Atomic Structure

Subatomic Particles of an Atom:   Neutron, Proton, and Electron.

A neutral atom doesn't have any charges and the number of protons will equal the number the of electrons in the atom.

# of protons = # of electrons

The Atomic Number ( Z )

Also the same number of protons in an atom. Atoms do not have an overall charge. The atomic number is the same as the number of protons which are the same as the number of electrons.

Atomic number = # of protons = # of electrons

If a proton ( ¦ p ) is added to an element's nucleus,  a new element will be created.

For ex:   19 F + ¦ p ---> 20 Ne
               9                     10

Ions

Atoms have the ability to gain or lose electrons. Not many can do both, one such as hydrogen can though. They are able to do this by accepting electrons or giving them away to other atoms. Atoms that have done so are then called ions.

# of electons = protons - charge

Ions are electrically charged atoms.

• Negatively charged ion (anion) : when an electron is added to a neutral atom. non- metals tend to gain a positive charge and become neutral.
• Positively charged ion (cation) : when an electron is taken away from a neutral atom.

Mass Number, the total number of protons and neutrons

Because, atomic number = the number of protons, then :

• the atomic mass = the number of protons + the number of electrons
• the number of neutrons = the mass number - the atomic number

Atomic Mass

• the average mass of an element's isotope
• since most of the mass of an atom is concentrated in the protons and neutrons, the atomic is very close
• the mass number plus the atomic mass (weight) are not the same thing. atomic mass is the average of the naturally occurring isotopes, while the mass number is calculated by rounding the atomic mass to the nearest whole number instead of keeping decimal points
• if a neutron is added to an element's  nucleus, a heavier version of the same element (isotope) will be produced

For ex:   19 F + 1 n ---> 20 F
                9       0             9

Take a look at the following sites. Enjoy the song!

http://www.youtube.com/watch?v=lP57gEWcisY

http://www.youtube.com/watch?v=vUzTQWn-wfE&feature=related

-Lauren

Electronic Structure of the Atom

-         The Electronic Configuration of an atom =

o       A notation - describing the orbitals in which the electrons occupy

                                 - Describes the total number of electrons in each orbital.

               * This helps us understand the structure of the periodic table!

-         Bohr proposed- electrons exist in specific energy states

- when these electrons absorb or emit energy they moves from one orbital to another.

-         Energy level = amount of energy which an electron in an atom can possess

o       n is the number of the energy level

-         Quantum of energy = the energy difference between 2 particular energy levels

-         Ground State = when all electrons of an atom are in their lowest possible energy levels

-         Excited State= when one or more of an atom’s electrons are in energy levels other than the lowest available level

-         An Orbital = the actual region of space occupied by an electron in a particular energy level

-         Shell = the set of all orbitals having the same n value.

-         Subshell = a set of orbitals of the same type.

The letters s, p, d, f refer to 4 different types of orbitals

-         a maximum of 2 electrons can be placed in each orbit.

Order of orbitals

The order in which orbitals are filled is 1s, 2s, 2p, 3s, 3p…

Writing Electron Configuration for Neutral Atoms

o       always start at lowest energy level first

1)      Figure out how many electrons you have

2)      Start at lowest energy level (1s) and keep adding electrons until you have none left

Each electron has an opposite spin represented by:  ↑ and ↓

Example: Lithium is written 1s²2s²

Writing Electron Configuration for Ions

For a negative ion- add electrons to last unfilled subshell

For a positive ion- take away electrons (in the order you put them there)

Example: Sulphur 2-

        Sulphur has 16 electrons à Sulphur 2- has 18 electrons

            1s²2s²2p⁶3s²3p⁶

Core Notation

-         Core = the core of an atom is the set of electrons with the configuration of the nearest noble gas that comes before it.

-         Outer  = consist of all electrons outside the core. Core electrons normally take part in chemical reactions.

1)      Locate the atom à note the noble gas before the element

2)      Replace the part of the electron configuration corresponding to the configuration of the noble gas with the symbol for the noble gas in square brackets.

Example:

 

Youtube Time!!

http://www.youtube.com/watch?v=JNPFR-22MPA

-Candace