1.2 The periodic table Flashcards
1.2.1 The periodic table
How is the table arranged?
- In order of atomic number
- So elements with similar properties are in groups, and occur at regular intervals.
- Elements in the same group in the periodic table have the same number of electrons in the outer shell and this gives them similar chemical properties.
1.2.2 Development of the periodic table
Stage 1 of development
John Dalton
John Dalton: published a table of elements, orded in their atomic weights
atomic weight = atomic mass
1.2.2 Development of the periodic table
Stage 2 of development
John Newlands
His table was incompleted and some elements were placed in inappropriate groups if the strict order of atomic weights was followed
1.2.2 Development of the periodic table
Stage 3 of the development
Mendeleev
Left gaps for elements that he thought had not been discovered, and in some places changed the order based on atomic weights
1.2.3 Metals and non-metals
What do metals and non-metals form?
Metals form positive ions
Non-metals form negative ions
1.2.3 Metals and non-metals
Properties of metals and non-metals
Metals: Shiny, solid, dense, strong, malleable, good heat and electrical conductors
Non-metals: Dull, low density, weak, brittle, poor heat and electrical conductors
1.2.4 Group 0
Properties of group 0
Noble gases:
* Unreactive and do not easily form molecules because their atoms have a full outer shell already so are stable
* normally 8 electrons in outer shell (helium is an exception of 2 electrons)
1.2.4 Group 0
Trend of group 0
The boiling point of the gases increase, as the relative atomic mass increases
as you go down the group, BP increases
1.2.5 Group 1
Properties of group 1
Alkali metals:
* single electron in their outer shell - easy to lose and become stable
* very reactive, so stored under oil to prevent them from reactive to oxygen and water vapour in air
* low densities
* very soft
* silvery, shiny surface, but when cut, it goes dull due to the reaction with oxygen
* low MP and BP
* Lithiuium, sodium, potassium react vigorously with water: metal floats, moves around and fizzes
1.2.5 Group 1
Trend of group 1
- reactivity of elements increase as you go down the group
- atoms get larger, so electron on outer shell is attracted less, because distance increase
1.2.6 Group 7
Properties of group 7
Halogens:
* 7 electrons in their outer shell
* non metals - diatomic - covalent bond
* toxic and have coloured vapours
* poor conductors of heat and electricity
1.2.6 Group 7
Trend of group 7
As you go down the group, the higher the mass, melting point, boiling point.
As you go down the group, the reactivity decreases (harder to gain an electron when the atom gains more mass)
a more reactive halogen can displace a less reactive halogen
1.2.6 Group 7
Colour of elements at room temp
group 7 elements
Fluorine: pale yellow gas
Chlorine: poisonous green gas
Bromine: toxic red-brown liquid
Iodine: dark grey solid with purple vapour when heated
Astatine: black solid
