SCH3U Periodic Table Trends pg. 1/7

Periodic Table Trends

by Steve HallSCH3U

for Vance McPhersondate: March 20th/2013

SCH3U Periodic Table Trends pg. 2/7

IntroductionThe periodic table is arranged according to periodic law. It displays chemical elements organized by their atomic numbers, electron configurations and recurring chemical properties. Two of these recurring chemical properties will be looked at in this report1.

The periodic table was really revolutionized by a Russian chemist named Dmitri Mendeleev. He started his periodic table before electrons were discovered, so his version is no longer used today, but the periodic table we know and appreciate is the way it is because of Mendeleev. Dmitri Mendeleev was no ordinary chemist – he was a genius. He was so genius, when other chemists claimed to have discovered a new element, he could dispute them, and prove them wrong without even seeing there element, solely because he understood the periodicity of elements in our environment.

In this report, the periodicity of atomic radius and electronegativity is examined for the first 18 elements on today's periodic table. It's all thanks to Mendeleev that we can look at a sheet of paper with the table printed on it and obtain so much knowledge and only a small fraction of this knowledge will be applied in this report. There are so many hidden secrets on the periodic table. It truly is fascinating that the world around us all fits in to one chart!

Task1. Using online or print resources, research the following variables for the first eighteen elements

of the periodic table (i.e. hydrogen — argon):

a. Electronegativity (measured in Pauling units) b. Atomic Radius

2. Using Microsoft Excel or another comparable spreadsheet, generate a graph that shows the relationship between electronegativity and radius. Your independent axis should be “atomic number” and should move sequentially from 1 to 18. Because atomic number is a discrete variable, you should be generating a bar graph. Each atomic number will show both variables. This may be done as a three-dimensional graph, an overlapping bar graph or another creative means. Since you are graphing two variable with different units, your graph needs a separate scale for each. Your graph needs to have two y-axis, one on the left, and one of the right. One axis will be for Electronegativity, and one will be for Atomic radius. Be sure that your graph has a title, axis labels, and units.

3. Produce a report to summarize your work. Your report should contain:a. A brief introduction to the report. b. A table showing your values you have researched for Electronegativity and Atomic

Radius c. The graph showing the relation ship between Electronegativity and Atomic Radius d. A written, 250 word, analysis of your graph. Your analysis should include several trends

from the graph, several examples to support these trends, exceptions to the trends, and a thorough explanation as to why the trends occur.

1 Electronegativity & Atomic Radius

SCH3U Periodic Table Trends pg. 3/7

ObservationsThese are the results I found through online resources:

Electronegativity ValuesAtomic # Element Name Value

1 Hydrogen (H) 2.20

2 Helium (He) 0

3 Lithium (Li) 0.98

4 Beryllium (Be) 1.57

5 Boron (B) 2.04

6 Carbon (C) 2.55

7 Nitrogen (N) 3.04

8 Oxygen (O) 3.44

9 Fluorine (F) 3.98

10 Neon (Ne) 0

11 Sodium (Na) 0.93

12 Magnesium (Mg) 1.31

13 Aluminum (Al) 1.50

14 Silicon (Si) 1.80

15 Phosphorus (P) 2.19

16 Sulfur (S) 2.58

17 Chlorine (Cl) 3.16

18 Argon (Ar) 0

Atomic Radius ValuesAtomic # Element Name Value

1 Hydrogen (H) 53pm2

2 Helium (He) 31pm

3 Lithium (Li) 167pm

4 Beryllium (Be) 112pm

5 Boron (B) 87pm

6 Carbon (C) 67pm

7 Nitrogen (N) 56pm

8 Oxygen (O) 48pm

9 Fluorine (F) 42pm

10 Neon (Ne) 38pm

11 Sodium (Na) 190pm

12 Magnesium (Mg) 145pm

13 Aluminum (Al) 118pm

14 Silicon (Si) 111pm

15 Phosphorus (P) 98pm

16 Sulfur (S) 88pm

17 Chlorine (Cl) 79pm

18 Argon (Ar) 71pm

2 These values are in picometers (pm). They are accurate within 5 pm.

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Graph 1: Electronegativity

Graph 2: Atomic Radius

SCH3U Periodic Table Trends pg. 5/7

Graph 3: Comparison Graph

AnalysisFrom the graph above, we can see many trends. On the periodic table, elements #1-2 are considered, “period 1”. A period is a row on the periodic table. Elements #3-10 are considered “period 2”, and elements #10-18 are considered “period 3”, and so on, adding on 8 each time.

An exception to this trend, as you may have already spotted is period one. Hydrogen and Helium are all alone up in period 1. These two elements will show that they have exceptions later on as well. By looking at the graph, you will notice that electronegativity gets higher as atomic radius gets smaller each period. Without the knowledge that periods exist on the periodic table, this graph looks quite choppy and trends may be hard to spot. They are there though! The line representing atomic radius crosses the bars representing electronegativity, as if it is drawing an X. This pattern is called a trend.

But why is this happening? Why does electronegativity get larger while atomic radius gets smaller? Believe it or not, this doesn't just occur. There is a scientific explanation! Across the row (period) on the periodic table, nuclear charge is increasing and electrons are pulling tighter and tighter in towards the nucleus. We know the nuclear charge is increasing, because the numbers of neutrons is determined by the atomic number, and the atomic number increases as you progress through the table.

The electrons are pulling closer into the nucleus, because protons (that have positive charges) are found in the nucleus, and electrons have negative charges. It's like with magnets! The positives and negatives attract. If that's too difficult, think of it like this – because the nuclear charge is higher, the electrons just love that so much, they want to be closer to the nucleus to experience the awesomeness! When the electrons pull tighter towards the nucleus, the atomic

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 180

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Electronegativity and Atomic Radius Comparison

Steve Hall - SCH3U - March 20/2013

ElectronegativityAtomic Radius

Atomic Number

Ato

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Ra

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(pm

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Ele

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SCH3U Periodic Table Trends pg. 6/7

(Analysis continued)radius decreases, and this is the relationship we see on the graph above!

Our exceptions in period 1 aren't as confusing as you think they may be. Period 1 is only made up of 2 elements – one is hydrogen, and that has an electronegativity of 2.20. The second element in period 1 is helium, which is a noble gas. Noble gases always have an electronegativity of 0, because they are unreactant. You can also see values of 0 on the graph for element #10, neon and #18, argon. These are also noble gases. But we can also notice the exception of hydrogen as a group 1 element. Elements in group 1, otherwise referred to as column 1, include #1, #3 and #11. When the period restarts, the elements in group 1 have low negativity and high atomic radius – usually. For hydrogen, it has a low atomic radius and a high electronegativity. This is because hydrogen is the first element on the table; meaning, 1 proton, 1 neutron, 1 electron.

To understand this, I like to think of each element on the table like a school. At this school, there are uniforms that are mandatory to wear, however hydrogen likes to be different. If the uniform is a blue blazer, hydrogen comes to school wearing a pink t-shirt. Why? Simply because, young hydrogen is programmed differently than the rest of the students at our Periodic Table school. How? Because hydrogen only has 1 proton and 1 electron, the nuclear charge is not very strong – in our school analogy, we could think of this as the student, hydrogen is a little slow. With a weaker nuclear charge, the sole electron on hydrogen likes to float around, not sticking to the proton very tightly, making the atomic radius larger – maybe, if hydrogen were a person, they'd be a little bit bigger. If we say that the first 18 elements is a class of 18 students, hydrogen is the only student in the class who is not conforming, however hydrogen is not alone in the entire school.

ConclusionBefore I had even constructed the graph, I noticed some trends. I found that the atomic radius seemed to be much larger for the elements in group 1 and 2, and decrease as the elements move to the right along the table. At first glance, I was thinking by means of mentally organizing the elements by groups, however I soon realized it is much easier to notice the trends by period. By creating this report, I was able to develop a deeper understanding of some different periodic trends, and deeper understanding of the periodic table, leads to a deeper understanding of the whole world around us!

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BibliographyAtomic radius for all the elements in the periodic table. (n.d.). Retrieved April 7, 2013, from

Periodic Table website: http://periodictable.com/Properties/A/AtomicRadius.v.html

Chan, M. (2008). Chemistry 11, university preparation (SCH3U) (Ontario ed.). Mississauga, ON: Castle Rock Research.

Clancy, C. (2010). McGraw-Hill Ryerson chemistry 11. Toronto: McGraw-Hill Ryerson.

Haberer, S., & DiGiuseppe, M. (2011). Nelson chemistry 11: University preparation. Toronto, Ont.: Thomson/Nelson.

The periodic table [Show #4]. (2013, March 4). Crash course chemistry. Podcast retrieved from http://www.youtube.com/watch?v=0RRVV4Diomg

Salem, M. (2010). Pauling electronegativity. Retrieved April 7, 2013, from ChemWiki website: http://chemwiki.ucdavis.edu/Physical_Chemistry/Atomic_Theory/Pauling_Electronegativity

Scerri, E. R. (2007). The periodic table: Its story and its significance. Oxford: Oxford University Press.