Leanne Jamison

First Edition

The Periodic TableHistory and Trends

1 Chapter 1

The Periodic Table: A Brief History

Dmitri Mendeleev

2

Before Its InventionWhile Gold and Silver have been around and known sense mod-ern society, the first official element found was discovered in 1649 by a man named Hennig Brand. He discovered phospho-rous. This began a torrent of discoveries in regards to elements over the next several hundred years. However, the Father of the Periodic Table did not come until 1834.

“The Father of the Periodic Table”Dmitri Mendeleev (1834-1907) was born in Siberia to a teacher of Russian literature and philosophy. While not originally an outstanding student, he found a love for Chemistry and began in his adulthood to put together the elements in order of increasing atomic mass. He moved elements from where they previously would have been assigned, however, because they did not properly fit the surrounding elements properties. This placed some elements out of order by atomic weight, and Men-deleev cunningly decided that the gaps present indi-cated the presence of unknown elements. These were later found and fit into the gaps perfectly. Mendeleev pre-dicted the presence of 10 new elements, and seven

Section 1

A Brief History

3

were later found to exist. Mendeleev was ahead of the knowledge of the noble gases. Moreover, his table organ-ized the nature of elements in a way in which they corre-lated with one another, and this was before scientists could discern why some elements occur similarly to oth-ers.

Here is a fun song that shows just how involved the peri-odic table really is, and gives you an idea of just how far the periodic table has come since Dimitri Mendeleev pub-lished his first table: http://www.youtube.com/watch?&v=K8eT-k4f7_8

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do tempor incididunt ut labore et dolore magna aliqua.

MOVIE 1.1 Lorem Ipsum dolor amet, consectetur

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After Mendeleev

! Mendeleev was not the first to publish a peri-odic table, his was just the most innovative and last-ing; we still use the base of it today. Lothar Meyer, a German chemist, also created a periodic table of sorts in a book he published around the same time Mendeleev published his. Yet, his table was much more abbreviated.

! It was not until Neil Bohr that the question of why the peri-odic table exists was finally answered. He was the first scientist to begin studying the existence of electrons in quantized shells. The last alteration to the periodic table was done in 1940 with the discovery of plutonium. Glenn Seaborg won the Nobel Prize in 1951 for his discovering multiple elements and helping to form the periodic table we study today.

Now that you know a brief history of the periodic table, here is a short quiz to help you test your knowledge: http://www.ck12.org/chemistry/Early-History-of-the-Periodic-Table/quiz/Early-History-of-the-Periodic-Table-Quiz/

Then, answer the quiz questions written in this book. The an-swers are on the following page.

Section 2

A Brief History: After Mendeleev

5

1. During what century was the first periodic modern periodic table published? ! a. It’s always been around

! b. During the 15th century

! c. During the late 1800s

2. Who was the first to assemble the elements by their properties, how did this change the peri-odic table?! a. Dmitri Mendeleev. This al-lowed for gaps in the table that would later be filled by elements not yet discovered.

! b. Albert Einstein. This was the first table to include the Halo-gens.

! c. It is unknown who first as-sembled the elements by their properties.

3. True of False: Dimitri Mendeleev created a period table of ele-ments that had all of the elements present- even ones that had not yet been discov-ered.

a. True

b. False

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1. Answer C 2. Answer A 3. Answer B, false. Dimitri Mendeleev did leave spaces in the peri-odic table for elements that had not yet been dis-covered based on gaps in known element’s atomic numbers. He did not however have all of those elements present, he left gaps for them.

2 Chapter 2

Periodic Trends

Why Are They Important?

8

Section 1

Periodic Trends This section will discuss the nonmetals, metals, anions, cations, and the groups that hold specific relevance, such as the Noble Gases.

9

! I will not go into a discussion on quantum mechanics or the different orbitals as this would require a much larger discus-sion than covered in the scope of this book. That being said, on the periodic table, Groups 1-12 are generally considered met-als. Groups 13-18 are generally non-metals. Metals are much more likely to lose electrons, and subsequently become cati-ons. Conversely, non-metals are more inclined to gain elec-trons, and subsequently become anions.

! Now, just to review, in an atom there are three subatomic particles that we will discuss: protons, neutrons, and electrons. On the periodic table, the number above the element is that ele-ment’s atomic number. As you can see, this number increases from left to right across the columns. That is because, as de-scribed in chapter 1, atoms are organized by their atomic num-ber. So, what is an atomic number? Well, and atomic number is the number of protons present in an atom. A proton is a posi-tively charged particle that exists in the nucleus of an atom along with the neutrons. Neutrons are neutral subatomic parti-cles. Electrons are negatively charged particles that exist out-side of the nucleus, and they move in and out of different elec-tron orbitals and shells that are quantized distances apart from one another.

! So, what do protons, neutrons, and electrons have to do with cations and anions. Moreover, what are cations and ani-

ons? What is an ion? How about you watch this awesome You-Tube video to find out.

https://www.youtube.com/watch?v=WWc3k2723IM

! Now that you know about cations and anions, and have an idea of where metals and nonmetals are on the periodic table, it is important to understand why there are some special rows pre-sent.

MOVIE 2.1 Video describing what Ions, Cations, and Anions are

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Recall that in atoms, there are valence electrons. Valence elec-trons are the electrons that exist in an atom's outermost shell. Picture an onion. At the very center of that onion is the nucleus. Remember, this nucleus is where the neutrons and protons ex-ist. Now, start to add the many layers that are present in an on-ion. When you get to that very outermost layer, the outside of the onion, this is where the valence electrons would exist in an atom. Generally speaking, atoms are the most unreactive when 8 electrons exist in this outermost shell. They are happiest with this configuration, and the reactivity and trends that exist with

Group Number Group Name

1 Alkali Metals

2Alkaline Earth

Metals

17 Halogens

18 Noble Gases

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the periodic table help show very visibly why elements react they way they do- they are attempting to achieve that 8 electron configuration. All electrons are working towards getting as close as possible to the last row, row 18, due to the fact that this row has elements with that full octet.

On the periodic table, there are a couple imperative groups that exist with similar chemical properties. These properties are ex-tremely useful to science. This youtube video clearly shows what these groups are, and why they act the way they do.

http://www.oercommons.org/courses/chemistry-groups-of-the-periodic-table/view

MOVIE 2.2 Video Describing Periodic Groups

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How the Trend Works So far, the organization of the periodic table has been explained by atomic number. Yet, it goes much deeper than that. There are multiple trends that exist that indicate what size atoms are, how reactive they are, and what atoms look like based on where they are on the periodic table. On the periodic table, as more electrons are added to the outermost shell of the element, the larger the atom is going to be. This explains why the trend of atomic radii size increases as you move down a row.

Atomic Radii- half the distance between the nuclei of identical atoms that are bonded together, (Periodic Trends, cK-12)

When you move down a row you are adding another shell full of negatively charged electrons which are repulsed by the posi-tively charged nucleus. Atoms are also larger as you move to the left. This is due to the fact that across a column a proton is added to the nucleus as you move right. This creates more at-traction between the electron cloud and the nucleus and subse-

quently draws the electrons in more tightly- making a smaller atom. This creates the visual trend that follows:

If you would like more information on the Atomic Radii trend, check out this awesome website:

http://www.ck12.org/section/Periodic-Trends-%253A%253Aof%253A%253A-The-Periodic-Table-%253A%253Aof%253A%253A-CK-12-Chemistry-Intermediate/

Section 2

Atomic Radii Size

How The Trend Works

! In a covalent bond, two atoms come together and form a bond by sharing their valence electrons. However, this is not always an equal sharing and some atoms have a much better capability of finding and attracting the valence electrons of other elements. Once again, this ability to attract electrons is a trend that is visible on the periodic table. This is the trend of electronegativity.

Electronegativity- an atom’s measurable ability to attract electrons within a bond in a compound (Periodic Trends, cK-12)

This trend relates to an atoms number of valence electrons. Recall that all atoms want eight valence

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electrons, like the noble gases. As elements get closer to this number, they are going to be more inclined to react and gain or lose electrons in order to react eight. This correlates to the trend in electronegativity. However, electronegativity is the abil-ity to attract electrons, so atoms that gain electrons are more electronegative. On the periodic table, the Halogens have seven valence electrons. Moreover, Fluorine is the smallest of these atoms according to the trend of atomic radii. Subse-quently, Fluorine is the most electronegative element on the pe-riodic table, and the trend fans out from this:

Section 3

Electronegativity

How The Trend Works

On the periodic table, it has already been discussed that there are valence electrons and that these electrons reside within specific orbitals. Yet, there is yet another trend that allows you to visually see which orbital an elements valence electrons are residing within. Recall that on the periodic table, the first two rows are the metals, followed by ten rows of transition metals, and this is followed by six rows of non-metals. With regard to orbitals, there is just one S orbital in each energy level. This means that there are two electrons in each S orbital in each energy level. Conversely, the P orbital begins in the second energy level, n=2, and there are three P orbitals per energy level. This means that there are a total of six electrons in the P orbitals per energy level. Finally,

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Finally, there are D orbitals beginning in the third energy level, N=3, and in each energy level there are five D orbitals. This means that there are 10 electrons in D orbitals per energy level. This correlates perfectly with the periodic table. The first two rows of metals correlate with the two electrons in S orbitals in each energy level, the six rows of non-metals correlate with the six P electrons, and the 10 rows of transition metals correlate with the 10 D electrons. This creates a chart that looks like this:1

Section 4

S, P, and D blocks

15

Review Questions

1. Which of these elements has the greatest atomic radius:

a. N, Nitrogen

b. F, Fluorine

c. Hg, Mercury

2. Which of these elements is the most electronegative:

a. N, Nitrogen

b. F, Fluorine

c. Hg, Mercury

3. Is the following element in the S, P, or D block. How many valence electrons does that element have? C, Carbon

a. S Block, 4 Valence Electrons

b. D Block, 10 Valence Electrons

c. P Block, 4 Valence Electrons

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Question 1:

Correct answer was Hg, Mercury, C. Recall that atomic radii increases as you move down a row and to the left across the periodic table.

Question 2:

Correct answer was b. F, Fluorine. Re-call that electronegativity increases as you move up a row and to the right across the periodic table.

Question 3:

Correct answer was c. P block and 4 Valence Electrons. Recall that the non-metals are the P block and if you count over Carbon has two S electrons and 2 P electrons making a total of 4.

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1. A BRIEF HISTORY OF THE DEVELOPMENT OF PERIODIC TABLE. Western Oregon University. https://www.wou.edu/las/physci/ch412/perhist.htm (accessed, 26 November 2013)

2. The Chemical Elements Song. Music by Sir Arthur Sullivan. http://www.youtube.com/watch?&v=K8eT-k4f7_8 (accessed 21 November 2013)

3. Early History of the Periodic Table Quiz. http://www.ck12.org/chemistry/Early-History-of-the-Periodic-Table/quiz/Early-History-of-the-Periodic-Table-Quiz/ (accessed 21 November 2013)

4. What’s an Ion? Tyler DeWitt. https://www.youtube.com/watch?v=WWc3k2723IM (accessed 26 November 2013)

5. Groups of the Periodic Table. OER Commons. http://www.oercommons.org/courses/chemistry-groups-of-the-periodic-table/view (accessed 26 November 2013)

6. Periodic Trends. cK-12. http://www.ck12.org/section/Periodic-Trends-%253A%253Aof%253A%253A-The-Periodic-Table-%253A%253Aof%253A%253A-CK-12-Chemistry-Intermediate/ (accessed 21 November 2013)

References

Image Number

Date Accessed

Title and or Photographer

URL

1 Nov. 21Pictures of Famous Chemists

http://chemistry.about.com/od/historyofchemistry/ig/Pictures-of-

Famous-Chemists/Dmitri-Mendeleev.htm

2 Nov. 21Wikimedia Commons

ghttp://commons.wikimedia.org/wiki/

File:Eight_category_periodic_table_(Mk2).pn

3 Nov. 21 flickr http://www.flickr.com/photos/mrspugliano/5351057718/

4 Nov. 21Periodic Trends

http://www.ck12.org/section/Periodic-Trends-%253A%253Aof

%253A%253A-The-Periodic-Table-%253A%253Aof%253A

%253A-CK-12-Chemistry-Intermediate/

5 Nov. 26UC Davis

Chem Wiki

http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Descriptive_Chemistry/Periodic_Table_of_the_Elements/Periodic_Trends

6 Nov. 26 Wikipediahttp://ja.wikipedia.org/

wiki/周期表