Periodic Table

CPS Chemistry

What You Need To Know

• Periodicity– Central Concepts:

• Repeating (periodic) patterns of physical and chemical properties occur among elements that define families with similar properties.

• The periodic table displays the repeating patterns, which are related to the atoms’ outermost electrons.

The Details

• Explain the relationship of an element’s position on the periodic table to its atomic number.

• Identify families (groups) and periods on the periodic table.

• Use the periodic table to identify the three classes of elements: metals, nonmetals, and metalloids.

• Relate the position of an element on the periodic table to its electron configuration and compare its reactivity to the reactivity of other elements in the table.

• Identify trends on the periodic table– ionization energy– electronegativity– relative sizes of atoms and ions

History of the Periodic Table

– 1864 John Newlands• An English scientist , he put forward his law of

octaves • He arranged all the elements known at the time

into a table in order of relative atomic mass• When he did this, he found that each element was

similar to the element eight places further on• For example, starting at Li, Be is the second

element, B is the third and Na is the eighth element.

Newland’s Table• Newlands' table showed a repeating or

periodic pattern of properties, but it had problems.

• For example, he put iron in the same group as oxygen and sulphur, which are two non-metals. As a result, his table was not accepted by other scientists

Mendeleev's Periodic table• 1869 Dmitri Mendeleev 1834 -1907

• Mendeleev also arranged the elements known at the time in order of relative atomic mass, but he did some other things that made his table much more successful.

• He realized that the physical and chemical properties of elements were related to their atomic mass in a 'periodic' way, and arranged them so that groups of elements with similar properties fell into vertical columns in his table.

Part of Mendeleev's periodic table

Gaps and predictions

• Sometimes this method of arranging elements meant there were gaps in his horizontal rows or 'periods'.

• But instead of seeing this as a problem, Mendeleev thought it simply meant that the elements which belonged in the gaps had not yet been discovered.

• He was also able to work out the atomic mass of the missing elements, and so predict their properties. And when they were discovered, Mendeleev turned out to be right.

• For example, he predicted the properties of an undiscovered element that should fit below aluminum in his table

Modern Periodic Table

• Using atomic number instead of atomic mass as the organizing principle was first proposed by the British chemist Henry Moseley in 1913, and it solved anomalies like this one.

Atomic Number Arrangement

Modern Periodic Law

• Properties of the elements are a periodic function of their atomic number.

• In other words, when the elements are arranged in order of increasing atomic number, elements with similar properties appear at regular intervals.

How to interpret the PTE

• Groups or columns – Read from top to bottom

• Periods or rows– Read across

– The relationships vary depending on what you are looking for

Periods

• Same energy level

• Remember those pesky quantum numbers? • Here is where they begin to make sense! ;)

• There are seven periods

• Each of which begins with an atom having only one valence electron

• Ends with a complete outer shell structure of an inert gas.

Metals,

• Are found on the left side of the table with the most active metal in the lower left corner

• Since the most active metals react with water to form bases, the Group I metals are called alkali metals

• Metals in the first two groups are the light metals

• Those toward the center are called heavy metals

Alkali Metals

• Are the elements in Group IA of the periodic table.

• All six elements have the properties of metals except are softer and less dense

• Can be cut with a knife• Are so reactive that they are never found as

elements in nature but are always combined with other elements

• Have only one electron in their outermost shell• Form positive ions.

Alkaline Earth Metals

• Are harder and more dense than the alkali metals

• Have higher melting points and boiling points• Are highly reactive, but not as active as the alkali

metals• Are never found free in nature• Have two electrons in their outermost energy

level• Form positive ions.

Transition Metals

• Have properties similar to one another and to other metals

• But do not fit in with those of any other family

• Most transition metals are excellent conductors of heat and electricity

• Most have high melting points and are hard

• Transition metals are much less active than the alkali and alkaline earth metals

• Many transition metals combine chemically with oxygen to form compounds called oxides

• Many transition metals have more than one oxidation number

• Transition metals form compounds that are brightly colored.

Nonmetals

• Nonmetals are found on the right side

• With the most active nonmetal in the upper right hand corner of the chart

Metalloids

• Elements found along the dark line in the periodic table are called metalloids

• They are the elements which have certain characteristics of metals and other characteristics of nonmetals.

• Some examples of metalloids are boron, silicon, arsenic, and tellurium

Noble Gasses

• Noble or inert gasses are on the far right

• .