Atomic+Structure

Every thing is made up of atoms. Atoms consist of smaller particles called protons, neutrons and electrons. The properties of these particles is summarized below:
 * ~ Particle ||~ PROTON ||~ NEUTRON ||~ ELECTRON ||
 * Relative mass || 1 || 1 || 5 x 10-4 ||
 * Relative electrical charge || +1 || 0 || -1 ||
 * Where is it found || In the nucleus || In the nucleus || <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">In shells around the nucleus ||



<span style="font-family: Tahoma,sans-serif; font-size: 14pt;"> Atomic number (Z) is the number of protons is the nucleus of the atom. In the case of helium, shown above the atomic number is the sum of the red circles, that is 2. <span style="font-family: Tahoma,sans-serif; font-size: 14pt;"> Mass number (A) is the number of protons and neutrons in the nucleus of an atom. In the case of helium, shown above, the mass number is the sum of the red and the green circles, that is 4. <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Generally an atom is shown as follows:



<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">The mass number is shown on top (as a superscript) while the atomic number is shown below (as a subscript). <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">An example is Aluminium:



<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">The number of neutrons can be found by deducting the atomic number form the mass number (A-Z) <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">In case of aluminium that is 27-13=14 neutrons

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Isotopes are atoms of the same element that have the same atomic numbers but different mass numbers ( or different number of neutrons). <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Isotopes differ in the number of neutrons that they contain. //<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">For example: // <span style="font-family: Tahoma,sans-serif; font-size: 14pt;"> 6 Li 7 Li 8 Li <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">
 * <span style="color: #1ebb16; font-family: Tahoma,sans-serif; font-size: 16pt;">Isotopes: **

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Each of <span style="font-family: Tahoma,sans-serif; font-size: 14pt; vertical-align: super;">6 <span style="font-family: Tahoma,sans-serif; font-size: 19px;">Li, <span style="font-family: Tahoma,sans-serif; font-size: 14pt;"> 7 Li <span style="font-family: Tahoma,sans-serif; font-size: 19px;">and <span style="font-family: Tahoma,sans-serif; font-size: 14pt; vertical-align: super;">8 <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Li have 3, 4 and 5 neutrons in their nucleus, respectively.

//<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">"Isotopes have similar chemical properties as the they have the same number of valence electrons. However, they can have slightly different physical properties due to the difference in their mass number." //

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Usually an atom is neutral. This is because the positive charge of the protons is balance by the negative charge of the electrons, and the number of protons and neutrons is equal in a neutral atom.
 * <span style="color: #5343ef; font-family: Tahoma,sans-serif; font-size: 16pt;">Ions **

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">//When an atom gains an electron ,// it becomes negatively charged (forms an anion ) <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">//When an atom loses an electron ,// it becomes positively charged (forms a cation) <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">//Question:// find the number of each of the subatomic particles in the atom below? <span style="font-family: Tahoma,sans-serif; font-size: 14pt;"> 31 15 P 3- <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Protons = 15 <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Neutrons = 31-15= 16 <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Electrons = 18 (as the ion has a -3 charge, which implies that there are 3 extra electrons)

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Isotopes of some elements have so many neutrons that they become radioactive. That means that they emit waves of energy. <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Examples of uses of radioisotopes ( a radioactive isotope):

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;"> 14 C is used in carbon dating in order to measure the age of very old items. <span style="font-family: Tahoma,sans-serif; font-size: 14pt;"> 60 Co, another radio isotopes, is used in medicine in killing cancer cells.

<span style="color: #152fd5; font-family: Tahoma,sans-serif; font-size: 90%;"> By the end of this lesson you should be able to:


 * State the relative masses and charges of protons, neutrons and electrons
 * Define the terms mass number, atomic number and isotope
 * Deduce the symbol for an atom
 * Calculate the number of protons, neutrons and electrons from the mass number and atomic number

media type="facebooklike" key="http%3A%2F%2Fibchem4u.wikispaces.com%2FAtomic%20Structure" width="360" height="64"