Atomic Structure Again

Atomic Structure
Particle
Proton
Relative mass 1
Relative Charge +1

Neutron
Relative mass 1
Relative Charge 0

Electron
Relative mass 1/2000 or appro = 0 or 1/1840
Relative Charge -1

Proton number = Number of protons or neutrons in an atom
Nucleon number = sum of number of neutrons and protons in an atom. (Note this is not the same as relative atomic mass although in our syllabus it is the same for most atoms)
Isotopes are atoms of the same element having the same atomic number but different number of neutrons
Remember anything more than proton number 20, you CANNOT draw the electronic configuration. If the questions or number of valence electrons, LOOK AT GROUP NUMBER!!

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Json Lim
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Atomic Structure - The basics

Atomic structure is the study of how particles are arranged in an atom. To understand this, we need to know that atoms consist of 2 parts,
a)nucleus
b)electron shells.

The Nucleus
Simply put it, it is the part of the atom which you will find 2 kinds of particles, namely protons and neutrons.

Protons
Positively charged particle and it has a relative mass unit of 1.

Neutrons
Neutral and uncharged particle and it has a relative mass unit of 1.
Ok that basically sums up the particles found in the nucleus, lets go on to the electron shells.

Electron shells
Well as the name suggests, electrons are found here. Basically the electron shells are like holla hoops around a person and the electrons found in the electron shells spinning around the person at great speed. In an atom, the electron shells are found outside the nucleus and the electrons are spinning around the nucleus

Electrons
Negatively charged particles and have negligible mass compared to the other 2 particles.

A quick recap,

Subatomtic Particles Relative charge Relative mass Location
Proton +1 1 In the nucleus
Neutron 0 1 In the nucleus
Electrons -1 0 or 1/1840 Electron shells outside
nucleus

Cheers

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Entry by
Json Lim
http://www.oleveltuition.com/

Formulae of Ions Part 1 - First Twenty Elements

How do we find decide the ionic charges of the various ions? For O level examinations, you are expected to know how to derive the ionic charges for certain elements.

Technique.
Lets select an element, e.g. Magnesium.
Magnesium has the following information based on the periodic table.
Number of protons: 12
Number of neutrons: 12
Number of electrons: 12

The electronic configuration of magnesium is 2,8,2.
The next thing is to ask yourself, in order to obtain a stable electronic configuration (full outer electron shell), the atom needs to do something.
a) Lose 2 electrons so that the configuration becomes 2,8 (full outer electron shell)
b) Gain 6 electrons so that the configuration becomes 2,8,8 (full outer electron shell again)

From all the atoms' point of view, it is easier to lose 2 electrons than to gain 6. So in order to form a stable electronic configuration, magnesium will choose to lose 2 electrons and the updated sub atomic particles looks like this.
Number of protons: 12
Number of neutrons: 12
Number of electrons: 10
Since electrons are negatively charged and protons are positively charged, there will be a total of 12 positive charges and 10 negative charges and hence the overall charge is +2.
Therefore the charge on magnesium is +2

Lets take another example, oxygen.
Subatomic particles of oxygen atom looks like this
Number of protons: 8
Number of neutrons: 8
Number of electrons: 8
Electronic configuration: 2,6
In order to be stable oxygen needs to gain 2 electrons (instead of losing 6 electrons) to form a stable electronic configuration.

After gaining 2 electrons, the new numbner of subatomic particles looks like this.
Number of protons: 8
Number of neutrons: 8
Number of electrons: 10
In this ion, there are 8 positive charges and 10 negative charges, hence it has an overall charge of -2. Therefore the ion of oxygen has a charge of -2.

This is how you find the ionic charge of the first 20 elements. Cheers.

Enjoy!


Entry by
Json Lim
www.oleveltuition.com