Structure and bonding

  • Created by: amm242
  • Created on: 11-05-18 12:08
When does ionic bonding occur?
Between metals and non-metals
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What happens to electrons in ionic bonding?
They are transferred from metals to non-metals, forming positive and negative ions
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What is ionic bonding the result of?
Electrostatic attraction between oppositely charged ions
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Why do ionic compounds have high melting points?
Giant structures so lots of energy is needed to break up the lattice of ions. Strong electrostatic attraction between oppositely charged ions.
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When can ionic compounds conduct electricity?
When molten or dissolved in water because the ions are free to move
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Why do ionic compounds shatter easily?
Ions moving in a certain direction causes contact between like charges which repel
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What is a covalent bond?
A shared pair of electrons between a pair of non-metal atoms
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Why do simple molecular compounds have low melting points?
Strong covalent bonds are between the atom, but weak attraction is between molecules.
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How are covalent substances held together?
Electrostatic attraction between the nuclei and the shared electrons
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What is a dative covalent bond?
One atom provides both electrons in the shared pair
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How do dative covalent bonds occur?
Electron deficient atom accepts electron pair from atom donating lone pair
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Why are covalent substance poor conductors of electricity?
Molecules are neutral overall - no charged particles to carry current
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What is metallic bonding?
Giant structure - Lattice of positive ions in sea of delocalised outer electrons
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Why does the number of delocalised electrons vary between metals/
Depends on how many electrons can be lost by each metal atom
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Why are metals good conductors of electricity?
Delocalised electrons free to move through the structure
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Why are metals good conductors of heat?
Energy spread by vigorous vibrations of closely packed ions
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How does the charge on the ion affect strength of metallic bonding?
Greater charge, greater number of delocalised electrons, stronger electrostatic attraction between ion and electron
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How does the size of the ion affect strength of metallic bond?
Smaller ion, electrons closer to positive nucleus, stronger bond.
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Why are metals malleable/ductile?
Layers of positive ions can shift positions due to delocalised electrons
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Why do metals have high melting points?
Giant structure and strong attraction between +ve ions and electrons
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Define electronegativity
The power of an atom to attract the electron density in a covalent bond to itself
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How is electronegativity measured?
Pauling scale - higher no. = more electronegative
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What does electronegativity depend on?
Nuclear charge, sheilding, distance of electrons from nucleus
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Where are the most electronegative elements found?
Top right hand corner of periodic table
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What is polarity?
Unequal sharing of electrons between atoms in covalent bond
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When do dipole-dipole forces occur?
Between molecules that have permanent dipoles - polar overall
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What are van der Waals forces?
Force of attraction between all molecules/atoms caused by instantaneous dipoles
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When does hydrogen bonding occur?
Between hydrogen and very electronegative atoms with lone pairs (NOF)
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What happens to hydrogen atoms in hydrogen bonding?
Become electron deficient
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How is ice less dense than water?
Molecules held in fixed positions which are slightly less close
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Describe diamond
Carbon atoms form four covalent bonds, giant structure, strong covalent bonds
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Describe graphite
Carbons atoms form three covalent bonds, van der Waals between layers, delocalised electrons between layers
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Other cards in this set

Card 2

Front

What happens to electrons in ionic bonding?

Back

They are transferred from metals to non-metals, forming positive and negative ions

Card 3

Front

What is ionic bonding the result of?

Back

Preview of the front of card 3

Card 4

Front

Why do ionic compounds have high melting points?

Back

Preview of the front of card 4

Card 5

Front

When can ionic compounds conduct electricity?

Back

Preview of the front of card 5
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