Topic 1 - Periodic table

In the past, how were elements categorised?

1. Their physical and chemical properties

2. Their atomic weight

Why did they categorise like this?

Scientists had not discovered the atomic structure of protons, neutrons or electrons.

When and what did Dmitri Mendeleev do?

In 1869, he made his own table of elements using an order of atomic weight. He left gaps and predicted new elements.

Why was Mendeleev’s table of element good compared to other tables at that time?

Because he took into account their physical and chemical properties and not just their atomic weight

How is the present periodic table of elements ordered?

Increasing atomic (proton) number

What elements form groups?

Elements with similar properties

What does the group number tell us? But with the exception of…

How many electrons in the outer shell. But with the exception of group 0 that contains helium which has 2 electrons in its outer shell - but the rest have a full outer shell.

Each new row on the periodic table represents what?

Another full shell of electrons

What are metals in terms of ions?

Are elements that form positive ions when they react.

Why do atoms react?

To form a full outer shell via losing, gaining or sharing electrons

Physical properties of metals?

1. Strong

2. Malleable

3. Great conductor of heat and electricity

4. High boiling and melting points

5. Dense

6. Shiny

Physical properties of non metals?

1. Dull

2. Brittle

3. Aren’t good conductors of electricity

4. Lower density

Where can transition metals be found on the periodic table?

In the middle of group 2 and group 3

Characteristics of transition metals

1. Properties of typical metals

2. Colourful

3. Can have more than one ion

4. Make good catalysts

What type of metals are in group 1?

Alkali metals

Characteristics of alkali metals?

1. Soft

2. Low density

3. Have one electron in their outer shell

Why are alkali metals so reactive?

Have only one electron in their outer shell

What are the trends of Alkali metals?

As you go down group 1:

1. Increasing reactivity

2. Lower melting and boiling points

3. Higher relative atomic mass

Why does the reactivity increase down group 1?

The outer electron is more easily lost as the attraction between the nucleus and electrons decreases as there are more full shells of electrons as you go down the group.

What compound is formed when Alkali metals react with non-metals?

Ionic compounds that are usually white solids that dissolve in water to form colourless solutions

What happens when group 1 metals react with water?

React vigorously - metal + water = metal hydroxide + hydrogen

What happens when group 1 metals react with chlorine?

1. Reacts vigorously when heated with chlorine gas to form white chloride salts

2. Metal + chlorine = metal chloride

What happens when group 1 metals react with oxygen?

Metal + oxygen = metal oxide

Compare the properties of Group 1 metals and transition metals

1. Group 1 metals are much more reactive

2. Group 1 are much less dense, strong and hard than transition metals

3. Group 1 metals generally have lower melting points compared to transition metals

Why are alkali metals called alkali metals?

They react with water to give alkaline solutions

What are group 7 elements?

Halogens - are all non-metals with coloured vapours that exist as diatomic molecules

What are the trends of The halogens?

As you go down group 7:

1. They become less reactive

2. Higher melting and boiling points

3. Higher relative atomic masses

Why do halogens become less reactive as you go down the group?

It’s harder to gain an extra electron, because the outer shell’s further from the nucleus, so less attraction.

How do Halogens share electrons with other non-metals?

Covalent bonding

Can a displacement reaction occur between group 7 elements?

Yes - a more reactive halogen will displace less reactive one

What are the group 0 elements?

Noble gases - are all inert, colourless gases

What is their atomic structure?

They exist as monatomic gases (single atoms not bonded to each other)

So if they are inert….

They’re non-flammable

What are trends of noble gases?

As you go down the group:

1. Increases the boiling points

2. Increasing relative atomic mass

Why does the boiling point increases as you go down the group?

Due to an increase in the number of electrons in each atoms, there are greater intermolecular forces between that are needed to be overcome.