Chem Unit 1

Question 1

Element

Answer 1

A substrate that is made from only 1 type of element
92 natural elements

Question 2

Ion

Answer 2

An ion is an atom that has lost or gained one or more electrons
Metal ions are positive
Non are negative

Question 3

NO3

Answer 3

Nitrate

Question 4

OH-

Answer 4

Hydroxide

Question 5

CO3^2

Answer 5

Carbonate

Question 6

SO4^2-

Answer 6

Sulphate

Question 7

Ionic bonding

Answer 7

Giant structures
Arranges in lattice

Question 8

Cations are …

Answer 8

Positive ions
Metal ions lose electrons = positive ion

Question 9

Anions are …

Answer 9

Negative ions
Non metals gain electrons
Charge gained = 8 - group number

Question 10

Covalent bonding

Answer 10

Electrostatic attraction between a shared pair of electrons and nuclei of the bonded atoms

Question 11

Ammonia

Answer 11

consists of 3 hydrogen atoms bonded to a nitrogen atom. Each hydrogen atom has only 1 unpaired electron (1S’), so can form a single bond. The nitrogen atom has 3 unpaired electrons in its outer shell, so can form 3 bonds.

Question 12

Ammonium ions

Answer 12

forms from ammonia, NH3 and a hydrogen ion, H+. The hydrogen ion has no electrons in its vacant orbital to form a bond, but the nitrogen atom in ammonia has a lone pair not involved in bonding. It uses this pair to bond to the hydrogen ion, forming a dative covalent (coordinate) bond.

Question 13

Dative covalent

Answer 13

bond consisting of an electron pair derived from one of the atoms

Question 14

Strength of covalent bonds

Answer 14

Bond length and bond strength in = inversely related.
This means that the shorter the covalent bond length, the greater the covalent bond strength.

Question 15

What is metallic bonding?

Answer 15

Is a strong electrostatic attraction between positive metal ions and the delocalised electrons.
A giant lattice

Question 16

What are the physical properties of metallic bonding?

Answer 16

Electrical and thermal conductivity
High MP and BP
Malleable
Ductility

Question 17

Electrical and thermal conductivity

Answer 17

due to the delocalised electrons, which are free to move

Question 18

High MP and BP

Answer 18

due to strong electrostatic attractions between positive ions and electrons

Question 19

Malleable

Answer 19

can be shaped, as layers of positive ions slide over each other and the delocalised electrons move with the layers, so strong metallic bonds remain intact

Question 20

Ductility

Answer 20

can be pulled into wires as positive ions roll over each other and the delocalised electrons move with the positive ions, so strong metallic bonds remain intact.

Question 21

Electronegativity

Answer 21

The tendency of an atom to attract a bonding pair of electrons.

Question 22

The atoms share …

Answer 22

Electrons but they aren’t shared equally. The more electronegative an atom is the bigger one gets most share = polar molecule
Biggest = fluorine

Question 23

No difference in electronegativity

Answer 23

An equal share of electrons = pure covalent bond

Question 24

If there is a significant difference in electronegativity

Answer 24

The bigger it is the more share it gets = polar molecule
Has dipole end negative end and positive end

Question 25

Greater electronegativity than 2

Answer 25

Then it’s an ionic bond as only one atom gets electrons all the time

Question 26

Why does the MP decrease as the other goes down the group?

Answer 26

• Atoms are bigger as they have more shells
  -the distance between the nucleus and delocalised electrons are bigger
  -the force holding the structure together is weaker

Question 27

Group 1 v Group 2

Answer 27

• two delocalised electrons for each atom therefore a stronger bond
  -it has a positive charge = stronger MP
• the nuclei have more charge

Question 28

Intermolecular forces

Answer 28

Interactions between molecules caused by either permanent or induced dipoles

Question 29

Van Der Waals/ London forces

Answer 29

-Electrons are moving randomly within the shells of a molecule or atom.
-This can induce a temporary dipole in a nearby molecule. This results in a weak attraction.

Question 30

Dipole-dipole interactions

Answer 30

-Polar molecules such as HCl have permanent dipoles due to the much greater electronegativity of the chlorine atom and the fact that the molecule is not symmetrical.
-Hence the oppositely charged ends of two molecules are attracted to each other. This weak attractive force

Question 31

Hydrogen bonds

Answer 31

-This type of intermolecular force is the attraction between an electron-deficient hydrogen atom (o+) and O, N and F are the only atoms that can form hydrogen bonds as they are small and highly electronegative, which means they pull pairs of electrons towards them.