Table.
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Groups
◦ Vertical columns of elements in the Periodic Table.
How Are Elements Classified?
Figure 22 B, Page 120
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Metals
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Nonmetals
◦ An element that is lustrous, ductile, malleable and
conducts heat and electricity well. Lose electrons to
form cations.
◦ An element that conducts heat and electricity poorly.
 Can be solids, liquids or gases. Solids are typically dull and
brittle. Gain electrons to form anions.
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Metalloids
◦ An element or compound that conducts electric current
better than an insulator but not as well as a conduct
does.
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Alkali metals
◦ The elements in Group 1 on the Periodic Table.
◦ Soft and shiny
◦ React violently with water.
http://www.youtube.com/watch?v=uixxJtJPVXk
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Why do these metals react so violently?
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Alkaline-earth
◦ Group 2 elements on the Periodic Table.
◦ Still react with water, but not violently.
◦ Calcium compounds
 Used for construction
 “skeletons” of animals
 Strength for teeth and bones.
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Transition Metals
◦ Elements from groups 3-12 of the Periodic Table.
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Actinides and Lanthanides
◦ Located below the Periodic Table
◦ Lanthanides are also considered Rare Earth Metals,
along with scandium and yttrium.
 Essential to medical diagnosis equipment and almost
all military systems. Critical components for modern
electronic technologies.
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All metals conduct heat and electricity.
They are all ductile, malleable and lustrous.
Most metals can be stretched and shaped into
flat sheets or pulled into wires.
Radioactive
◦ The nuclei of the atoms are continually decaying to
produce different elements.
◦ Elements with atomic number greater than 92 are
man-made, and from 84 and greater are
radioactive.
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Carbon
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Graphite, pencil lead
Diamonds
Sugar, or glucose
Chlorophyll
Fullerenes
Oxygen and Nitrogen are the most plentiful
gases in the air we breathe.
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Halogens
◦ Group 17 on the Periodic Table.
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Chlorine protects you from harmful bacteria.
◦ In gas form, it is a poisonous yellowish green gas
that consists of two chlorine atoms bonded
together, Cl2.
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Fluorine is a poisonous yellowish gas.
Bromine is a dark red liquid.
Iodine is a dark purple solid.
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Diatomic Gases
◦ Made up of two atoms
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There are 7 diatomic atoms:
◦ Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine,
Bromine, and Iodine.
◦ H2, N2, O2, F2, Cl2, Br2, and I2
How Are Elements Classified?
Figure 22 B, Page 120
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Noble Gases
◦ Group 18 on the Periodic Table.
◦ The gases are inert.
◦ Found as single atoms in nature, not molecules.
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Metalloids
◦ An element or compound
that conducts electric
current better than an
insulator but not as well as
a conductor.
 Nonmetals that have some
properties of metals.
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Found along the stairstep line.
7 metalloids:
◦ Boron, Silicon, Germanium,
Arsenic, Antimony,
Tellurium, and Polonium.
◦ B, Si, Ge, As, Sb, Te, Po
Figure 31, Page 127
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Boron
◦ Extremely hard, added to steel to increase hardness and
strength at high temperatures.
◦ Often used for heat-resistant glass.
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Arsenic
◦ Shiny solid that tarnishes when exposed to air.
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Antimony
◦ Bluish white brittle solid that shines like a metal.
◦ Found in fire retardants.
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Tellurium
◦ Is a silvery white solid whose ability to conduct increases
slightly with exposure to light.
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Silicon
◦ Accounts for 28% of the mass of the Earth’s crust.
◦ Sand, silicon dioxide: SiO2.
◦ Computer chips, transistors, LED display screens,
and solar cells.
◦ Impurities increase ability to conduct electricity.
Section 2
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Ionization
◦ An atom gains or loses valence electrons in order to
have a full outermost ‘s’ and/or ‘p’ orbital.
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When atoms gain or lose electrons, the atom
is no longer neutral.
Ion
◦ An atom or group of atoms that has lost or gained
one or more electrons, has a negative or positive
charge.
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Cation
◦ Positively charged ion that has lost an electron.
 All metals are cations.
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Anion
◦ Negatively charged ion that has gained an electron.
 All nonmetals are anions.
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Atomic number, Z
◦ The number of protons in the nucleus of an atom.
◦ The atomic number never changes for a given
element.
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Mass number, A
◦ the sum of the numbers of protons and neutrons in
the nucleus of an atom.
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Isotope
◦ An atom that has the same number of protons as
other atoms of the same element do but has a
different number of neutrons.
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Hyphen notation
◦ The name of the element, hyphen, and then the
mass number of the isotope.
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Isotopes of Hydrogen
◦ Protium-1
◦ Deuterium-2
◦ Tritium-3
Isotope
Atomic
Number
Mass
Number
Protons
Electrons
Neutrons
Protium
1
1
1
1
0
Deuterium
1
2
1
1
1
Tritium
1
3
1
1
2
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Finding the number of Neutrons:
◦ Mass Number – Atomic Number = Number of
Neutrons
◦ Example: Oxygen-18
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Average Atomic Mass
◦ The weighted average of the masses of all naturally
occurring isotopes of an element.
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Using average atomic mass, round to nearest
whole number to find the mass number.
Atomic Mass unit (amu)
◦ A unit of mass that describes the mass of an atom.
Section 1
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What are atoms?
◦ Tiny particles that determine the properties of all
matter.
◦ Translates to “unable to be divided”.
◦ The smallest part of an element that maintains that
element’s properties.
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Who was Democritus?
◦ A Greek philosopher who believed the movements
of atoms caused the changes in matter that he saw.
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John Dalton
◦ An English school teacher who developed his own
atomic theory that formed the foundation for the
modern atomic theory.
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Dalton’s Atomic Theory:
◦ Atoms of different elements can join to form
compounds.
◦ All atoms of a given element are exactly alike.
◦ Atoms cannot be divided.
 Are the last two assumptions true?
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Atoms can actually be
divided into smaller
particles. What are the
particles?
◦ Proton- subatomic particle
that has a positive charge,
found in the nucleus.
◦ Neutron- subatomic
particle that has no charge,
found in the nucleus.
◦ Electron- subatomic
particle that has a negative
charge, found outside the
nucleus in the electron
cloud.
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Electrons are about 2000
times smaller than a
proton and a neutron.
Table 1, Page 106
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Nucleus- center of an atom where the
protons and neutrons reside.
Electron cloud- the area where the electrons
orbit around the nucleus of an atom.
Do atoms have a charge?
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Models have been adapted as new
information has been discovered.
Niels Bohr suggested that:
◦ Electrons move in set paths around the nucleus.
◦ Each electron has a certain energy, and the path
defines the electrons energy level.
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How can electrons
move from one energy
level to another?
Absorption◦ the take in of energy.
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Emission◦ the release of energy.
Figure 5, Page 107
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Bohr’s model no longer explains electrons
behavior, but helps in understanding energy
levels.
Do not orbit in definite paths.
In the current model of the atom, electrons
move like waves.
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Heisenberg Uncertainty Principle
◦ Cannot predict where an electron is located and the
speed at the same time.
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We can calculate the chance of finding an
electron at a certain location.
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Each energy level can
have a certain number
of electrons.
Can determine energy
level by a simple
equation: 2n2.
In each energy level,
there are certain
“orbitals” that the
electrons can be found
in.
Figure 7, Page 108
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Valence electrons◦ Electron(s) that are found in the outermost shell of
an atom.
◦ Valence electrons determine the atom’s chemical
properties and its ability to form bonds.
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How many valence electrons can an atom
have?
How can we determine valence electrons in an
atom?
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Orbitals◦ The regions in an atom where electrons are going
to be found 90% of the time.
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There are four different orbitals.
◦ S, p, d, and f
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Each orbital can be occupied by a total of two
electrons.
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The ‘s’ orbital
The lowest energy
occupied orbital.
There is only one
orbital for ‘s’.
Spherically shaped.
Figure 8, Page 109
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The ‘p’ orbital
There are three
orbitals for ‘p’.
The ‘p’ orbital can
have a total of 6
electrons.
This orbital has a
dumbbell shape.
Figure 9, Page 109
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The ‘d’ and ‘f’ orbitals are more complex than
‘s’ and ‘p’.
The ‘d’ orbital has 5 orbitals and can hold a
total of10 electrons.
The ‘f’ orbital has 7 orbitals and can hold a
total of 14 electrons.
Location of the orbitals
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Electron configurations◦ The arrangement of electrons in the orbitals.
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‘d’ orbitals have a lower coefficient than ‘s’
and ‘p’ when written.
How do we write them?
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Noble Gas Configuration
◦ The short hand way of writing electron
configurations.
◦ Take the noble gas that comes before the element
that the configuration is being written for.
◦ Put the noble gas in brackets [ ].
◦ Write the rest of the configuration like normal.