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Recap of The Octet Rule PowerPoint PPT Presentation


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Recap of The Octet Rule. Atoms tend to gain, lose, or share electrons until they have eight valence electrons. Hydrogen is an exception. It shares only one electron to reach an outer shell of two electrons.

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Recap of The Octet Rule

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Recap of The Octet Rule

Atoms tend to gain, lose, or share electrons until they have eight valence electrons.

Hydrogen is an exception. It shares only one electron to reach an outer shell of two electrons

This helpful picture will act as a visual way to remember this – in the exam this will help. 


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Left to their own devices, atoms are electrically neutral.

That means that they have an equal number of

protons and electrons.

During the course of most natural events,

protons are not gained or lost, but electrons may be.

Atoms with more or fewer electrons than protons are

electrically charged. They are called ions:

an atom that loses electrons takes on a positive charge (cation);

an atom that gains electrons takes on a negative charge (anion).

Charged Atoms: Ions


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Ionic Bonds

  • What is an Ionic Bond?

  • An Ionic Bond is a chemical bond resulting from the TRANSFER of electrons

  • When is an ionic bond formed?

An ionic bond is formed usually when an electron is transferred from a metal to a non-metal and is the attraction between a +ve ion and –ve ion


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  • The transfer of the electron caused:

  • The previously neutral sodium atom to become a positively charged ion (a cation).

  • This is because the sodium now has one more proton than electron. Since protons have a +ve charge it is positive – it makes sense!!!!!

  • The previously neutral chlorine atom to become a negatively charged ion (an anion). 

  • This is because the chlorine has one more electron – since an electron is -ve charge…..

  • *An ionic bond is the resulting attraction for an anion and a cation after an electron is transferred from the metal to the non-metal.*

  • The attraction for the cation and the anion is called the ionic bond.

Sodium gives up an electron to chlorine.

This makes chlorine very happy, as it now has eight valence electrons. 

However – Sodium was being sneaky because he needed to get rid of that electron. Sodium is very happy, as it also now has eight valence electrons. 

The animation above the process that takes place during the formation of an ionic bond. The individual atoms are sodium and chlorine with only their valence electrons shown. Note that chlorine has seven valence electrons (it wants a full shell of eight), and that sodium has one valence electron (it also wants a full shell of eight).


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VISUAL LEARNING DEVICE

 Ionic Bonds: One big greedy thief dog!

Ionic bonding can be best imagined as one big greedy dog steeling the other dog's bone.  If the bone represents the electron that is up for grabs, then when the big dog gains an electron he becomes negatively charged and the little dog who lost the electron becomes positively charged.  The two ions (that's where the name ionic comes from) are attracted very strongly to each other as a result of the opposite charges.

EDDIE

Mr . Hall would be very proud of that


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®

· ·

[

]

Na

Na+

Cl

·

· ·

· ·

· ·

· ·

Cl

· ·

·

· ·

Ionic Compounds

A metal and a nonmetal transfer electrons to form an ionic compound.

  • Formation of sodium chloride:

+


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Atoms satisfy themselves by the give and take of outer shell electrons.

Most minerals are held together by primarily ionic bonds.


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INCASE : The ionic bond NaCl may not have sunk in yet so here it is againn.

WE LOVE NaCL


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NaCl:

Ionic Compounds

Ionic compounds consist of a lattice of positive and negative ions.


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What are some characteristics of an ionic bond?

  • Crystalline at room temperatures

  • Have higher melting points and boiling points compared to covalent compounds

  • Conduct electrical current in molten or solution state but not in the solid state

  • Polar bonds


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  • Atoms may form multiple covalent bonds - ie, share not just one pair of electrons, but two or more pairs. Atoms of different elements will form either one, two, three or four covalent bonds with other atoms.

Cl

Cl

Cl

Cl

Covalent Bonding

  • Covalent bonding is the term to describe bonding between non-metal atoms.

  • The atoms join to achieve a full outer electron shell and become ‘like the nearest noble gas’

    The OCTET Rule

  • Non-metals satisfy the octet rule by sharing electron pairs.

  • They CO-operate with each other- COvalent bonding.

  • By bonding, they become stable

    An easy example is Chlorine, Cl2

Chlorine atoms (unstable)

Chlorine molecules (stable)

elephant


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  • Covalent bonds are strong and a lot of energy is needed to break them. Substances with covalent bonds often form molecules, such as hydrogen and water, with low melting and boiling points.

  • Straight lines are the most common way to represent covalent bonds, with each line representing a shared pair of electrons.

  • A molecule of of oxygen (O2) consists of two oxygen atoms held together by a double bond, like this

  • A molecule of nitrogen (N2) has two nitrogen atoms held together by a triple bond, like this

Ethene, C2H4

  • 2 electron pairs are shared between the Carbons.

  • 1 electron pair between each hydrogen and carbon.


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