Electronegativity and Polarity

 Hello, and today in class we have discussed Electronegativity.  Now what is this large word?

Electronegativity - A measure of the tendency of an atom to attract electrons from a neighbouring atom.

After reading this definition, you may be wondering, what does that mean???  Well, here is a chart to help you understand better of what it means.

According to this chart, electronegativity values are much more higher at the family of noble gases, and on the far left of the table, the electronegativity is the weakest.

The formula for determining how high the value is, is to use the equation: |value| = |energy1 - energy2|.  Notice the absolute value bars.  Those indicate that the value will always be positive.


Here are some rules to follow:

1. Non-Polar Covalent bonds are formed when the difference between the values is less than 0.5
2. Covalent bonds are formed when the difference is between 0.5 and 1.8
3. Ionic bonds are formed when the difference is over 1.8


Lets do an example:  Hydrogen and Fluorine.


Hydrogen's value is 2.2 and Fluorine's value is 3.98.


3.98-2.2 = 1.78.


These two are covalent bonds because when formed, the difference is between 0.5 and 1.8!

Here is a video, if you guys still do not understand.  Enjoy!

Periodic Table Trends

HELLO!  HOW YOU DOING!  Okay, so today we went to the lab and discovered different types of trends using Microsoft Excel.

BACKGROUND
In 1870, Dmitri Mendeleev first proposed a new of studying and organizing the then known 63 elements. The modern form of the table has been modified and improved many times since Mendeleev's tables.  Pioneers like Moseley(1913) and Seaborg(1941) have made the properties of the elements much simpler to study and understand.

So, the important trends to remember:

Electronic Structure - Electron configuration and Valance Electron.

Brief summary through definition and some new vocabulary:

•  Energy level: the amount of energy that electron can possess.

• Ground State: it is when all the electrons are in lowest energy level.
• Excited State: when electrons are in the energy level that different from the lowest level
• Orbital: is the region, like the milky way surrounding around the nucleus that electron occupies in particular energy level
• A shell: is the set of all the orbitals have same energy levels

• Sub-shell: is the set of orbital of the same types (s,p,d,f) 

• Electron Configuration: is the notation that describes the orbital in which electron occupies and the total number of electron each orbital

 

 Or this

Actually, i find the first chart easier to count and do exercise but its up to you. Here's how ->
Usually in test you will be given question like this: Given element Na, write the electron configuration. Don't freak out yet, follow these steps !

1. Look into your periodic table to find that element. In this case, we found Na located in Group IA, period 3
2. Then find the element's proton's number, usually in the top left in the box
3. We all known that if the element is not ion, the number of electron = number of proton
4. So we will be able to know how many electron are there in the element. Okay keep in mind that number.
5. then we follow the route on the periodic table from left to write, top to bottom
6. So finally we just follow that route till we reach that element
7. I can write without think of anything: 1s2 2s2 2p6 3s1

Oh snap i forgot to mention the core notation. Arr i hate chemistry name so much, the core notation is basically the short form of the electron configuration that is easier and faster to write. Its in the form of [X] s(x) p(y) ... Here are steps:

1. Follow steps 1 above
2. Look backward to the previous row, then find the noble gas ON THE BACK ON YOUR ELEMENT, NOT IN FRONT OF
3. Write that noble gas in bracket in this case [Ne]
4. Then continue to write the electron configuration till you reach your element. => [Ne] 3s1

 Here are some scientist contributed to this concept

1. The Pauli Exclusion Principle: in every given energy level, each orbit can only contains 2 electrons

1. The Niel Bohr Principle: electron exists in a specific energy states and can be filled up from low level to high level

1. Hund Rule: the Hund rule states that electron don't pair up unless they have to, that means they will fill out 1/2 the orbit first.

Valance Electron:

It's basically the number of electron in the outer most shell. Or orbital

Ex: The Valance Electron of Na ( [Ne] 3s1 ) is 1 cause there's only 1 electron in the outer most shell

A little history about the atom

DEMOCRITUS

• Stated that atoms were different in form, position and magnitude; all things were made of atoms, and atoms were small, full, unbreakable, pore-less and homogeneous.

ANTOINE LAVOISIER

• Proved the law of conservation of mass around 1789.

JOHN DALTON

• Formed the atomic theory: all matter is composed of tiny, indestructible particles.

JJ THOMSON

• discovered the election

ERNEST RUTHERFORD

• Atomic model made.
• Using gold foil experiment, discovered alpha and beta rays and presumed electrons were located outside nucleus.

ROBERT MILLIKAN

• Using falling-drop method, proved that the charge was a constant for all electrons therefore demonstrating atomic structure of electricity.

MARIE CURIE

• Studied radioactivity; concluded that the ability to radiate didn't depend on arrangement of the atoms in a molecule but that it has to be linked to the interior of the atom itself.

JAMES CHADWICK

• Proved the existence of neutrons: particles without electrical charge.
• The neutron has a similar mass to a proton.

MAX PLANCK

• Originator of quantum theory.
• Discovered that light was released in heat sources in a pattern of frequencies for different elements.

ALBERT EINSTEIN

• Established the law of mass, theory of relativity and using Planck's theory, formulated photon theory of light.

LOUIS DE BROGILE

• Believed electrons acted like particles and waves
• Waves produced by electrons contained in orbit had certain energy, frequency and wavelength

JOSEPH LOUIS PROUST

• Established law of definite composition and law of definite portions

ERWIN SCHRODINGER

• Combined equations for behaviour of waves with Brogile's equation of electrons in atom.

NIEHL'S BOHR

• Propsed Bohr model (modified Rutherford model)
• Proposed that electrons travel in certain successively larger orbits.
• Electrons jump from outer to inner orbit which emits light

To learn more about these AMAZING scientist... feel free to check out these sites!

http://hi.fi.tripod.com/timeline/

http://atomictimeline.net/index.php

Structure of the Atom

Structure of the Atom


Hello all, today we learnt about the structure of the atom woooohoooo.  Here is what we learned!

An atom contains 3 subatomic particles called:

protons
-Represented as 1
                          1 P

electrons
-Represented as 1
                          0 N

neutrons
-Represented as 0
                         -1 E

On the periodic table:

Atomic Number = # of protons = # of electrons
Atomic Mass(average) = # of protons + neutrons

Ions = # of electrons - charge

Anions = negatively charged ion

Cations = positively charged ion

What are isotopes?  Well they are:

-The same element, but heavier.