Tuesday, April 26, 2011

Periodic Table Families

PERIODIC TABLE FAMILIES!





Families. We all have them. Sometimes, they may drive us crazy. But love them or hate them, we're stuck with the ones we've got, so we have to stick with them for what they're worth.

Just like us, the periodic table can be grouped into certain families as well! These families are:



Alkali metals: Shown as the yellow strip on the far left, alkali metals display properties such as high density levels, a single valence electron, low ionization energies, and a large atomic radii.

Alkali earth metals: Shown as the bright, bright blue strip next to the alkali metals, alkali earth metals have two electrons in their outer shells, low electronegativities, and slightly smaller atomic radii than the alkali metals.

Transition metals: These metals form the huge block between the alkali earth metals and the metalloids. They have high melting and boiling points, are malleable, and are good conductors of electricity.

Metalloids: These form a staircase consisting of boron, silicon, germanium, arsenic, antimony, and tellurium. Polonium is still under debate regarding its status as a metalloid. Metalloid properties vary widely. They have differing boiling and melting points, and are good semi-conductors.

Halogens: Halogens, as shown by the strip of pale yellow, are highly reactive elements. They display high levels of electronegativity, and all have seven valence electrons.

Noble gases: The orange family on the far right, noble gases tend to be very stable because they have full outer shells. Noble gases have low boiling points and rarely lose or gain electrons. They display low electronegativity.

Rare earths: These are the two sky blue rows at the very bottom, the Lanthanide series and the Actinide series. These metals are good conductors, are usually silvery in colour, and have high densities.



And now here's a nice poem by Michael Carungi!

Carbon, the Champion

Carbon is the element that is the basis
Of all organic life in all places
It can bond with elements, that's a fact
Over ten million compounds to be exact
When united with a substance like air
Carbon dioxide is created, which is used to prepare
The growth of plants. And when Carbon is combined
With Hydrogen, fuels are made. Diamonds and Graphite are a kind
Of Carbon, where Diamonds are the hardest ever known
And a softer substance than Graphite is unknown
Carbon also has the highest melting grade
And Carbon cannot be artificially made.
Yes, Carbon is truly a great thing
And it should be declared the elemental king.



UNTIL NEXT TIME!

Valence Electron Predictions

Valence Electrons!

As you may recall from previous science courses, valence electrons are the electrons that are on the outermost energy level of an atom.

Valence electrons are the ones that take part in chemical reactions. The more unstable an atom is, the more likely it will gain or lose electrons to become stable.



Take a neutral sodium atom, for example. It has eleven electrons, two on the first energy level, eight on the second, and one on the last one. Sodium in this case has an open shell, because its outermost shell is not completely filled.



How how sad it is, to be that lonely little valence electron hanging out all by itself! Poor little particle! Won't anyone love him for who he is? He just wants to be LOVED! He doesn't need much at all, really, just someone out there to care for him, and he'll care for them in return too! Um...*cough* I mean...okay, anyway...moving on...




Noble gases do not gain or lose electrons easily. This is because they typically have closed shells, which mean that their outermost shells are filled up.

Take argon, for instance. See how all the available spaces are taken up by electrons?




Writing Core Notation to Figure out the # of Valence Electrons

Here's a trick for writing electron configurations that can save you a lot of time. Let's say you're writing the configuration for an ion of manganese - Mn 2+ .

A neutral atom of Mn has 25 electrons, and Mn2+  will have 23, since it lost two to gain a +2 charge. The electron configuration of Mn2+  will be 1s22s22p63s23p64s23d3

Now look closely at the noble gases. Notice how the first part of the configuration of argon (1s22s22p63s23p6) is the same as Mn2+. In this case, we can substitute the first part of Mn2+   that contains all the same configuration as Ar for the notation of Ar itself!

So now we have [Ar]4s23d3.

To find all the valence electrons, count up the # of electrons that was NOT included in the core. Do NOT count filled d- or f- shells.

Mn2+  has 5 valence electrons. Amazing!

Looking for further help? Check out this informative website!

History of Periodic Table

DID you know that there has been a prodigious amount of change in the way periodic table arranges?




In the Beginning
the first scientific discovery of an element occurred in 1649 when Hennig Brand discovered phosphorous. During the next 200 years, a vast body of knowledge concerning the properties of elements and their compounds was acquired by chemists. By 1869, a total of 63 elements had been discovered. As the number of known elements grew, scientists began to recognize patterns in properties and began to develop classification schemes.
Law of Triads
In 1817 Johann Dobereiner noticed that the atomic weight of strontium fell midway between the weights of calcium and barium, elements possessing similar chemical properties. In 1829, after discovering the halogen triad composed of chlorine, bromine, and iodine and the alkali metal triad of lithium, sodium and potassium he proposed that nature contained triads of elements the middle element had properties that were an average of the other two members when ordered by the atomic weight (the Law of Triads).
Law of Octaves
John Newlands, an English chemist, wrote a paper in 1863 which classified the 56 established elements into 11 groups based on similar physical properties, noting that many pairs of similar elements existed which differed by some multiple of eight in atomic weight. In 1864 Newlands published his version of the periodic table and proposed the Law of Octaves (by analogy with the seven intervals of the musical scale). This law stated that any given element will exhibit analogous behavior to the eighth element following it in the table.
Who Is The Father of the Periodic Table?
There has been some disagreement about who deserves credit for being the "father" of the periodic table, the German Lothar Meyer (pictured here) or the Russian Dmitri Mendeleev. Both chemists produced remarkably similar results at the same time working independently of one another. This consisted of about half of the known elements listed in order of their atomic weight and demonstrated periodic valence changes as a function of atomic weight. Unfortunately for Meyer, Mendeleev's table became available to the scientific community via publication (1869) before Meyer's appeared (1870)!





Discovery of the Noble Gases
In 1895 Lord Rayleigh reported the discovery of a new gaseous element named argon which proved to be chemically inert. This element did not fit any of the known periodic groups. In 1898, William Ramsey suggested that argon be placed into the periodic table between chlorine and potassium in a family with helium, despite the fact that argon's atomic weight was greater than that of potassium. This group was termed the "zero" group due to the zero valency of the elements. Ramsey accurately predicted the future discovery and properties neon.
Atomic Structure and the Periodic Table
Although Mendeleev's table demonstrated the periodic nature of the elements, it remained for the discoveries of scientists of the 20th Century to explain why the properties of the elements recur periodically.

In 1911
Ernest Rutherford published studies of the scattering of alpha particles by heavy atom nuclei which led to the determination of nuclear charge. He demonstrated that the nuclear charge on a nucleus was proportional to the atomic weight of the element.

 This charge, later termed the atomic number, could be used to number the elements within the periodic table. In 1913, Henry Moseley (see a picture) published the results of his measurements of the wavelengths of the x-ray spectral lines of a number of elements which showed that the ordering of the wavelengths of the x-ray emissions of the elements coincided with the ordering of the elements by atomic number. With the discovery of isotopes of the elements, it became apparent that atomic weight was not the significant player in the periodic law as Mendeleev, Meyers and others had proposed, but rather, the properties of the elements varied periodically with atomic number.


PERIODIC LAW: properties of chemical elements recur periodically when the elements are arranged from lowest to highest atomic #s.The question of why the periodic law exists was answered as scientists developed an understanding of the electronic structure of the elements beginning with Niels Bohr's studies of the organization of electrons into shells through G.N. Lewis' (see a picture) discoveries of bonding electron pairs.
The Modern Periodic Table
The last major changes to the periodic table resulted from Glenn Seaborg's work in the middle of the 20th Century. Starting with his discovery of plutonium in 1940, he discovered all the transuranic elements from 94 to 102. He reconfigured the periodic table by placing the actinide series below the lanthanide series. In 1951, Seaborg was awarded the Nobel Prize in chemistry for his work. Element 106 has been named seaborgium (Sg) in his honor.


If you are truly passionate about this, you can also check out these very educational video by BBC!
They summarizes the history from the first discovery to the first organizing to the modern periodic table we know now...

http://www.youtube.com/watch?v=nsbXp64YPRQhttp://www.youtube.com/watch?v=25lprEvoFJ8&feature=related
http://www.youtube.com/watch?v=25lprEvoFJ8&feature=related
http://www.youtube.com/watch?v=hHL80A93lCA&feature=related

Wednesday, April 20, 2011

Electron Configeration

Electronic Configeration = orbitals electron occupy + # of electrons in each orbital.
History: Bohr's proposal-electrons moves from one orbital to another when emit or absorb energy.
Energy level= amount of energy an electron can possess( n)
Ground State: all e- in lowest possible energy level
Excited State: 1 or more e- in energy level other than lowest available level

( orbital: region occupied by an electron in a specific energy level.-> S, P, D, F
( shell: set of all orbitals w same n-value. (n) = energy level
( subshell: set of orbitals of same type.

Comparing Energy level of Hydrogen to Polyelectronic atom


H (1S1)   1 e-
He ( 1S 2)  2 e-
Be (1S2 2S2)  4 e-

Orbital:
n=1 : only s-type possible
n=2: s, p-types are possible
n=3: s, p, d-types are possible
n=4: s, p, d, f-types are possible

Subshell:
s-subshell include 1 s-orbital
p-subshell include 3 p-orbitals
d-subshell include 5 d-orbitals
f-subshell include 7 f-orbitals



The diagram above shows how s, p, d, f are distrbuted on the periodic table for each element, and we can use this diagram to understand and write the electronic configeration.

TWO ESSENTIAL RULES:

1. electrons MUST be added to lowest energy orbital 1st.
2. maximum of 2 e- in each orbital:
 2 e- in s-type subshell, 6 e- in p-type subshell, 10 e- in d-type subshell, 14 e- in f-type

E-Configeration for Neutral atoms
like Na, P, Ca, Fe, ......

1.how many e-?
2.each e- has 1 upward and 1 downward arrow

ex. Silicon, Si has 14 e-.

Look at the diagram below and starts with the lowest energy level, then keep adding until it fulfills the all # of e-.

Si ( 1s2 2s2 2p6 3s2 3p2)

Exercise:

a)Mn b) Co c) Rb d) P

Answer:
a) 1s2 2s2 2p6 3s2 3p6 4s2 3d5
b) 1s2 2s2 2p6 3s2 3p6 4s2 3d7
c) 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1
d) 1s2 2s2 2p6 3s2 3p3

Core notation: simplifies the work by replacing a set of configeration with the nearest noble gas with less atomic number.

try those with the same exercise above, did you get the answer?
a) [Ar] 4s2 3d5
b) [Ar] 4s2 3d7
c) [Kr] 5s1
d) [Ne] 3s2 3p3

E.Configeration for ions

negative: add e- (same as charge) to last UNFILLED subshell, where neutral atom left off.

Ex. P 3-
1s2 2s2 2p6 3s2 3p3 -> 1s2 2s2 2p6 3s2 3p6

positive: remove e- from largest n-value, remove p-electron before s-electron before d-electron.

Ex. Sn 2+
[Kr]5s2 4d10 5p2 -> [Kr] 5s2 4d10

I believe simple rule following like this won't preplex all of you!
Thanx for comin!

Monday, April 18, 2011

April 18, 2011

Hello, hello, hello! What a beautiful, nice sunny day it is! Today we had no rain at all with the sun shining above! So let's get straight down to what we learned today..... Today it was basically a review of what we learned in grade 9, ahhh grade 9 seems so long ago, gosh, ok right getting off topic here..... today we learned about......

Atomic Structure!

- The subatomic particles are: protons, neutrons and electrons.
 ˜Proton:
Symbol = (we use the P)
Relative Mass = 1
Electric Charge = +1
Location in the Atom = nucleus
 ˜Neutron:
Symbol =
Relative Mass = slightly bigger than 1
Electric Charge = 0
Location in the Atom = nucleus
 ˜Electron:
Symbol =  (we use the E)
Relative Mass = 0
Electric Charge = -1
Location in the Atom = cloud surronding the nucleus

- In a Neutral atom, # of Protons = # of Electrons

Atomic Number (Z): The proton number
- The Atomic Number (Z) is the number of protons found in the nucleus of an atom.
- Atoms have no overall electric charge (i.e. charge of atom is zero).
- Atomic Number = # of protons = # of electrons

Ions:
- Atoms that have gained or lost electrons are called ions.
- An ion is an electrically charged atom (or groups of atoms).
- Negatively-charged ion = anion
- Positively-charged ion = cation
- For Ions; # of electrons = protons - charge

Mass Number (A):
- Is the total number of protons and neutrons or atomic mass number.
- Atomic Number = the # of protons
- Atomic Mass = # of protons + # of neutrons
- Number of neutrons = Mass Number - Atomic Number
- Mass Number = # of protons + # of neutrons

Atomic Mass:
- The average mass of an element's isotopes.
- The atomic mass is very close (not exact!) to the mass number.
- # of neutrons = Mass Number - Atomic Number
                         Atomic Mass - Atomic Number
- The atomic mass is an average! The mass number is usually calculated by rounding the atomic mass to the nearest whole number.

Isotopes:
- Are atomic species having the same atomic number (protons) but different atomic masses/mass numbers (neutrons). Basically, same # of protons and electrons, but different # of neutrons.

Whew! Alot of information but pretty simple to comprehend, which is a very good thing :) So now let's give you some important visuals!










Hope those are helpful, and now here are some worksheets & extra information for you:
1) http://www.sciencejoywagon.com/chemzone/02atomic-structure/
2) http://misterguch.brinkster.net/propertyworksheets.html
3) http://docs.google.com/viewer?a=v&q=cache:Svl1HS3qzfsJ:misterguch.brinkster.net/001_021.doc+atomic+structure+worksheet&hl=en&gl=ca&pid=bl&srcid=ADGEESj_WYrtiEN2lX55CTrVQlm1hc7YmKY1mVbgw1DoKBPwfd7ZkvmnBtHXM9MonGdgMHr7rYPbP_zspbkgYZtxil2dk5ld9UqPcFm79Mukr5YOnQD-v3EXpsaki74QhGzie3QH_Cry&sig=AHIEtbTL6KdKPbx4-wFOQzdx-a1ZI3Et9g&pli=1
4) http://cmsweb1.loudoun.k12.va.us/52820831134912597/lib/52820831134912597/Atoms%20and%20Atomic%20Theory/Homework/ws.atomic.20structure.20set.pdf
5) http://www.allaboutcircuits.com/worksheets/atomic.html
6) http://staff.fcps.net/jswango/unit2/atomic_structure/Basic%20Atomic%20Structure%20Worksheet.pdf
7) http://chemistry.about.com/library/weekly/blatomquiz2.htm
8) http://www.softschools.com/quiz_time/chemistry/atomic_structure/theme81.html

Last but not least, here are some youtube videos:
1) http://www.youtube.com/watch?v=7ohfJ9ku8gc&feature=fvwrel
2) http://www.youtube.com/watch?v=WWxnZK_g5ug
3) http://www.youtube.com/watch?v=Z6Y4Ffod1hQ&feature=related

Thanks for reading & have a great long weekend! Wooooooooooo!!! :)

Thursday, April 14, 2011

[History of the Atom]

|We are starting a new unit today called the Atomic Theory.|
|This is the start of atom and where ideas of atoms emerged...|
|Why do you think ancient philosophers were so interested in the phenomenon of atoms? |
|Perhaps they were curious about the foundation of all matters and that was when they came up with atom...|

  • Aristotle became the first to propose that all matter consists of four elements either
|EARTH|  |WATER| |FIRE| OR |AIR|
Aristotle: http://www.iep.utm.edu/aristotl/
  • Alchemist Brought Au to Earth by changing the mechanics of metal!
  • The Four Element theory lasted for about 2000 years!
  • Democritus proposed that atom = indivisible particles though this was not a testable theory and merely a model.=[ There was also no discovery of nucleus, proton or electrons. Thus, it cannot be used to explain chemical reactions
Alchemist full metal image
  • Lavoisier started 1st version of Law of Conservation of Mass & Law of Definite Proportions.

Law of Definite Proportion means that the % of an element on a compound will never change!
  • Proust proposed:  even if compound are broken down, the ratio in the compound would still apply to the products.
  • Dalton provided a vision of an atom = solid, sphere and his experiments and discoveries were based on the Law of Conservation of Mass
  • Dalton's Law #1: Elements made up of atoms
  • Dalton's Law #2: All atoms of a element are identical.
  • Dalton's Law #3: atoms are distinguished by relative weight
  • Dalton's Law #4: Atom(of different element) + Atom(of different element) = chemical Compound, with same # of same types of atom
  • Dalton's Law #5: Atoms are indivisible, non-destructable and they cannot be created.
A new revoluntion started when another chemist proposed his hypothesis stating that there are both positive and negative particles inside an atom.

Thomson gave new characteristics to an atom: they are solid spheres with negative particles embedded (electrons) and positive particles (protons). He figured out the mass of electron, 9.10938188 x 10 -28 grams.



Adding to Thomson's discovery, RUtherford explained that all the positive particles gathers in the dense centre of an atom. They electrons are outside of the dense positive center. His model is called the planetary model.

this is the famous GOLD LEAF experiment provides evidence for the positive centre of an atom.

Niels Bohr contributed to this RACE of ATOM most notably for discovering the Electrons in specific energy level or shells outside the nucleus.



BOHR diagram of atoms 
After evolutionary change in understanding of atom, our knowledge of an atom today is the smallest
particle of an element that reatains the properties of element. There are 3 kinds of particles called subatomic particles: e, p, n


http://www.youtube.com/watch?v=h0UllT0DE7s&feature=related
This is an exellent video presenting the historical timeline of the atomic theory!
ENJOY~

Tuesday, April 5, 2011

April 5th

WELCOME BACK EVERYONE! Hope you all had a nice and relaxing spring break!

TODAY WE'RE GOING TO BE DOING PERCENT YIELD AND PERCENT PURITY!

It's the last thing before our test! :D


It's sad, isn't it? :( Okay, let's get on with things!

Percent Yield

 
The first thing we'll be covering is percent yield! If you recall from the last day's lab, percent yield is calculated using this formula:

% Yield:

actual mass produced (in grams)           x     100%
theoretical mass produced (in grams) 
Now today we'll be doing problems with this formula.


Question: Zinc reacts with hydrogen chloride to form zinc chloride and and hydrogen gas. If 23.09g of hydrogen chloride was used in this reaction, and 0.44g of hydrogen gas was formed, what is the percent yield?

Use the following steps to solve this question:
1. Write the equation given.


Zn + HCl → H2 + ZnCl2
 
2. Balance it!

1Zn + 2HCl → 1H2 + 1ZnCl2


3. Now that you have your mole ratio, you need to draw in your mind a mental map of where you are and where you want to go. You want to get from grams of hydrogen chloride to grams of hydrogen gas to find the THEORETICAL yield of hydrogen gas in the equation.

23.09g HCl x 1 mol HCl / 36.5g HCl x 1 mol H2/ 2 mol HCl x 2g H2/ 1 mol H

= 0.6326g H2 with sig figs = 0.63g H2


Now we'll use the percent yield formula to calculate, well, percent yield!


% Yield:

actual mass produced (in grams)          x 100%
theoretical mass produced (in grams) 


% Yield:

0.44g    x  100%
0.63g

= 69.8%, with sig figs = 70.%

Percent Purity




Percent purity is a lot like percent yield. The formula for percent purity is:




Mass (grams) of pure substance                 x 100%
Mass (grams) of total (impure) substance


Question: If a mass of gold ore weighs 56.2g, and contains 12.2g of pure gold, what is the percent purity?


Simply plug the variables into the formula to determine the purity.


12.2g  x 100%
56.2g


= 21.7% purity
And there you have it! Percent purity and percent yield!
 GOOD LUCK ON THE TEST EVERYONE!


Some brave soul made a percent yield song for his chemistry class:



"♫Percent yield...the most important thing you'll ever learn!"