march 24 Chem 11

BONDING
Covalent Bonding
- Electrons are shared between non-metals
- To draw Lewis Dot Diagrams:\

-Add the valence e- in all atoms
-Identify which atom can form the most number of bonds (this is shown by the pairs that only have 1 electron). This will be the central atom
-Bonds between two atoms are repesented by a line.
-All valence levels must be filled, all electrons must be used

- Some compounds form more than one bond between two elements, they will make double or triple bonds

Atoms V.S ions

- Atoms are electrically neutral
- # of protons = # of electrons
- Ions have a different number of protons and electrons
- Ions can either be positve (lose electrons) or negative (gain electrons)
- Cation = positive ion
- Anion = Negative ion
Here is a video about Atoms V.S Ions










Chemical Bonds - A bond is an electrostatic attraction between particles
- Bonds occur as elements try to achieve Noble gas electron configuration
- Noble gases (usually) do not form compounds or bonds
- In Noble gases the outermost energy levels have stable octets

Lewis Dot Structures - Atoms can be represented by dot diagrams - Dots represent electrons - Only valence electrons are shown - Write the atomic symbol for the atom - This represents the nucleus and filled inner energy levels - One dot is used to represent outer energy levles - One e- is placed in each orbital before any pairing occurs - Beginning with the 5th e-, pairing can occur up to a maximum of 8e- - Below: Electron dot diagrams for water

Ionic Bonds
- Electrons are transferred from metal to non-metal
- No dots are shown on metal
- "Charged" species are written in brackets

Here is a video about how to draw a dot diagram

March 26 chem 11

Electronegativity

- Atoms affinity for electrons
- Electronegativity increase from left to right and from bottom to top
- is is the tendency to attract electrons
-

Here is a video describing electronegativity

March 17 chem 11

Chemical Families and Relationships

The vertical columns in the periodic table are known as groups or chemical families. There are five groups: Alkali Metals, Alkaline Earth Metals, Transition Metals, Halogens and Noble Gases. Hydrogen is actually in a separate group on its own. Elements in the same chemical family have similar physical and chemical properties.

The Alkali Metals make up group 1 of the Periodic Table . Elements in this family are highly reactive and reactivity increases as you go down the group. These metals have only one electron in their outer shell and so,it makes them extremely electropositive. They react readily with non-metals such as oxygen and water, and usually have lower densities than other metals. They also are malleable, ductile, good conductors of heat and electricity and have low melting points. Finally, alkali metals are soft and can actually be cut with a knife.

Elements in the second column make uf the Alkali Earth Metals. They have two electrons in their outer shell and have low electronegativities. They are also less reactive than Alkali Metals but they will burn in air if heated. They will also react with water. They are all metals with a shiny, silvery white colour.

The Transition Metals are the 38 elements in groups 3-12 of the periodic table. They are very hard, have high melting and boiling points, low ionization energies, high electrical conductivity and are malleable, which means that they are able to be shaped and bent.

Halogens make group 17 of the periodic table. They are highly reactive non-metals. However they do not react well with water. Fluorine and chlorine are gases at room temperature, Bromine is a liquid and Iodine and Astatine are solids.

The last family is the Noble gasses, found in group 18 of the Periodic Table. The Noble Gases are the most stable and unreactive elements in the periodic table due to their full valence shells. They are colourless, odourless gases at room temperature. They also have high ionization energies and low boiling points.

Here is a long and boring (but educational) video of the periodic table

March 9 Chem 11

We got a group project assigned today. We are to provide a summary on one of the following topics:

Mendeleev's Periodic Table
Metals
Non-metals
Metalloids
Trends n Physical Properties of Elements on the Periodic Table
Trends in chemical properties of elements on the periodic table (ion charge, chemical reactivity,
ionization energy)
Properties of Alkalis, Alkaline Earth Metals, Halogens, Noble Gases and Transition Metals

The information is to be presented on a poster or powerpoint, and a summary and quiz must come with it

March 5th Chem 11

Friday, March 5, 2010

Today we learned about emission spectra...

-Each element gives off a specific colour of light
- These are known as emission spectra
- they are different to each element
-one of the uses for this is to find out what kind of elements a star is composed of
- If electrons absorb energy they can be bumped to a higher level
- When they fall to a lower level they release that energy as light

Heres a video about the emission spectrum of hydrogen






Atomic Structure

- Atoms are made up of parts called subatomic particles (protons, neutrons and electrons)

here are the details of each subatomic particle:

-A proton has 1 mass, +1 charge, and is in the nucleus
-A neutron has 1 mass, neutral charge, and is in the nucleus
-A electron is 1/1850 mass, -1 charge, and is arranged in energy level around the nucleus

Atomic Number

<------------ the number at the top left corner is the atomic number

- The nymber of protons determine the type of element
Isotopes

- Changing the number of neutrons changes the isotopes of the element
- All isotopes have the same chemical properties

For example carbon 12 has a 12 protons, and 6 neutrons
but as you add another neutron, the weight increases to 13 which gives you carbon 13
the same happens with carbon 14 respectively

Here is a little video about isotopes...

Mass number
-the total number of protons and neutrons

- Symbol given is A

- Different isotopes have different masses

Let's say you're given the Isotope of 12-Ca. The mass would be 12, the atomic number would stay the same as it is given in the periodic table (6), the number of protons would be 6 (same as the atomic number) and the number of neutrons would be 6 (mass number - atomic number).

here is a video about isotopes:

march 1st, Chem 11

today in class we learned about the ATOMIC THEORY
Early Atomic theory

Greeks history of early atomic theory
-In 300 BC, a man named Democritus said atoms were invisible particles, this was the first time the concept of atoms was mentioned

-The problem with this theory was that his theory could not be tested, and it was more of just a model explaining what atoms were thought to be

-Another problem was that there was no mention of the nucleus of any of its constituents

-a third problem was that it couldnt be used to explain chemical reactions, due to the exclusion of valence shell
-somehow, even with all of those problems, his theory was the most veiwed and accepted theory for over 2000 years

,

<------- basic atomic model of democritus

Lavosier (sometime in the late 1700s)

so later on we have the introduction of a man named Lavosier who introduced a few new things:

--Law of conservation of mass

--Law of definited proportions

- his theory was still not correct because it did not show what atoms were, or how they were arranged


Proust (1799)

now we have the indrocuction of proust some few years later, who more or less backed lavosiers laws and said:

-If a compound is broken down into its constituents, the products exist in the same ratio as in the compound (quote,unquote)

Dalton (early 1800s)

so now a few years later we have the introduction of a man lamed dalton, who introduced quite a few new things:

-he stated that atoms are solid, indestructable spheres, and how they relate the different elements

-a few problems were that he didnt mention isotopes, subatomic particles, or a nucleus

<------ the photo of a genious

J.J Thompson (1850)

so about 40-50 years later we get introduced to yet another scientist, J.J Thompson, who introduced quite a few new things

- He was the first man to introduce ( and is most well known for) his raisin bun model
- this basically stated that the nucleus was a solid positive sphere inside a *membrane* and that the atoms were negative particles embedded in the membrane
- he is the first man to introduce a theory involving positive and negative charges, and is also the first man to mention a nucleus
<-------------------------- raisin bun model

Rutherford (1905)

So something like 55 years later we get introduced to another scientist who worked, reworked and of course, introduced new ideas

- He showed that atoms have a dense center with electrons orbiting it (gold foil experiment)

- these results gave him a more planetary model of the atom, which explains why electrons spin around the nucleus

- He also suggests atoms are mostly empty space

- His problem with that method is that the atoms should attract the electrons, making every element extremely reactive
- He also didnt include valence electrons

<-------- Gold foil experiment














Bohr (1920)

15 years later we get introduced to the man that we refer to the most, and use his theory the most:

- He solved rutherfords problem by stating that electrons must exist in specific orbitals around the nucleus
-he also explained how valence electrons were used in atomic bonding
- he also explained the difference between ionic and covalent bonding
- he also includes the neutron