Topic 3 - Chemical Bonding Flashcards
What are ionic compounds?
Oppositely charged ions held together by electrostatic attractions.
Can ionic compounds conduct electricity?
Only in aqueous solution or when molten.
What are the melting points of ionic compounds like?
High.
Why do ionic compounds have high melting points?
Many, strong electrostatic forces between oppositely charged ions that need lots of energy to overcome.
Why do ionic compounds conduct electricity when molten?
The ions are free to move.
Why do ionic compounds conduct electricity when in aqueous solution?
Water molecules are polar and can attract the positive and negative ions and break the structure so the ions are free to move.
Why are ionic compounds brittle?
When struck, the layers slide and positive ions get next to positive ions and repel and break the structure.
What is a way to show evidence for charged particles?
Electrolysis of copper(II)chromate(VI) on wet filter paper.
What color is copper(II)chromate(VI)?
Green.
What happens when a drop of green copper(II)chromate(VI) is placed on wet filter paper and electricity is passed through it?
The ions start to separate.
What is the charge on a copper(II) ion?
2+
Where do the Cu2+ ions go?
They move toward the negative cathode.
What color is the Cu2+ solution?
Blue.
What is the charge on a chromate(VI) ion?
2-
Where do the CrO4^2- ions go?
The move towards the positive anode.
What color is the CrO4^2- solution?
Yellow.
What is covalent bonding?
The sharing of electrons in order for the atoms to obtain a full outer shell.
Where is the electrostatic attraction in a covalent bond?
Between the shared electrons and the positive nucleus.
How many types of covalent bonds are there, and what are they?
3
Single, double, and triple bonds.
What is a dative covalent bond?
Where one atom donates 2 electrons to an atom or ion to form a bond.
What is an alternate name for a dative covalent bond?
Coordinate bond.
How is a coordinate bond represented in a diagram?
An arrow.
What is bond enthalpy?
The strength of the bond.
What is the relationship between bond enthalpy and the length of the bond?
The shorter the bond the higher the bond enthalpy.
Why does a shorter bond length lead to higher bond enthalpy?
Greater electron density between atoms = stronger attractive force = atoms are pulled closer together = shorter bond length = higher bond enthalpy.
What causes bond length?
Attractive forces and repulsive forces.
What two things determine the shape of a molecule?
The number of bond pairs and lone pairs of electrons.
What is the bond angle in a tetrahedral molecule?
109.5*
What is the general rule for no. of lone pairs and bond angles?
For each lone pair added, reduce the bond angle by 2.5*.
What shape and bond angles will a molecule with 4 bond pairs and no lone pairs of electrons have?
Tetrahedral. 109.5*.
What is the shape and bond angles of a molecule with 2 bond pairs and no lone pairs of electrons?
Linear. 180*.
What shape and bond angles will a molecule with 3 bond pairs and no lone pairs of electrons have?
Trigonal Planar. 120*.
What shape and bond angles will a molecule with 5 bond pairs and no lone pairs of electrons have?
Trigonal Bipyramidal. 90* and 120*.
What shape and bond angles will a molecule with 6 bond pairs and no lone pairs of electrons have?
Octahedral. 90*.
What shape and bond angles will a molecule with 3 bond pairs and 1 lone pairs of electrons have?
Pyramidal. 107*.
What shape and bond angles will a molecule with 2 bond pairs and 2 lone pairs of electrons have?
Bent. 104.5*.
What shape and bond angles will a molecule with 3 bond pairs and 2 lone pairs of electrons have?
Trigonal Planar. 120*.
What shape and bond angles will a molecule with 4 bond pairs and 2 lone pairs of electrons have?
Square Planar. 90*.
What are two examples of giant covalent structures?
Graphite and diamond.
Why does graphite have a high melting point?
Lots of strong covalent bonds.
Why do graphite layers slide easily?
Weak forces between the layers.
Can graphite conduct electricity?
Yes
Why can graphite conduct electricity?
Delocalized electrons float between the layers and can carry a charge.
Why does graphite have a low density?
The layers are far apart in comparison to covalent bond length.
Is graphite soluble or insoluble?
Insoluble.
Why can diamond conduct heat well?
Tightly packed, rigid arrangement.
Why does diamond have a very high melting point?
Lots of strong covalent bonds.
Is diamond soluble or insoluble?
Insoluble.
Can diamond conduct electricity?
No
Why can’t diamond conduct electricity?
No delocalised electrons.
What other substance has a similar shape and properties to diamond?
Silicon(IV) dioxide.
What is a sigma bond?
When two orbitals overlap.
What are pi bonds?
The parallel overlap of 2 p orbitals.
What bonds does a double bond contain?
A sigma and a pi bond.
What is benzene?
A cyclic, planar molecule with the formula C6H6.
What is electronegativity?
The ability for an atom to attract electrons towards itself in a covalent bond.
Where are the most electronegative elements found in the periodic table?
Top righthand corner.
What is the most electronegative element in the periodic table?
Fluorine.
What is the Pauling Scale?
A scale that quantifies how electronegative something is with a higher number meaning more electronegativity.
