C2 The Periodic Table Flashcards
What is a column?
A group of elements with similar properties are grouped together
What is a row?
Periods (show how many electrons shells an element has)
What is an element?
A substance made of one type of atom that cannot be broken down into a more simple substance
The original Periodic Table (1808)
The understanding of atomic structure was poor. There were uncertainties between elements and compounds
John Dalton PT - 1808
Ordered elements by mass
He proposed that:
- Atoms cannot be broken down into anything smaller
- Atoms of a particular element are identical
- In chemical reactions, atoms are rearranged
John Newlands PT - 1864
Stuck with Dalton’s idea about ordering elements by mass
Discovered that there was a repeating pattern of properties for every 8th element (Law of octaves)
Law of octaves
Every 8th element has similar properties when arranged in the increasing order of their atomic mass
Dmitri Mendeleev PT - 1869
Kept mass order, but switched the position of elements if the properties did not match
He also left gaps for undiscovered elements
Henry Moseley - 20th century
Discovered atomic structure and protons
So the periodic table was put in order of proton (atomic) number
Properties of Metals
- Form positive ions
- Shiny
- Malleable
- High boiling and melting point
- Magnetic
- Mostly solids at room temperature
Properties of Non-metals
- Form negative ions
- Dull
- Brittle
- Low boiling and melting point
- Non-magnetic
- Mostly gases at room temperature
How do metals become ions?
Lose electrons to have a full outer shell of electrons. That would make them have more protons than electrons and therefore become positive ions
How do non-metals become ions?
Gain electrons and become negative ions. An exception to this is hydrogen which is a non-metal but forms positive ions
Which groups form positive ions and which form negative ions?
Positive ions: Groups 1,2 and 3
Negative ions: Groups 5,6 and 7
What are group 0 elements?
The noble gas. They have a full outer shell of electrons making them very stable. The boiling point of noble gases increases with increasing relative atomic mass (going down the table)
Why are they called alkali metals?
They form an alkaline solution when added to water
What is the trend in reactivity for alkali metals?
Gets more reactive as you go down the group
How do alkali metals react with oxygen in the air?
Forms metal oxide. This produces a layer of dull oxide on the surface of the metal
How do alkali metals react with heat and chlorine?
Burst into flames when heated and added to chlorine. They form metal chlorides.
What are alkali metals?
The elements in Group 1
What are halogens?
The elements in Group 7
What is the electronic structure of the halogens?
- Need 1 electron to have a full shell
- Form negative ions
- Similar properties
What are displacement reactions?
Occurs when a more reactive substance takes the place of a less reactive substance
A bit like the more reactive substance steals the compound from the less reactive substance
Displacement reactions of halogens
If a more reactive halogen is added to a solution of a compound, it will react with that compound to form a new one. The halogen is displaced.
Where can the transition metals be found on a PT?
Between Group 2 and Group 3 of the periodic table
What is an alloy?
- Made when metals are combined to give greater strength
- Mixture of 2 or more elements with at least one being a metal
Properties of transition metals
- Good conductors of electricity and heat
- Hard and strong
- High densities
- High melting points (except mercury)
- Much less reactive than the alkali metals
Compounds of transition metals
- Can make ions of different charges, e.g. Fe²⁺ or Fe³⁺
- Often make coloured compounds, e.g. Fe²⁺ compounds are green and Fe³⁺ compounds are reddish brown
