3 Bonding

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  • Created by: Naana
  • Created on: 25-02-15 11:48
Where does ionic bonding occur?
Between metals and non-metals. Metals want to lose their outer electrons, whereas non metals want to gain electrons
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How are ions formed?
Electrons are transferred between metals atoms and non-metals atoms. Positive ions are formed when electrons are lost and negative ions are formed ions when electrons are gained
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Why does ionic bonding occur?
This is due to the electrostatic attraction between oppositely charged ions
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What are the properties of ionically bonded compounds?
Solid at room temperature. High melting temperature due to giant ionic lattice structure. Ionic compounds conduct electricity when molten or aqueous- ions that carry current free to move around
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Why are ionic compounds brittle (shatter easily when given sharp blow)?
This is because they form a lattice of alternating positive and negative ions. A blow in one direction will move ions so that they are in contact with ions of like charges
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What is a covalent bond and where does it form?
A shared pair of electrons. It forms between a shared pair of non metal atoms
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How does sharing electrons hold atoms together?
Atoms with covalent bonds are held together by the electrostatic attraction between the nuclei and the shared electrons
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What is a double covalent bond?
When atoms share two pairs of electrons (4 electrons)
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What is a molecule and why are molecules neutral?
A small group of covalently bonded atoms. They are neutral because no electrons have been transferred from one atom to another
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What are the properties of covalently bonded molecules?
Low melting points (not a lot of energy needed) - although strong covalent bonds between atoms there are weak intermolecular forces. Poor conductors of electricity- no charged particles
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What is coordinate bonding?
When one atom in the bond provides both the electrons. Atom that do donates has lone pair. Atom that accepts electrons is electron deficient
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What is a lone pair?
A pair of electrons in the outer shell of an atom that are not being used up in a bond
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What is electronegativity?
The ability of an atom in a covalent bond to attract electrons in a covalent bond towards itself
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What are the 3 most electronegative atoms?
Fluorine, oxygen and nitrogen
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Why does electronegativity increase as we go across a period?
The nuclear charge increases (number of protons increase) and atoms get smaller (atomic radius decreases) as electrons in the same shell are pulled in more closer to the nucleus
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Why does an atom electronegativity increase the smaller the atom is?
Because the smaller the atom, the closer the nucleus is to the shared outer main level electrons
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Why does electronegativity decrease as we go down a group?
The distance between the nucleus and the outer electrons increase and so the shielding of inner shell electrons increase
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What is polarity?
The unequal distribution of electron between atoms in a covalent bond. This produces a charge separation
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What is polar covalent bond?
When the electrons in the covalent bond are shared unequally between the atoms, as the atoms in the bond have different electronegativities
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What is a metallic bond?
The electrostatic force of attraction between positive metal ions and the delocalised electrons
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What does the number of delocalised electrons in a metallic bond depend on?
On how many electrons have been lost by each metal atom
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How does the strength of a metallic bond depend on the charge of the ion?
The greater the charge on the ion, the greater the number of delocalised electrons and the stronger the electrostatic attraction between the positive ions and the electrons
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How does the strength of the metallic bond depend on the size of the ion?
The smaller the ion, the closer the electrons are to the positive nucleus and the stronger the metallic bond
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What are the properties of metal?
Good conductors of electricity- delocalised electrons can carry a current and are free to move around. High melting points- strong electrostatic attraction between positive ion and electrons. Also giant structures so lot of energy needed
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What is dipole-dipole attraction?
An intermolecular force that results from the attraction between polar molecules (permanent dipoles)
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What are van der Waals forces?
The weakest intermolecular force that is caused by instantaneous dipoles and acts between all atoms and molecules
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What causes the size of the van der Waals forces to increase?
The more electrons there are in the molecule, the higher the chance that temporary dipoles will form. This makes the v.d.w's stronger between the molecules and so boiling points will be greater
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What causes instantaneous dipoles?
In any molecule the electrons are moving constantly and randomly. As this happens the electron density can fluctuate and parts of the molecule becomes more or less negative- a temporary dipole will form
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Where does hydrogen bonding occur?
It occurs in compounds that have a hydrogen atom attached to nitrogen, oxygen or fluorine which must have an available lone pair of electrons. Strongest intermolecular force
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Why do water, hydrogen fluoride and ammonia have higher boiling temperatures than might be expected?
Hydrogen bonding is present between the molecules (in addition to v.d.w's) and because hydrogen is a strong intermolecular force, the molecules are more difficult to separate
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What happens to hydrogen bonds when water is in its liquid state?
The hydrogen bonds break and reform easily as the molecules are moving about
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Why is water denser than ice?
The molecules are more closely packed
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What happens when water freezes?
The water molecules are no longer free to move about as the hydrogen bonds hold the molecule in fixed positions
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Other cards in this set

Card 2

Front

How are ions formed?

Back

Electrons are transferred between metals atoms and non-metals atoms. Positive ions are formed when electrons are lost and negative ions are formed ions when electrons are gained

Card 3

Front

Why does ionic bonding occur?

Back

Preview of the front of card 3

Card 4

Front

What are the properties of ionically bonded compounds?

Back

Preview of the front of card 4

Card 5

Front

Why are ionic compounds brittle (shatter easily when given sharp blow)?

Back

Preview of the front of card 5
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