Periodic Properties

​Periodic Table

Groups, Periods & Properties

​Early History

Early Attempts to Organize Elements

• By the year 1700, only a handful of elements had been identified and isolated. Several of these, such as copper and lead, had been known since ancient times.

• As scientific methods improved, the rate of discovery increased.

• ​There were limitations to Dobereiner's triads. English chemist John Newlands (1838-1898) ordered elements in increasing order of atomic mass. He noticed that every eighth element exhibited similar properties. He called this the "Law of Octaves".

1864

• ​A German chemist named Johann Dobereiner (1780-1849, placed groups of three elements into groups called triads. These triads were based on physical and chemical properties

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1829

​Early History

​Early History

Limitations

• Much like Dobereiner, there were issues with Newlands' "Law of Octaves". There were elements missing from his table, and the law did not seem to hold true for elements that were heavier than calcium.

• Newlands' work was largely ignored and even ridiculed by the scientific community in his day. It wasn't until years later that another, more extensive periodic table effort would gain greater acceptance and Newlands' work would be appreciated. ​

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​Dmitri Mendeleev (1836-1907)

• In 1869, Russian chemist and professor Dmitri Mendeleev published a periodic table of elements. ​He organized his table by increasing atomic mass and noticed certain similarities in chemical behavior repeated at regular intervals. This type of repeating pattern is called "periodic".

• These repetitions led Mendeleev to leave spaces in his table where he predicted elements would fit that had yet to be discovered. ​

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Mendeleev was able to predict the properties of several elements that had yet to be discovered remarkably well.

This is one example. ​

​Mendeleev's Predicted Elements

​Henry Moseley (1887-1915)

• ​When Mendeleev created his periodic table, nobody knew about the existence of the nucleus. (Remember: Rutherford conducted his gold foil experiment in 1911.

• In 1913, English physicist Henry Moseley examined x-ray spectra of a number of chemical elements by firing x-rays through crystals of the element and studying the wavelengths of the radiation. He found that there was a relationship between wavelength and atomic number.

​Henry Moseley (1887-1915)

• ​Moseley realized that elements of the periodic table should be arranged in order of increasing atomic number, rather than increasing atomic mass.

• ​When ordered by increasing atomic number, any discrepancies within Mendeleev's table disappeared. Both Moseley and Mendeleev are credited with creating the modern periodic law: When elements are arranged by increasing atomic #, there is a periodic repetition of their chemical and physical properties.

• Our modern periodic table is still changing, with new elements being discovered, while others have been artifically synthesized.

• There are 18 groups (columns) & 7 periods (rows).​

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Modern Periodic Table

Multiple Choice

In 1869, ______________ developed a periodic table that was organized by increasing atomic mass and grouped by their periodic properties.

• Dmitri Mendeleev

• Henry Moseley

• Johann Dobereiner

• John Newlands

Multiple Choice

In 1913, Henry Moseley realized that the periodic table should be arranged in order of increasing _____________.

• atomic mass

• atomic number

• law of octaves

• triad energy

Multiple Choice

When elements are arranged by increasing atomic number, there is a periodic repetition of their chemical and physical properties. This is called the _________ law.

• atomic

• quantum

• nuclear

• periodic

Multiple Choice

The modern periodic table has _______ groups and _______ periods.

• 8, 7

• 18, 7

• 7, 18

• 10, 18

​Metals, Nonmetals, & Metalloids

Metals

• Most of the elements on the periodic table are metals.​ They are found on the left side of the stair-step line (except Hydrogen).

• Metals are elements that:

  • conduct electricity. ​

  • have relatively high melting points (explains why most are solids at room temperature "except Mercury")

Metals are good conductor of heat and electricity. This is why metals such as iron, copper, and aluminum are used for pots and pans.

Good Conductors

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Metals are generally shiny. This is because they reflect much of the light that strikes them.

Luster

Ductility is the ability to be drawn into thin, long shapes. Malleability is the ability to be hammered into thin sheets without breaking.

Ductile/Malleable

Electricity is the flow of electrons. Metals tend to give up electrons because they have 1 or 2 valence electrons, explaining why they are good conductors.

Electrical Conductors

​Metals

​Nonmetals

• Nonmetals are elements that generally DO NOT conduct electricity. They are located on the right side of the stair-step line.

• Nonmetals have properties such as:

  • relatively low boiling point (mostly gases at room temperature)

  • Dull and brittle as solids

  • Highly reactive nonmetals tend to gain electrons

Metalloids

• Smallest category of elements (6)

• Found along the stair-step line. Sometimes called "Semiconductors".

• Silicon (Si), Boron (B), Germanium (Ge), Arsenic (As), Antimony (Sb), and Tellurium (Te). ​

• Have properties of both metals and nonmetals.​

• Chemical behaviors depends mainly on valence electrons. ​

s block - Groups 1 & 2 (including Helium)

p block - Groups 13-18

d block - Groups 3-12​

f block - Lanthanides & Actinides​

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​Blocks of the Periodic Table

Multiple Choice

Which type of elements make up the majority on the periodic table?

• metals

• nonmetals

• metalloids

Multiple Choice

Where are the nonmetals found on the periodic table?

• left side of the stair-step line

• right side of the stair-step line

• along the stair-step line

Multiple Choice

Which type of substance has the following properties:

1. relatively high melting and boiling point

2. generally solids at room temperature

3. ductile and malleable

4. generally good conductors of heat and electricity

• metals

• nonmetals

• metalloids

Multiple Choice

Consider Fluorine's (F) location on the periodic table. Is it a metal, nonmetal, or metalloid?

• metal

• nonmetal

• metalloid

Multiple Choice

Consider Magnesium's (Mg) location on the periodic table. Is it a metal, nonmetal, or metalloid?

• metal

• nonmetal

• metalloid

Multiple Choice

True or False: Metals tend to gain electrons, making them poor conductors of electricity.

• True

• False