Bonding
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Why are noble gases unreactive?
Full outer shell of electrons.
How do atoms form a full outer shell of electrons?
They bond together to share their electrons or transfer electrons.
What are the 3 types of strong chemical bonds?
Ionic Covalent Metallic
How do metals gain a full shell of outer electrons?
Lose electrnos
Where does ionic bonding occur?
Between metals and non-metals. Electrons are transferred from the metal to the non metal.
How are two oppositely charged ions attracted to each other?
Electrostatic forces of attraction
What is ionic bonding?
Electrostatic forces of attraction between oppositely charged ions.
What structure does ionic bonding exist as?
Giant ionic lattice
Describe the properties of ionic compounds.
Solids at room temperature Giant structures. High melting points (lot of energy required to break up the lattice of ions) Conduct electricity when molten or dissolved in water (the ions are free to move in the liquid state) Brittle and shatter easily.
Where does a covalent bond occur?
Between a pair of non-metal atoms. The atoms share some of their outer electrons. Covalent bond is a shared pair of electrons.
What are atoms with covalent bonds held together by?
The electrostatic attraction between the nuclei and shared electrons.
Describe the properties of covalent molecules.
Low melting points (the strong covalent bonds are only between the atoms within the molecules) Poor conductors of electricity (molecules are neutral there are no charged particles to carry a current)
What is co-ordinate bonding also known as?
Dative covalent bond
What are co-ordinate bonds represented by?
An arrow pointing towards the atom that is electron deficient.
What does the number of delocalised electrons in a metallic bond depend on?
How many electrons are lost by each metal atom.
Describe the properties of metals.
Good conductors of heat and electricity (delocalised electrons can move throughout the structure) Malleable (can be beaten into shape) Ductile (can be pulled into thin wires) High melting and boiling points (they have giant structures and strong attraction between metal ions and delocalised electrons)
Describe the strength of metals.
The strength of the metallic bond depends on: the charge on the ion - the greater the charge, the greater the number of delocalised electrons, the stronger the electrostatic forces of attraction. the size of the ion - the smaller the ion, the closer the electrons to the nucleus, the stronger the bond.
Define electronegativity.
The power of an atom to attract the electron density in a covalent bond towards itself.
What is used to measure electronegativity?
Pauling scale (0 to 4)
Why don’t noble gases have a value on the Pauling scale?
They don’t form covalent bonds
What does electronegativity depend on?
Nuclear charge Atomic radius Shielding The smaller the atom, the closer the nucleus to the outer electron, the greater the electronegativity. The larger the nuclear charge the greater the electronegativity.
Describe the trend in electronegativity down a group.
Decreases. Atom gets bigger down the group. More shielding by electrons in inner shells.
Describe the trend in electronegativity across a period.
Increases. Nuclear charge increases. Atoms become smaller.
What are the top 4 electronegative elements?
Fluorine>Oxygen>Nitrogen>Chlorine