Section 2 - Periodic Table and Bonding

Question 1

The periodic table

Answer 1

• elements are in increasing atomic number
• vertical columns are called groups
• group number corresponds to the number of electrons that element has in its outer shell
  Group 1 - Alkaline Metals
  Group 7 - Halogens
  Group 0 - noble gases
• rows = periods, properties change drastically along them

Question 2

elements in a group

Answer 2

have the same number of electrons in the outer shell

The properties of elements depend on the number of electrons they have, therefore atomic number is very significant, but the most important thing is the number of electrons in the outer shell

Question 3

electron shell rules

Answer 3

• electrons always occupy shells with the lowest energy levels filled first
  2, 8, 8, 2 is the configuration of electrons allowed in each cell

Question 4

working out electronic configurations

Answer 4

use period and group
- figure out the number of shells with the period of element
- fill in in order using atomic number to figure out the number of electrons
- make sure the amount of electrons in the outer shell matches the group number

Question 5

metals

Answer 5

• the elements on the left of the zig-zag are all metals
• they conduct electricity because they allow charge to pass through easily
• metal oxides are basic, so they will neutralise acids. they dissolve to form solutions iwth pH of more than 7

Question 6

non-metals

Answer 6

right of zig-zag
- poor conductors of electricity
- nonmetal oxides are acific. so they will neuralise bases. dissolve in water to form solutoins with ph less than 7

Question 7

group 7 metals

Answer 7

the halogens are all inert (no react) because it takes a lot of energy to add or remove elecrtons from a noble gas atom
- they exist as single atoms

Question 8

Ions

Answer 8

form when atoms loose or gain electrons
they are charged particles as there are no longer the same number of electrons and atoms

negative ions (anions) form when atoms gain electorns - they have more electrons than protons
positive ions (cations) form when atoms loose electrons - they habe less electrons than protons

Question 9

predicting ions

Answer 9

Metals - lose electrons to form positive ions
Non-metals - gain electrons to form negative ions
elements in same group will form ions with the same charge

Question 10

The ions you memorise cdbakdsjch

Answer 10

Ag⁺
Cu²⁺
Fe²⁺
Fe³⁺
Pb²⁺
Zn²⁺
Hydrogen: H⁺
Hydroxide: OH⁻
Ammonium: NH4⁺
Carbonate: CO3²⁻
Nitrate: NO3⁻
Sulfate: SO4²-

Question 11

Ionic Compound

Answer 11

• when a metal and non-metal react together the metal atom looses electrons to form a positive ion (cation) and the non-metal looses them to form a negative ion (anion)
• the oppositely charged ions are strongly attracted to each other by electromagentic attractions called ionic bonds

Question 12

working out formula of an ionic compound

Answer 12

they have a overall charge of 0 so all the negative charges must balance the poitive charges
- use charges of individual ions to work out formula for the ionic compound

Question 13

Ionic Compounds structure

Answer 13

they have a lattice structure
- compounds with ionic bonding always have compound ionic structures
- ions are held together in a closely packed 3D lattice arrangement by attration of oppositely charged ions
- the electrostatic attraction is very strong and due to the enormous amount of energy needed to overcome this attraction, ionic compounds have high melting an bioling points
- they are not electrical conductors as solids but if they are melted or dissolved they are able to conduct electricity

Question 14

covalent substances

Answer 14

they share a pair of electrons with other atoms, which provides an extra shared electron for each atom
in covalent bonding there is a strong electrostatic attraction between the negitevely charged shared electrons and the poitively charged nuclei of atoms involved

Question 15

Important examples

Answer 15

H2
Cl2
HCl hydrogen chloride
NH3 ammonia
N2
H20
O2
CO2
CH4 - methane
C2H6 - ethane
CH3Cl - chloromethane
C2H4 - ethenes

Question 16

simple molecular substances

Answer 16

-atoms within a substance are held together by very strong covalent bonds
- however the forces of attraction between molecules are very weak, so the melting and boiling points are very low, as they are easily separated
- intermolecular forces are stronger between molecules with higher Mr as there are more points along the molecule for these intermolecular forces to act, so more energy is needed to break the force
- due to the increasing strength of forces melting and boiling points of simple molecular substances increase as Mr increases
- most molecular substances are gases or liquids at room temp, or even a easily melted solid

Question 17

giant covalent structures

Answer 17

similar to great ionic structures except there are no charged ions
- all atoms are bonded between each other by strong covalent bonds
- lots of these bonds means it takes a lot of energy to break them so very high boiling and melting points
- dont conduct elecricity, not even when molten
- usually insoluble in water

Question 18

diamond: giant covalent structure

Answer 18

• made up of a network of carbon atoms that each form 4 covalent bonds
• lots of energy needed to break these bonds so high melting point
• covalent bonds hold atoms in very rigid lattice structure, so its really hard
• doesnt conduct electricity as there are no free electrons or ions

Question 19

giant covalent structre: graphite

Answer 19

• each carbon molecule forms 3 covalent bonds, creating layers of carbon atoms, only held together weakly by intermolecular forces, so free to slide past each other, making graphite soft and slippery
• high melting boint - lots of energy to break bonds
• only 3/4 of each carbon’s 4 outer electrons are used in bonds so each carbon atom has one electron thats delocalised (free) and can move. So its a non-metal that conducts electricity

Question 20

C60 Fullerene: simple molecular substance

Answer 20

• c60 fullerene molecules are hollow spheres made up of 60 carbon atoms
• unlike diamond and graphite, it isnta a giant covalent structure, its just made of large covalent molecules
• c60 are held together by intermolecular forces so they can slide over each other, so the material is soft
• like graphite, each carbon in C60 fullerene has one delocalised electon, haowver the electrons cant move between the molecules so its a poor conductor of electricity
• solid at room temp