Science e-Portfolio Post 1

This is my 1st reflection of my Science e-Portfolio. Please enjoy!

Reflection of learning in Science and personal growth

This term for Science, we covered the following Chemistry Topics:

• Periodic Table
• Atomic Structure
• Chemical Bonding
• Equation Writing
• Isotopes
• Acids, bases and salts

I am glad that at the end of Term1, I have learnt the followings:

• Interpret the Periodic Table and predict the elements properties based on their position in the periodic table
• Represent the atomic structure and bonding via the dot and cross diagram
• Balancing of the chemical equation
• Understand the properties of Acids and Bases and how metals react with them

Topics	Issues in Learning Sciences & Reflection of Growth
Periodic Table	Elements are arranged in periodic table in order of their proton number. In each group, the number of outer shell electrons is the same for every element in that group and is equal to the group number. These electrons in the outer shell are used to form bonds between atoms. These electrons are called valence electrons. Thus, elements in the same group form the same type and number of bonds as they have the same number of valence electrons. Groups 1, 2 and 3 forms positive ions with 1+, 2+ and 3+ respectively, where as Group 5,6,7 forms negative ions with 1-,2- and 3- respectively. However I do not understand why transition metal has more than one type of ions, such as Fe(II) and Fe(III).
Atomic Structure	It is interesting to learn that from the 21st element onwards, they have different electronic configuration compared to the first 20 elements in the Periodic Table. For the first 20 elements, the first, second and third shell can hold maximum 2,8,8 electrons respectively. However for elements after the Calcium, the third shell can hold up to 18 electrons. I would like to understand why there is this difference. Initially, I was having difficulty understanding the charge of polyatomic ions such as OH, NO3 and SO4. However, this website http://library.thinkquest.org/C006669/data/Chem/bonding/lewis.html , has though me how to derive the charge.
Chemical Bonding	The two extreme chemical bondings are Ionic Bonding and Non-Polar covalent Bond. Ionic Bonding is resulted when electrons are transferred from an atom to another atom, forming negative ions (anions) and positive ions (cations), whereas Covalent bonding are results of atoms which are joined together by sharing of electrons to form molecules. Typically, Ionic bond exists between metal & non-metal atoms and Covalent bond exists between non-metals. However, Aluminum chloride and Beryllium chloride are polar covalent bond due to the small electronegativity differences which is not great enough to create an ionic bond.
Writing Equation	To balance the equation is actually not difficult; we just need to observe the principle that the number of atoms of reactants must be equal to the number of atoms of products. Balancing chemical equations literally means counting the number of times the atom symbols appear in the reactants and products to make sure the counts are the same on both sides. Conservation of mass is linked to "conservation" of element symbols. What I find more challenging is to derive the products of the reactants. For example, how one would know that when methane (CH4) reacts with Oxygen(O2) the products are Carbon Dioxide (CO2) and Water (H2O) and not Carbon, Oxygen and Hydrogen separately.
Isotopes	Isotopes are atoms of the same element with different numbers of neutrons. As they have the same number of protons and electrons, they will have the same chemical properties. However they do have some small differences in their physical properties, because of the difference in the number of neutrons the particular isotope has.
Acids, Bases (Alkali) and Salts	Is interesting to note that acids only behave as acids when they are dissolved in water. The properties of acid are due to presence of hydrogen ions H+ (aq). Similarly the properties of bases are due to presence of hydroxide ions. In order to write correct equation, one must remember the reaction of metals with acid vs. bases. Acid reacts with reactive metals to form salt and hydrogen gas. Acid reacts with Bases to produce salt and water. Acid reacts with Carbonates to produce Salt, Carbon Dioxide and Water

Thank you!