covalent bonds

- electrons shared between non-metals


to draw lewis dot diagrams:
- total all valence electrons in atoms
- identify the element that can form the most bonds. this will be the central atom
- draw bonds between atoms as a line (represents 2 electrons)
- any electrons not part of a bond are lone pairs around the atom
- check to make sure each atom has a full octet

example
ammonia water and ethane


C2H4


heres a extremely educational video!!

Atoms and Ions

• atoms are electrically neutral
• number of protons= number of electrons
• ions ahve different number of protons and electrons
• ions can be either positive of negative
• cation: positive ion
• anion: negative ion

Example: how many electrons do these electrons have? what type of ions are they?


S^2-: anion, sulphide ion I^1- : anion, iodide ion


chemical bonds

• a bond is an electrostatic attraction between particles
• bonds occur as elements try to acheieve noble gas electron configuration
• noble gases (usually) do not form compounds
• in noble gases the outermost energy level have stable octets
• metals lose electrons (oxidize)
• non metals gain electrons (reduced)

Lewis Dot Structure

• atoms can be represented by dot diagrams where dots represent electrons and only the valence level electrons are shown
• write the atomic symbol for the atom. this represents the nucleus and filled inner electron levels
• one dot is used to represent outer energy level electrons. one e- placed in each orbital before and pairing occurs. beginning with the 5th e-, pairing can occur up to a maximum of 8 e-

we practiced drawing lewis dot diagrams

Ionic Bonds

• electrons are transferred from metal to nonmetal. no dots are shown on the metal
• "charged" specie is written in brackets

so thats pretty much all we did today! lots of notes and lots of drawing :P

Atomic Weight

-On your periodic table silver has a weight of 107.9. The atomic mass of silver is 108. There is more than one isotope of silver and some are lighter than others.
a. 15.839% has a Mass Number of 107
b. 48.1161% has a Mass Number of 109
The element isn't split into half of the mass being 107 and 109 but it is intertwined together so it is difficult to separate. Uranium-238 is also difficult to separate.

To find the atomic weight for an element it is listed on your periodic table

24.305 would be the atomic mass for magnesium


54.938 would be the atomic weight for manganese

Emission Spectra, Atomic Structure and Isotopes

Emission Spectra

-Each element gives off a specific colour of light

-these are known as emission spectra(unique to each element)

-if electrons absorb energy they can be bumped to a higher level

-when they fall to a lower lever they release that energy as light

Atomic Structure

-atoms are made up of parts called subatomic particles

-protons(positive), electrons(negative), neutrons(neutral)

-atomic number = # of protons

Isotopes

-the # of protons determine the type of element

-changing the # of neutrons change teh isotope of the element

-all isotopes ahve the same chemical properties

Mass Number

-mass # is total of protons and neutrons

-symbol givven to mass is A

-different isotopes have different masses

-mass number = atomic # + # of neutrons(A=Z+N)

Bohr Model
- atoms are electrically neutral
-2 different models can be used to describe electron configuration : energy level model and bohr model
-electrons occupy shells which are divided into orbitals (orbitals always exist in pairs)
2e in 1st orbital, 8e in 2nd and 3rb orbital (octet)

EXAMPLES

Gold
bohr model:

energy level model:

6e-
2e-
8p+
O


aluminum
bohr model

energy level model:

3e-
8e-
2e-
13p+
Al


Orbital Shapes
atomic orbitals have a specific name and shape
1s / 2s look like this:

2px:


hybridized orbitals:
the 1st of the bohr levels is the 1st orbital and it holds 2e.
- the 2nd level contains 2s, 2px, 2py, 2p² orbitals. they hybridize to form one 2sp³


here is an extremely educational video that will enlighten 13 minutes of your life about orbitals:

Early Atomic Theory

Greeks

• in 300bc Democritus said atoms were invisible particles
• first mention of atoms (atomos)
• not a testable theory, only concept
• no mention of nucleus or sub atomic particles
• cannot explain chemical reactions
• this theory was the most accepted veiw for over 2000 years

Lavoisier (later 1700s)

• law of conservation of mass
• law of definite proportions
• wasn't a true atomic theory because it didnt discuss what atoms were or how they were arranged

Proust (1799)

• if a compound is broken down into its constituents, the products exist in the same ratio as the compound
• experimentally proved Lavoisier Laws

Dalton (early 1800s)

• atoms are solid, indestructable spheres (like billiard balls)
• provides for different elements
• no mention of subatomic particles
• cannot explain isotopes
• no mention of the nucleus

J.J. Thompson (1850s)

• raisin bun model
• solid positive spheres, with negative particles embedded in them
• first atomic theory to have positive and negative charges (protons and neutrons)
• introduces idea of nucleus
• no mention of neutrons so radioactive decay cannot be explained
• does not explain how electrons can exist outside nucleus
• does not explain neutrons role in chemical bonding

Rutherford (1950)

• showed that atoms have a positive centre with electrons outside it
• resulted in planetary models
• explains why electrons spin around the nucleus
• suggests atoms are mostly empty space
• should be unstable
• no mention of neutrons
• does not explain valence level electrons role in chemical bonds

i just had to put these guys in here cuz it is a prime example of how white kids can't rap and how i should never attempt it :P they mention dalton, thompson, rutherford and some other guy i dont know. ill explain Bohr after

Bohr (1920s)

• electrons must onlt exist in specific orbitals around nucleus
• explains how valence electrons are involved in bonding
• explains the difference between ionic and covalent bonding
• resolves the problem of atomic instability
• includes the neutron (discovered 1932)
• explains atomic emission spectra

oh look more white kids doing a terrible job of rapping! hahah at least they get his story across.

k so thats all we did today, a whole bunch of notes and learning about old folks who change chemistry as we know it!