Lecture 3 - The Periodic Table of Elements

Question 1

Describe the law of the triads

Answer 1

organised by atomic weight into groups of 3, the middle element would have an atomic weight as an average of the two elements either side

Question 2

Describe the law of octaves

Answer 2

organised in groups of 7 by increasing atomic weight which would have similar physical and chemical properties

Question 3

what is the periodic law?

Answer 3

properties of elements are periodic functions of their atomic numbers

Question 4

what are the 8 classifications of the periodic table

Answer 4

• alkali metals
• alkaline earth metals
• transition metals
• lanthanides
• actinides
• noble gasses
• nonmetals
• metalloids

Question 5

Describe the alkali metals

Answer 5

• group 1
• silver coloured soft metals that can be cut with a knife
• highly reactive and rarely found in elemental form in nature

Question 6

Describe alkaline earth metals

Answer 6

• group 2
• sliver coloured soft metals
• reactivity similar to alkali metals

Question 7

Describe the noble gasses

Answer 7

• group 8
• chemically inert
• non-metalic gaseous at standard condition

Question 8

Describe the halogens

Answer 8

• group 7
• highly reactive and toxic
• gases or low boiling point/melting point materials

Question 9

Describe metalloids

Answer 9

• 6 elements - boron, silicon, arsenic, germanium, antimony, tellurium
• properties of metals and non metals
• semi conductors

Question 10

Describe transition metals

Answer 10

• an element with at least one oxidation state has a partially filled d-subshell
• valencies are variable and they readily undergo oxidation and reduction

Question 11

Describe lanthanides

Answer 11

• 15 elements with atomic numbers 57-71
• also known as rare earth metals
• shiny and silvery white and stain easily when exposed to air
• have high melting and boiling points

Question 12

Describe actinides

Answer 12

• 15 elements with atomic numbers 89-103
• radioactive
• very dense metals with distinctive structures
• numerous allotropes may be formed
• combine directly with most non metals

Question 13

Describe non metals

Answer 13

• groups 14-16
• cant conduct very well
• very brittle and not ductile/ malleable
• have no metallic cluster and don’t reflect light

Question 14

what are valence electrons?

Answer 14

the number of electrons in the outer shell of a atom is unchanged on moving down a given group

Question 15

Describe valencies for groups on the periodic table

Answer 15

1-4 valency is equal to group number

4-8 valency is equal to 8- group number

Question 16

what is valency?

Answer 16

the maximum number of univalent atoms that may combine with an atom of the element under consideration or with a fragment or for which an atom of this element can be substituted