Chemical bonding

Question 0

Why are ionic bonds so stable?

Answer 0

Because the reactant molecules have filled their valance shells in order to Create the bond so they are unreactive.

Question 1

What is an ionic bond?

Answer 1

This is when ions are created by transferring electrons until the valance shell is full.

Question 2

What holds the ions together in crystals?

Answer 2

Forces of electrostatic attraction between oppositely charged ions.

Question 3

What is lattice energy?

Answer 3

A measure of the strength of the electrostatic forces in an ionic crystal.

Question 4

What ions don’t have a noble gas structure?

Answer 4

The D block elements.

Question 5

What creates the forces of repulsion found in an ionic crystal?

Answer 5

The ions with the same charge

The forces between the inner shells of electrons and between positively charged nucleus

Question 6

What determines the distance between the atoms in a bond?

Answer 6

The balance of the repulsive and attractive forces.

Question 7

What is covalent bonding?

Answer 7

Covalent bonding exists between atoms when electrons are shared in pairs. In general the number of electrons involved is such to allow a noble gas structure to be built up around each atom.

Question 8

Describe the spin on the electrons involved in a single covalent bond.

Answer 8

They spin in opposite directions.

Question 9

Where do the attractive forces come from in a covalent bond?

Answer 9

That produced between the two positive nuclei and the negative charge cloud of the shared electron pair.

Question 10

Describe an electron density map for a covalent bond.

Answer 10

The bulk of it surrounds the two positive nuclei with only a little density in the internuclear region.

Question 11

Where do the repulsive forces come from in a covalent bond?

Answer 11

Between the inner shells of electrons in each atom.

Question 12

Describe an electron density map for an ionic compound.

Answer 12

The cloud is spherical around the nucleus of the ions with an area between the ions where there are no electrons.

Question 13

What is dative/co-ordinate bonding?

Answer 13

When both the electrons that form a covalent bond come originate from one of the atoms.

Question 14

How is a dative bond indicated in a structural formula?

Answer 14

It is drawn as an arrow which points to the atom receiving the two electrons.

Question 15

Give two examples of co-ordinate bonding.

Answer 15

Th reaction between ammonia and Boron-triflouride to produce NH₃BF₃

The production of ammonium from a hydrogen ion and ammonia.

Question 16

What do spectroscopic studies of the vaporised alkali halides show and what does this imply?

Answer 16

They show that the internuclear distance in these molecule is less than the in the corresponding ionic solid. Implying stronger bonding than in the crystal and this can only happen if there is a higher concentration of electrons between the nuclei, implying a distortion of the electron cloud of one or both ions from their usual spherical distribution.

Question 17

What does polarisation(distortion) of an ion represent?

Answer 17

The transition from ionic bonding to covalent bonding .

Question 18

What does the polarisation of the negative ion increase with?

Answer 18

With increasing ionic radius.

Question 19

What are the factors that might affect the distortion of the electron charge clouds around a negative ion?

Answer 19

A small cation is more effective than a large one as it can get closer to the anion.

The larger the charge on the cation, the more effective it is.

The larger the negative ion is, the more easily distorted it is as the electrons are further away from the nucleus so are attracted less strongly.

An anion with a larger charge will be more readily distorted as there is increased mutual repulsions between electrons and a greater quantity of negative charge to be transferred.

Question 20

Why aren’t the bonding electrons equally shared between atoms in a covalent bond?

Answer 20

Because the attraction of the nuclei or the bonding electrons will be different.

Question 21

Define electronegativity.

Answer 21

The ability of an atom to draw attract a pair of bonding electrons in a covalent bond to itself.

Question 22

Describe the trends of increasing electronegativity.

Answer 22

Electron negativity increases across a period and up a group.

Question 23

What are the electronegative elements in order of electronegativity?

Answer 23

Fluorine
Nitrogen
Oxygen
Chlorine.

Question 24

What is bond Polarisation?

Answer 24

It results from the unequal sharing of the bonding pair and represents the departure of the bond from pure covalancy and introduces some ionic character.

Question 25

What will bonds between elements of widely differing electronegativities result in?

Answer 25

They will be highly polar.

Question 26

What is the polarity of a covalent bond represented by?

Answer 26

δ⁺ And δ⁻ indicate the positions of the partial charges.

Question 27

Between what types of elements are covalent bonds formed?

Answer 27

Between two non-metals.

Question 28

What kind of structure do covalantly bonded atoms tend to have?

Answer 28

They have molecular formula (small or giant).

Question 29

Describe the melting and boiling points of covalantly bonded molecules.

Answer 29

They are small molecules and as such have low melting and boiling points.

Question 30

In What state do you tend to find covalent molecules at room temperature and pressure?

Answer 30

They are usually liquids or gasses.

Question 31

Do covalantly bonded compounds conduct electricity?

Answer 31

No.

Question 32

Between what types of elements are ionic bonds formed?

Answer 32

Between a metal and a non metal.

Question 33

What kind of structure do ionically bonded atoms tend to have?

Answer 33

Giant molecular structure.

Question 34

Describe the melting and boiling points of Ionically bonded molecules.

Answer 34

High melting and boiling points.

Question 35

In What state do you tend to find Ionic molecules at room temperature and pressure?

Answer 35

Usually solids.

Question 36

Do Ionically bonded compounds conduct electricity?

Answer 36

Yes, they conduct when molten or in solution.

Question 37

Describe the properties of metallic oxides.

Answer 37

They are basic in character. I.e if they are soluble in water they form alkalis.

They react with acids to produce salts and water.

Question 38

Describe the properties of non metallic oxides.

Answer 38

These are acidic in character I.e if soluble they form acids.

They react with alkalis to form salts and water.