Electron Dot and Lewis Diagrams

So for todays class we learned about the Electron Dot and Lewis Structures. It was mainly review with a few minor new things. I will keep this short, and sweet! Enjoy :)

These are a couple of ways you can draw bohr diagrams.....but before i show you, just keep in mind, that when you draw dots on around the symbol of the specific element, you would have to know the number of valence electrons of the required element.

Here's the example.....



This is a breif video about how to make Lewis Structures.

http://www.youtube.com/watch?v=6xTY63KqACE&feature=player_embedded

Here are the steps on making a Lewis Structure;

Draw the atoms on paper and put dots around them to represent valence electrons of the atom. Be sure to have the correct number of electrons.

If the species is an ion, add or subtract electrons corresponding to the charge of the ion. Add an electron for every negative (-) charge, and subtract an electrons for every positive (+) charge.

Consider bonding between atoms by sharing electrons, some may come from one atom.

If possible, apply the octet rule to your structure. Some structures don't obey the octet rule, but explain why.

Assign formal charges to atoms in the structure

Check out this website and try out the problems !

http://misterguch.brinkster.net/PRA017.pdf

History of the Periodic Table

Greetings!

Today we shall be investigating the history of the periodic table!

Excuse me while I grab Micheal J. Foxx for our read today.

In the beginning

Chemists were starting to discover a lot of elements (62 by 1863).

They needed some kind of organization.

William Odling

• in 1857 separated known elements into 13 groups based on their physical and chemical properties

John Newlands

• in 1863 showed that by assigning Hydrogen an arbitrary mass of 1 and ordering known elements by masses, every 8th element shared comment set of properties. (Law of Octaves)
• this failed to predict elements and constantly changed the order the elements

Dimitri Mendeleev

Published method organizing the elements according to their masses and properties

• Showed elements listing according to masses and certain properties recurred periodically 
• broke list into series of rows/periods and columns/groups
• placed elements in certain groups based on properties in spite of contrary indications by its mass

He left gaps in his table, proposing that there where elements yet to be discovered

This allowed chemists to organize, understand data and predict new properties

Modern Periodic Table

Organized by atomic number rather than mass
Periodic Law summarizes the periodic table

• properties of the chemical elements recur periodically when the elements are arranged from lowest to highest atomic numbers

Major divisions of the periodic table are

• periods: set of all elements in a given row across the table
• groups/families: set of all elements in a given column going down the table

Chemical Families

• Metal and NonMetal Properties

• Metalloids
• or semiconductors are non-metals with electrical conductivity that increase with temperature
• have properties resembling metals more than non-metals
• the difference between metals and metalloids is
• metals conductivity decreases with increasing temperature
• metalloids conductivity increase with increasing temperature

Now that you are familiar with the periodic table, let us celebrate with a song!

Trends on the Periodic Table

Greetings lowly visitors

I see you are not up to date on your periodic trends

I scoff in your general direction! Look at that row! It's so last season.

Periodic Trends

• tendencies of certain elemental characteristics to increase or decrease as one progresses along a row or column of the periodic table of elements
• there are several trends that you must be able to describe to be trendy within this circle!
• metallic properties
• atomic radius
• ionization energy
• electronegativity
• reactivity
• ion charge
• melting/boiling point
• density

Metallic Properties

• properties change from metallic to non-metallic from left to right
• become more metallic going down a family in the periodic table

Atomic Radius

• Decrease going across row from left to right
• Increase going down a group
• as the number of protons in the nucleus of the atom increases, there is a greater force of attraction for the electrons in the shell and the distance between the electrons and nuclease decrease

Reactivity

• metals and non-metals show different trends
• when the metals move down and right it is more reactive
• when non-metals move left and up it is more reactive

Ion Charge

•  element charges depend on their group

Melting Point and Boiling Point

• elements in the centre of the table have the highest melting point
• noble gases have the lowest melting point
• start from the left and moving right; melting point increases until the middle of the table

Ionization Energy

• the energy needed to completely remove an electron from an atom
• increases going up and to the right
• all noble gases have ionization energy
• helium has the highest ionization energy and francium has the lowest
• opposite trend from the atomic radius
• measured in KJ/mol
• can have 1st ionization energy, 2nd ionization energy
• refer to the removal of more than one electron

Electronegativity

• refer to how much atoms want to gain electrons
• same trend as ionization energy
• tendency of an atom to attract electrons from a neighboring atom
• if atom has high EN
• strongly attract electrons and may completely remove them
• also strong attracted to own valence electrons=harder to remove
• if atom has low EN
• little tendency to remove electron from neighbor
• also has small attraction to own electrons
• low ionization energy=easily removable

VOILA! NOW AREN'T YOU ALL FANTABOULOUS READERS?!

LOOK AN INTERACTIVE PERIODIC TABLE

Learn from it! Understand it!

Electronic Structure of the Atom

Compliments to your arrival, readers!

We have an extremely structured read for you today!

Not getting the electronic pun?

YOU WILL SOON!

Electronic Configuration

• is the notation that describes the orbitals that electrons occupy
• also shows total number of electrons in each orbital
• helps us understand the structure of the periodic table of elements

Niels Bohr

• proposed electrons existed in specific energy levels
• when it absorbs/emits specific amount of energy it instantaneously moves from one orbital to the next

Energy Level: amount of energy an electrong of an atom can possess with 'n' the number energy levels

Quantum of Energy: energy difference between two particular energy levels

Ground State: when all electrons of an atom are in the lowest possible energy

Excited State: when one ore more of an atom's eletrons are in energy levels other then the lowest available level

Orbital: region of space occupied by an electron in a particular energy level 

Shell:  set of all orbitals having the same 'n' value

Subshell: set of orbitals of the same type

Now let's get into the meat of the lesson today!

Orbitals

• are split into 4 different types (s, p, d, f)
• each subshell consists of:
• 1 s-orbital
• 3 p-orbital
• 5 d-orbital
• 7 f-orbital
• maximum of 2 electrons can be placed into each orbit
• the maximum number of electrons in each subshell is
• 2 s-subshell
• 6 p-subshell
• 10 d-subshell
• 14 f-subshell

Electronic Configuration

This is how the orbitals are filled in for neutral atoms

1. Always start with the lowest energy level first
2. Figure out how many electrons you have (neutral atom = atomic number)
3. Start at the lowest energy level (1s) and add until nothing is left
4. Each electron has an opposite spin designated by upward and downward arrows

An example is Carbon. The last line of the picture show electronic configuration. Carbon has an atomic number of 6 = 6 electrons. The last two are not paired because when electrons occupy orbitals of equal energy, they don't pair up until they have to. 

• A good analogy of this is: when you're sitting on a bus, you don't sit beside another person until all the empty rows are taken up.
• The written form of this is 1s2 2s2 2p2

Writing Electron Configurations for Ions

For Negative Ions

• Add electrons (equal to charge) to the last unfilled subshell, starting with where the neutral atom left off

For Positive Ions

• Start with the neutral configuration, remove electrons from the outer most shell first
• If there are electrons in both the s and p-orbitals of the outermost shell
• Electrons in p-orbitals should be removed first

Core Notation

• The set of electrons for an atom can be divided into two subsections (boy do we canadians love dividing everything into sections, and even SUB-sections!)
• the core electrons
• set of electrons with configuration of the nearest noble gas before it (above it)
• normally take part in chemical reaction
• the outer electrons
• consist of all electrons outside the core
• is a way of showing the electron configuration in terms of the core and the outer electrons

1. Locate the atom and note the noble gas above the element
2. Replace the part of the electronic configuration that has the configuration of the noble gas with the noble gas symbol in brackets
3. Follow the core symbol with the electron configuration of the remaining outer electrons

• there are two notable exceptions to electronic configuration
• chromium
• 1s2 2s2 2p6 3s2 3p6 4s1 3d5
• copper
• 1s2 2s2 2p6 3s2 3p6 4s1 3d10

WHEW! That was a whole lot of information! Here is a worksheet with answers to test your knowledge!

http://misterguch.brinkster.net/PRA014.pdf

Atomic Structure

The atom is made up by three sub-atomic particles Electrons, Protons and Neutrons.



Protons are particles located in the atomic nucleus. They each have a positive charge. The number of protons of each element is equal to the atomic number

Electrons are tiny negative particles that are found around the nucleus. The number of electrons in a neutral atom is equal to the atomic number.

Neutrons are particles with a similar mass as protons also found in the nucleus. They have a neutral charge. The number of neutrons can be found by subtracting the atomic number from the atomic mass.

Isotopes
The atomic mass on the periodic table is actually an average of the actual atomic masses. This means the different variations of each element exists. For instance there are O-15, O-16 and O-17, however O-16 is the most common therefore we use O-16 as the average.

Atomic Theory

Throughout the decades many, many discoveries have been made by various individuals. Some ideas have grown from the help of newer generations of thinkers. ATOMIC THEORY is one of the concepts that, throughout the years has grown alot.

Greek philosophers suggested that matter was made up of atomos.

http://www.youtube.com/watch?v=ZnKqiojoFJU
- In 400 BC, Democritus was the first to propose that atoms were invisible particles.
-The came Aristotle, he proposed that matter was made up of earth, air, water, fire. He didnt not agree with Democritus's proposal. But his idea like Democritus wasnt proven because it was conceptual.
-Lavoisier stated the Law of Conservation of Mass and the Law of Definite Proportions. These laws suggested that in a compound of say, H2O, there will always be 11% Hydrogen and 89% Oxygen
-Joseph Proust experimentally proved Lavoisier's laws, and added that when a compound is broken down, products will exist in the same ratio as in the compound
-Then, in the early 1800s, John Dalton developed the basis of the modern Atomic Theory. He suggested that:

1. Elements were made of tiny indestructible spheres called atoms.
2. All atoms of an element were the same.
3. Atoms of a given element can be differentiated from another element by its relative atomic weights.
4. Atoms of one element will combine with atoms of other elements to create compounds.
-In the 1850's J.J Thompson created an experiment called the Raisin Bun Model. This model consisted of both positive and negative charges in a sphere like shape. With this he proposed that electrons existed.
-Ernest Rutherford explained why electrons spun around the nucleus, but he could not explain why the electron did not fall into the nucleus and destroy the atom.
-Thanks to Niels Bohr found a solution. Bohr was studying gaseous samples of atoms at the time, and came to the conclusion that electrons surrounding the nucleus were in specific energy levels. When the electron was excited, it would jump to a higher level. When an electron came back down, it would release energy in the form of light. Each of these jumps gives off light in different wavelengths; therefore creating different colours, as the colours ROYGBIV all have different wavelength
-an atom nowadays is considered the smallest particle of an element and cannot be broken down.
It contains 3 subatomic particles- the proton(+), the electron(-) and the neutron (0).
The protons and the neutrons occupy the nucleus and electrons exist in levels around the nucleus.

AND THATS A WRAP :)

enjoy this video....
http://www.youtube.com/watch?v=6p5nEhDv-cE&feature=related

Percent Yield and Percent Purity

So today we learned the awesome wonders of the "percent," i had no idea that we could relate percentage to chemistry! Just keep making our lives hard O CHEMISTRY GODS! Anywho I must get this done! So here we go.......



Percent Yield!
-the percent yield is calculated because sometimes not all of the reactants are used up, nor is it possible to recover all of the product.

%yield : (grams of product recovered /grams of product expected from stoichiometry) X 100

Heres an example video on how to calculate percent yield
http://www.youtube.com/watch?v=TKNxdL7DN1I

Example:

Given that the chemical formula for salicylic acid is C₇H₆O₃ and the chemical formula for aspirin is C₉H₈O₄.
In an experiment, 100.0 grams of salicylic acid gave 121.2 grams of aspirin. What was the percent yield?

Solution:

Step 1: Calculate the M_r (relative molecular mass) of the substances.

A_r : C = 12, H = 1, O = 16
So, M_r : salicylic acid = 138, aspirin = 180.

Step 2: Change the grams to moles for salicylic acid

138 g of salicylic acid = 1 mole
So, 100 g = 100 ÷ 138 mole = 0.725 moles

Step 3: Work out the calculated mass of the aspirin.

1 mole of salicylic acid gives 1 mole of aspirin
So, 0.725 moles gives 0.725 moles of aspirin
0.725 moles of aspirin = 0.725 × 180 g = 130.5 g
So, the calculated mass of the reaction is 130.5 g

Step 4: Calculate the percent yield.

The actual mass obtained is 121.2 g
So, the percent yield = 121.2 ÷ 130.5 × 100% = 92.9%

Percent Purity!
-reactants that are used in the equations and or experiments arent always pure, so thats why you must calcute the amount of pure substance

%purity:  (mass of pure substance/mass of impure substance) X 100

Example:

Chalk is almost pure calcium carbonate. We can work out its purity by measuring how much carbon dioxide is given off. 10 g of chalk was reacted with an excess of dilute hydrochloric acid. 2.128 liters of carbon dioxide gas was collected at standard temperature and pressure (STP).
The equation for the reaction is
CaCO₃ (s) + 2HCl (aq) → CaCl₂ (aq) + H₂O (l) + CO₂ (g)

Solution:

Step 1: Calculate the M_r of calcium carbonate

A_r: Ca = 40, C = 12, O = 16)
M_r of CaCO₃ = 100

Step 2: Calculate the grams from the volume

1 mole of CaCO₃ gives 1 mole of CO₂
1 mole of gas has a volume of 22.4 liters at STP.
22.4 liters of gas of gas is produced by 100 g of calcium carbonate
and 2.128 liters is produced by 2.128 ÷ 22.4 × 100 = 9.5 g

Step 3: Calculate the percent purity

There is 9.5 g of calcium carbonate in the 10 g of chalk.
Percent purity = 9.5 ÷ 10 × 100% = 95%

 Heres a link, it contains numerous practise sheets! enjoy
http://misterguch.brinkster.net/pra_equationworksheets.html