Structure and Bonding

Atom and Molecule| Structure of Atom| Ions| Bonding| Orbitals| Avogadro's constant|
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Atom and Molecule

Atom is the smallest part of an element which can exist as a stable entity.
Molecule is a group of atoms, and this is the form that substances exist.
For examples, an element hydrogen dose not exist as "H" alone. It exist as "H2". Water exist as "H2O" (two hydrogen atoms and one oxygen atom bonded together).

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Structure of atoms

Three fundamental particles are electron, proton and neutron. Electrons surround the nucleus of the atom. The nucleus, which contains protons and neutrons. Their relative mass and charges are listed below

Structure of an atom

Relative mass and charge
Particle Relative mass Relative charge
electron 0 -1
proton 1 +1
neutron 1 0

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Ions

Ions are atom or group of atoms with an electric charge. They can be either positive or negative. Positive ions are called "Cation" and negative ions are called "Anion".
An easy way to remember these two ions

"Cations are pussytive"

Pussytive cation

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Bondings

There are four types of bondings you have to remember Metalic Bonding occurs in metals (eg Mg, Cu). It can be described as "islands of cations in a sea of electrons".
islands of cations in a sea of electrons

Ionic Bonding is a complete transfer of electrons between atoms. For Example Na + Cl ® Na+ Cl-
ioninc bonding

Covalent Bonding is a force generated by sharing of electrons. Giant covalent bonding occurs in carbon compounds such as diamond and graphite. Generally, when covalent bonding is mentioned, it refers to simple covalent bonding.
covalent bonding

Hydrogen Bonding and Vander Waals forces are intermolecular forces which occurs between molecules.

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Orbitals.....shells and subshells

The term "orbital" is sometimes called "shell". Each shell can contain a certain number of electrons.

Each shell contains subshells. These subshells are designated by letter s, p, d and f. Each subshell has different energy, shape and orientation.

Therefore subshells contained in each shell will be

Now how do we know in what order the subshell are filled with electrons. The answer is, a small table show below can solve this problem.
Table for Subshells The red arrows show the order that electron is filled.

So the order will be: 1s 2s 2p 3s 3p 4s 3d 4p (4s fills electron before 3d)

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Amount of substances.....Avogadro's constant

Avogadro's constant (6.02x1024) is the number of molecules in 1 mole of a substance.
Now the question is how much is a mole??? This can be calculated from relative atomic mass shown in the periodic table.
For example, let's say you have 23g of Na (Sodium). If you look up the periodic table, it says 23 under Na, which means you have a mole of Na.
How about if you only have 12g of Na??? Well you can simply use the equation
Mole equation for atom So the answer will be 12 / 23 = 0.523
Therefore 12g of Na is 0.523 mole

Now you will probably think "how about molecules like H2O and O2??" Well the answer is easy.
Just substitute the "relative atomic mass" bit in the equation to "relative molecular mass".
Mole equation for molecule
What is relative molecular mass then? It is simply the sum of relative atomic mass.

So for H2O = 1+1 (two hydrogens) +16 (one oxygen) = 18
and for O2 = 16 +16 (two oxygens) = 32

Note: Relative atomic mass and relative molecular mass have NO UNITS!

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Contents & give your comment Structure and Bonding Inorganic Chemistry Organic Chemistry Physical Chemistry Calculation Techniques Definitions Periodic table References