Bonding

Question 1

What does ionic bonding occur between?

Answer 1

Metals and non-metals

Question 2

Describe the movement of electrons in ionic bonding:

Answer 2

Electrons are transferred from metal atoms to non-metal atoms

Question 3

What is ionic bonding a result of?

Answer 3

An electrostatic attraction between oppositely charged ions. This attraction extends throughout the compound

Question 4

What structure do ionic compounds always exist as?

Answer 4

Ionic lattices

Question 5

Why are ionic compounds always solids at room temperature and why do they have high melting points?

Answer 5

They are always solid at room temperature. They have giant structures and therefore high melting temperatures.
This is because in order to melt an ionic compound, energy must be supplied to break up the lattice of ions.

Question 6

Describe the conductivity of ionic compounds:

Answer 6

Ionic compounds conduct electricity when molten or dissolved in water. This is because the ions that carry the current are free to move in the liquid state but not the solid state

Question 7

Why are ionic compounds brittle and easily shattered?

Answer 7

Because they form a lattice of alternating positive and negative ions. A blow may move the ions and produce contact between ions with like charges

Question 8

What does a covalent bond form between?

Answer 8

A pair of non-metal atoms

Question 9

What is a covalent bond?

Answer 9

A covalent bond is a shared pair of electrons

Question 10

What is a small group of covalently bonded atoms called?

Answer 10

A molecule

Question 11

How does sharing electrons hold atoms together?

Answer 11

Atoms with covalent bonds are held together by electrostatic attraction between the nuclei and the shared electrons. This takes place within the molecule

Question 12

In a double bond, how many electrons are shared?

Answer 12

4

Question 13

Why do substances composed of molecules have low melting temperatures?

Answer 13

Because the strong covalent bonds are only between the atoms within the molecule. There is only weak attraction between the molecules so the molecules do not need much energy to move apart from each other

Question 14

Why are covalently bonded molecules poor electrical conductors?

Answer 14

Because the molecules are neutral overall. This means that there are no charged particles to carry the current

Question 15

What is a coordinate/ dative covalent bond?

Answer 15

A bond where one atom provides both of the electrons

Question 16

How do coordinate bonds compare with covalent bonds?

Answer 16

They have exactly the same length and strength as ordinary covalent bonds between the same pair of atoms

Question 17

What is a simple picture of metallic bonding?

Answer 17

Metals consist of a lattice of positive ions existing in a ‘sea’ of outer electrons which are delocalised (they’re not tied to a particular atom)

Question 18

What does the number of delocalised electrons depend on?

Answer 18

How many electrons have been lost by each metal atom

Question 19

Why do metals have giant structures?

Answer 19

Because the metallic bonding spreads throughout

Question 20

Why are metals good conductors of electricity?

Answer 20

Because the delocalised electrons can move throughout the metal structure

Question 21

Why are metals good conductors of heat?

Answer 21

Because of the sea of delocalised electrons as well as energy being spread by increasingly vigorous vibrations of the closely packed ions

Question 22

What does the strength of the metallic bond depend on?

Answer 22

• 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
• the size of the ion - the smaller the ion, the closer the electrons are the positive nucleus and the stronger the bond

Question 23

Why are metals generally strong?

Answer 23

Because the delocalised electrons extend throughout the solid so there are no individual bonds to break

Question 24

Why are metals malleable and ductile?

Answer 24

Because after a small distortion, each metal ion is still in exactly the same environment as before so the new shape is retained

Question 25

Why do metals have high melting and boiling points?

Answer 25

Because they have giant structures. There is a strong attraction between metal ions and the delocalised sea of electrons. This makes the atoms difficult to separate

Question 26

What is electronegativity?

Answer 26

Electronegativity is the power of an atom to attract the electron density in a covalent bond towards itself

Question 27

What scale is used to measure electronegativity?

Answer 27

The Pauling scale

Question 28

Why do the noble gases not have an electronegative value?

Answer 28

Because, in general, they do not form covalent bonds

Question 29

What three things does electronegativity depend on?

Answer 29

1. ) the nuclear charge
2. ) the distance between the nucleus and the outer shell electrons
3. ) the shielding of the nuclear charge by electrons in inner shells

Question 30

What is the trend in electronegativity up a group?

Answer 30

Electronegativity increases (the atoms get smaller) and there is less shielding by electrons in inner shells

Question 31

What is the trend in electronegativity across a period?

Answer 31

Electronegativity increases across a period because nuclear charge increases, the number of inner main levels remain the same and the atoms become smaller

Question 32

What is polarity?

Answer 32

It is about the unequal sharing of the electrons between atoms that are bonded together covalently. It is a property of the bond

Question 33

Why are electrons in covalent bonds between two atoms that are the same shared out equally?

Answer 33

Because both atoms have exactly the same electronegativity and the bond is completely non-polar

Question 34

What are polar covalent bonds?

Answer 34

Covalent bonds where one end of the bond is more negative than the other because of an unequal distribution of electrons

Question 35

Where do van der Waals forces occur?

Answer 35

They act between all atoms and molecules

Question 36

What is the strongest type of intermolecular force?

Answer 36

Hydrogen bonding

Question 37

What is a dipole moment?

Answer 37

The effect of the polarity of all the bonds in the molecule