Download THE PERIODIC TABLE

HOLT CHEMISTRY
CHAPTER 4
THE PERIODIC TABLE
I. How Are Elements Organized?
Objectives:
• Describe the historical development of the periodic table.
• Describe the organization of the modern periodic table according to the periodic law.
A. Patterns in Element Properties
1. The elements vary widely in their properties, but in an orderly way.
2. English chemist, John Newlands was the first to arrange the known elements
according to their atomic masses and properties.
a. He noticed that the properties of the elements repeated every eighth element.
b. He called this pattern the law of octaves.
3. Russian chemist, Dmitri Mendeleev used Newlands observation to produce the first
periodic table of the known 63 elements.
a. His table was also based on atomic mass.
b. He left gaps for elements that did not fit and predicted their future discovery.
4. English chemist, Henry Mosley was the first to arrange the elements according to
their atomic number.
a. He used the x-ray spectra of 38 elements to find the correlation between the
atomic mass of the elements and their properties.
b. Upon rearranging Mendeleev’s periodic table, the discrepancies were gone.
B. The Periodic Law
1. The periodic law states that the repeating physical and chemical properties of
elements change periodically with their atomic number.
2. Valence electrons are those electrons in an atom that are found in the outermost
energy level and determine that element’s chemical properties.
3. Vertical columns called groups on the periodic table have the same number of
valence electrons.
4. Horizontal rows on the periodic table are called periods and contain elements with the
same number of energy levels.
II. Tour of the Periodic Table
Objectives:
• Locate the different families of main-group elements on the periodic table, describe their
characteristic properties, and relate their properties to their electron configurations.
• Locate metals on the periodic table, describe their characteristic properties, and relate
their properties to their electron configurations.
A. The Main-Group Elements
1. Elements in groups 1, 2 and 13-18 and the s-and p- periods are known as the maingroup elements.
2. Because of their wide range of properties, they are also known as the representative
elements.
3. The main-group elements silicon and oxygen account for four of every five atoms
found on or near Earth’s surface.
4. Four groups within the main-group elements have special names.
a. The Alkali Metals:
(i) make up group 1.
(ii) are so named because they react with water to form alkaline solutions.
(iii) are very reactive.
(iv) all have one valence electron that they ALWAYS give up when they react.
b. The Alkali Earth Metals
(i) make up group 2.
(ii) are only slightly less reactive than the Alkali Metals.
(iii) have two valence electrons that they ALWAYS give up when they react.
c. The Halogens:
(i) make up group 17.
(ii) are the most reactive non-metals.
(iii)have 7 valence electrons.
d. The Nobel Gases
(i) make up group 18.
(ii) have very low reactivity because of their full complement of valence
electrons.
(iii)used to be called inert gases because they were thought to be completely nonreactive.
5. Hydrogen Is in a Class by Itself.
a. is the most common element in the universe making up 3 out of every 4 atoms
therein.
b. has only one proton and one electron.
c. reacts with a wide variety of other elements.
d. reacts with oxygen explosively to form water H2O which is the foundation of life
on Earth.
B. Most Elements Are Metals
1. Metals share many properties.
a. Excellent conductors of both electricity and heat.
(i) The worst conducting metal will conduct electricity 100,000 times better than
the best non-metallic conductor.
b. Ductile – meaning they can be draw into a wire.
c. Malleable – meaning they can be beaten into a sheet.
(i) Gold is the most malleable of all metals.
d. Shiny – most metals are shiny because of their electron arrangements.
2. Transition metals occupy the middle of the periodic table.
a. They constitute groups 3-12.
b. They are sometimes called d-block elements because of their position on the
periodic table.
c. Do not have identical outer electron configurations in the groups (ex. group 10)
d. May lose different numbers of valence electrons.
3. The Lanthanides and Actinides Fill f-orbitals.
a. They are also pulled out and placed at the bottom of the periodic table to keep the
periodic table from becoming awkwardly wide.
b. Elements found within the lanthanides are about as reactive as the alkaline earth
metals and some are used to make the screens for television picture tubes.
c. Because of their large unstable nucleus’, the actinides are all radioactive the best
known of which is uranium.
4. Other properties of metals can be interesting.
a. Tungsten has the highest melting point of any element at 43220C.
b. Mercury melts at -390C making it a liquid at room temperature.
c. Metals can mix with one or more other elements resulting in an alloy with unique
properties.
(i) Brass – a mixture of copper and zinc.
(ii) White Gold - a mixture of gold and platinum.
(iii)Yellow Gold – a mixture of gold and copper.
(iv) Steel – a mixture of iron and 0.2% - 1.5% carbon.
(v) Stainless Steel – a mixture of iron, carbon, and chromium.
(vi) Sterling silver – a mixture of silver and copper.
III. Trends in the Periodic Table
Objectives:
• Describe periodic tends in ionization energy, and relate them to the atomic structures of
the elements.
• Describe periodic trends in atomic radius, and relate them to the atomic structures of the
elements.
• Describe periodic tends in ionic size, electron affinity, and melting and boiling points,
and relate them to the atomic structures of the elements.
A. Periodic Trends
1. A trend is a particular change in a certain direction.
2. The periodic table reveals trends in the properties of the elements.
3. EX. – the reactivity of group 1 elements increases as we go down the group.
4. Trends can be explained in terms of electron configuration.
5. The primary contributors to periodic trends are electron shielding and effective
nuclear charge.
B. Ionization Energy
1. Ionization energy is the energy required to remove an electron from an atom thus
making it an ion.
2. Because of electron shielding, ionization energy decreases as we move down a group
and increases as we move from left to right across a group.
C. Atomic Radius
1. Atomic radius increases as we move down a group and decreases as we move from
left to right across the periodic table because of electron affinity.
2. Atomic radii levels off as we reach the end of a period for the same results.
D. Electronegativity
1. Electronegativity (an atom’s attraction for electrons) decreases as you move down a
group and increases as you move from left to right across a period.
E. Other Periodic Trends
1. Ionic size increases as we move down a group and decreases as we move from left to
right across the periods.
2. Electron affinity (an atom’s energy change when it gains an electron) decreases as we
move down a group and increases as we move from left to right across a period.
IV. Where Did the Elements Come From?
Objectives:
• Describe how the naturally occurring elements form.
• Explain how a transmutation changes one element into another.
• Describe how particle accelerators are used to create synthetic elements.
A. Natural Elements
1. Of all the elements listed in the periodic table, 93 are found in nature.
2. Of these, three are found only in the spectra of stars.
B. Transmutations
1. The first recorded attempts to produce transmutations were when the alchemists of
the middle ages tried to change some metals into gold.
2. Transmutations are nuclear reactions that occur when subatomic particles traveling at
extremely high speeds strike other nuclei and fuse together.
V. Synthetic Elements
1. By using particle accelerators, scientists have been able to create elements not found
in nature.
2. Any element with more than 92 protons in its nucleus is a synthetic element.
3. Scientists are only able to produce a few atoms of synthetic elements at a time and
they only last for fractions of a second before decaying into a more stable form.