27th April '09

[IONISATION ENERGY]: is the minimum energy required to remove one mole of electrons from one mole of gaseous atoms/ions to form one mole gaseous cations.

[FIRST IE]: The removal of one mole of electrons from one mole of gaseous atom to form one mole of singly-charged gaseous ion.

[SECOND IE]: The removal of one mole of electrons from one mole of singly-charged gaseous ion to form one mole of doubly-charged gaseous ion.

SUBATOMIC PARTICLES

- atoms are made up of protons, neutrons & electrons
- protons + neutrons = nucleons
& are found in dense (+)vely charged nucleus
- electrons are very light & are (-)vely charged

PROTON & NUCLEON NUMBER

* A= no. of protons + neutrons (no. of nucleons)
* Z= no. of electrons (atomic no./proton no.)
*A-Z= no. of neutrons

- Isotopes are atoms of the same element but with different number of neutrons
- Isotopes have the same chemical properties but different physical properties

- ISOELECTRONIC are atoms/ions that have the same no. of electrons

GROUND STATE: Atom has its electron in the lowest available energy level
EXCITED STATE: Electron absorbs energy to move to higher energy level

* When electron returns to a lower energy level, it gives out excess energy as LIGHT.

S, P, D, F ORBITALS

S ORBITALS: SPHERICAL SHAPED; NO DIRECTION
P ORBITALS: DUMB-BELL SHAPED; 3 DIRECTIONS (Px, Py, Pz)

in n^th shell, there are..
n subshells
(n)(n) orbitals
2(n)(n) of maximum electrons

SHELLS

when n=1,
No. of orbitals= 1
Max number of electrons= 2
S P D F
1 - - -

when n=2,
No. of orbitals= 4
Max number of electrons= 8
S P D F
1 3 - -

when n=3,
No. of orbitals= 9
Max number of electrons= 18
S P D F
1 3 5 -

when n=4,
No. of orbitals= 16
Max number of electrons= 32
S P D F
1 3 5 7

3 different laws when figuring the electronic configuration of an element

(1) Aufbac Principal
* the added electron always occupy the orbital with the lowest energy level

(2) Pauli Exclusion Principal
* each orbital can hold a max of 2 electron of opposite spin

(3) Hund's Rule of Multiplicity
* when filling a sub-shell, each orbital must be occupied singly before they are occupied in pairs

EXAMPLES OF S,P,D,F NOTATIONS:

i) F: 1s2 2s2, 2p5
ii) N: 1s2, 2s2, 2p3

NOBEL GAS CORE

iii) N: [He] 2s2, 2p3,
* Noble gas He represents 1s2 as there are 2 electrons in element Helium.

12 April '09

I AM BACK AFTER A LOOOOOONG HIATUS! :D

I've started Chemistry tuition and I've never felt this good. After a few weeks of bottling up, I poured out all of the questions which I need answers to and WAALA! I've got the answers. Tomorrow is the re-test on Mole Concept, hope I'd do better than my previous one. (:

An update on IONISATION ENERGY.

1st I.E. = X(g) ----> X+(g) + e-
2nd I.E. = X+(g) ----> X2+(g) + e-
ETC.

Definition of 1st I.E. > removal of one mole of electrons from one mole of gaseous atom to form one mole of singly-charged gaseous ion

Definition of 2nd I.E. > removal of one mole of electrons from one mole of singly-charged gaseous ion to form one mole of doubly-charged gaseous ion

THINGS TO NOTE:

1) the state symbol (g) is important! When talking abt I.E., everything must be present in the gas state.

2) I.E. measured in kJ/mol

22nd March '09

My field of interest would definitely lie in pharmacy.

Since I'm one of the few who cannot stand the look (or even the presence) of fresh blood and will get all dizzy at even the sound of it, I cannot become a doctor. Therefore, pharmaceutical science was my plan B.

As I aspire to help people and hopefully save lives (even though people said "DIAN, PEOPLE WILL DIE UNDER YOUR CARE BECAUSE YOU'RE SUCH A LAZY BUM"), I want to handle and hopefully create new drugs which can cure and reduce my patient's pain.

I checked my MI Link way past the NUS/NTU/NIE open houses and was a tad bit disappointed because I actually planned to go there and interview one of the aspiring doctors. Then, I tried to call my Chem/Phy tutor who tutored me last year for O Levels because he was undergoing a medicine course. However, he could not be reached (I think he changed number), so I decided to just research on the course! :)

RESPONSIBILITY:

* responsible for the registration of medicines & the continual review of approved medicinal products

* facilitate the timely introduction & availability of new and innovative quality medicines in Singapore and the region, including medicines targeted for diseases prevalent in the region

MAIN ACITIVITES RELATING TO THE CONTROL OF MEDICINAL PRODUCTS INCLUDE:

* evaluation and approval of applications for new product licences, amendment and renewal of existing product licences

* continual review of registered medicinal products

* evaluation and approval for import of unregistered medicinal products on a named patient basis.

* approval for the import of medicinal products for the purpose of re-export

* evaluation and approval of applications for licences for the purpose of importation of registered medicinal products on a per consignment basis

22nd March '09

People always say: "Put ahead all your weaknesses first, then feed yourself with your strengths."

(NOT SURE IF THAT WAS REALLY WHAT PEOPLE ALWAYS SAY OR NOT, BUT IT DOESN'T MATTER BECAUSE IT SOUNDS NICE!)

Weaknesses in Chemistry

1) I think I'm in deep shit because I still don't understand the combustion data. CxHy(g) + (x+y/4)O2(g) -> xCO2(g) + y/2H2O(l)

EVEN AFTER READING FOR A ZILLION TIMES, I STILL DON'T GET IT, THAT'S WHY I GOT STUCK IN A LOT OF QUESTIONS IN THE PREVIOUS ASSIGNMENTS. IT'S HOLDING ME UP AND CAUSING ME TO HAND IN MY ASSIGNMENTS LATE. SOS I NEED HELPPPPP!!!!

2) I get demoralised very quickly (even in any other subjects) when I don't get the topic that we're learning. And I'm quite weak in self-learning so the next chapter might be quite a hassle for me. Nevertheless, I'll try!

3) I procrastinate a lot. Last Friday, I actually had the intention to blog right after I reach home from hockey. But in the end, I decided to do something else. And now, I'm blogging a week's work in a day. I need treatment.

Strengths in Chemistry

1) I have always thought that my calculation was very good. Used to get full marks during sec sch and all but then as mentioned, I got stuck on the combustion data formula thingy and that holds me back!

2) I am ok when it comes to balancing equations but I think I take quite some time to balance it. I prefer not to rush. Rush = more mistakes!

3) My love and interest for science helps me stand strong and persevere. Although I prefer Physics more, I know that chemistry is also needed and is part of our daily lives. Therefore, I want to do good in both sectors :)

3rd March '09

1) Common Apparatus used in lab:

- deionised/distilled water
- white tile
- beaker
- pipette filler
- retort stand
- funnel
- pipettes
- conical flask
- burette
- dropper
- glass rod
- volumetric flask
- weighing bottle
- electronic analytical balance

2) To prepare standard solutions:

eg Using a fixed mass of solid sample
-requires weighing

OR

Using a fixed volume of liquid sample
- requires use of pipette

2) Choosing an appropriate weighing vessel.

a) Ensure the weighing pan is clean.
Use a brush to remove solid particles or a paper towel to wipe off liquids.
b) Tare the balance.
c) Centre the vessel on the balance.
d) Add the required mass of substance into the vessel.
e) Record the mass after the reading has stabilized.
f) Before leaving, ensure the balance pan is clean from spills.
g) Transfer sample to a container, and re-weigh the vessel.
h) Mass of sample transferred is the difference in of the two readings.
i) Recording readings to appropriate number of decimal places.

Tips & Precautions


Use a draft shield for accurate mass readings.
Use a clean and dry weighing vessel.
Use a weighing bottle for weighing hygroscopic substances.
Allow a hot sample to cool before weighing.
When weighing volatile substances, ensure you seal the vessel before taking the final mass reading.
Ensure the substance weighed is dry.

3) Choosing an indicator

a) BROMOTHYMOL BLUE; strong acid-strong base
b) PHENOLPHTHALEIN; weak acid-strong base
c) METHYL ORANGE; strong acid-weak base

4) When reading the liquid level...

Eye should be at level of meniscus, not above or below.
Reading from an angle results in parallax error.

2nd March '09

(1) Learnt that H3PO4 is actually Phosphoric acid.

(2) Was told to memorize the definition of important terms in chemistry.

eg, Relative isotopic mass is defined as the mass of one atom of an isotope* compared with 1/12 the mass of one atom of carbon-12.

* recapping chemistry o levels, isotopes are atoms with the same number of protons but different number of neutrons.

eg2, Relative atomic mass (Ar) is defined as the mass of one atom of an element compared with 1/12 the mass of one atom of carbon-12.


Things to learn:
How to type the small numbers of the formula via the keyboard. Forgot the steps Ms Jee taught us the other day. Anyone?

24th February '09

Binary Covalent Nomenclature Tutorial

1) Binary covalent compounds are pure substances that consist of two nonmetallic elements.

2) The water, H2O, you boil to cook your potatoes and the methane, CH4, in natural gas that can be burned to heat the water are examples of binary covalent compounds.

3) MEMORIZED NAMES:

water - H2O
ammonia - NH3
methane - CH4
ethane - C2H6
propane - C3H8

4) The general pattern of such formulas is AaBb, where “A” and “B” represent symbols for nonmetals.

eg. nitrogen and oxygen are nonmetallic elements, the formula N2O3 represents a binary covalent compound.

5) Follow these steps to write the names for binary covalent compounds.

If the subscript for the first element is greater than one, indicate the identity of the subscript using one of the prefixes listed below . We do not write mono- at the beginning of a compound’s name.
Example: We start the name for N2O3 with di-.

Attach the selected prefix to the name of the first element in the formula. If no prefix is to be used, begin with the name of the first element.
Example: We indicate the N2 portion of N2O3 with dinitrogen.
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Select a prefix to identify the subscript for the second element (even if its subscript is understood to be one). Leave the "a" off the end of the prefixes that end in "a" and the “o” off of mono‑ if they are placed in front of an element whose name begins with a vowel (oxygen or iodine).
Example: The name of N2O3 grows to dinitrogen tri-.

Write the root of the name of the second element in the formula as shown below.
Example: The name of N2O3 becomes dinitrogen triox-.

Add -ide to the end of the name.
Example: The name of N2O3 is dinitrogen trioxide.

6) Prefixes:

1 - mon(o)
2 - di
3 - tri
4 - tetr(a)
5 - pent(a)
6 - hex(a)
7 - hept(a)
8 - oct(a)
9 - non(a)
10 - dec(a)

Cation Names and Formulas

1) The names of monatomic cations always start with the name of the metal, sometimes followed by a Roman numeral to indicate the charge of the ion.

eg Cu+ is copper(I), and Cu2+ is copper(II).