Chemistry - 2. the periodic table

How are elements arranged?

By atomic number

Elements in the same group have similar what?

similar chemical properties

What did Johan Dobereiner discover?

- triads
- elements with similar chemical properties often came in 3’s

What did John Newlands discover?

- law of octaves
- every 8th element reacted similarly
- ordered in atomic weight but some didn’t fit the pattern

What 3 things did Dimitri Mendeleev do to the periodic table?

- he ordered the elements in atomic weight
- he rearranged any elements that did not fit the pattern
- he left gaps for undiscovered elements

What group was originally not in Mendeleev’s table?

Group 0

Why might elements come in the wrong order when ordered by atomic weight?

Isotopes

What is group 1?

Alkali metals

What is group 7?

Halogens

What is group 8?

Noble gases

Properties of metals

- conductors of heat & electricity
- malleable
- high melting & boiling points
- high density
- shiny

Properties of non metals?

- not conductors of heat & electricity
- brittle
- low melting & boiling points
- low density
- dull

Are group 0 elements reactive of unreactive?

unreactive

Why is group 0 unreactive?

They have a full outer energy level which means they are stable

What state are they at room temperature?

gas

What is the trend of density down group 0?

It increases

What is the trend of melting & boiling points down group 0?

It increases

Why are group 0 elements used for welding and food packaging?

The are unreactive so create an inert atmosphere so unnecessary reactions occur

Give 3 examples of group 0 elements?

He, Ne, Ar

How many electrons do group one elements have in their outer shell?

1

How do group 1 elements react with water?

they react very vigorously

What happens to water when a group 1 metal has reacted with it?

It becomes and alkali

What is the trend in density down group 1?

It increases

What is the trend in melting & boiling points in group 0?

It decreases

What compound is formed when a metal reacts with a non metal?

Ionic compound

What gas is formed when an alkali metal reacts with water?

hydrogen