The Periodic Table
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Who created the periodic table and when? How many elements did they sort ?
Dmitri Mendeleev in 1869 sorted 50 elements into what is known as the periodic table today.
How did Mendeleev sort the table?
By order of atomic mass while also placing elements with similar chemical properties in columns (groups).
How could he predict future elements?
The order meant that many gaps were left which meant that we could predict the properties of undiscovered elements.
Periodic table
A table of all known elements
How many elements do we think there are now?
100 (still discovering them now)
How do modern periodic tables order their elements?
Increasing atomic number
What does a group tell you?
Their properties and number of electrons in their outer shell.
What do periods tell you?
How many electron shells
Where’s the partition between metals and nonmetals on the periodic table?
Boron to astatine staircase
What’s on the left of the staircase?
Metals
What’s on the right of the staircase?
Nonmetals
Properties of metals
Conduct heat and electricity, sonorous, malleable, shiny, ductile
What’s a characteristic of a metal oxide?
They are basic, so will neutralise acids
What’s a property of a nonmetal oxide?
Acidic and will neutralise bases
What group are alkali metals? How does this affect their characteristics?
1, meaning there is only one outer shell electron. This means that they are very reactive as they readily donate their outer electron to maintain a full outer shell.
Alkali metal + water
> metal hydroxide + hydrogen
What are the properties of alkali metals?
They are soft (low density), have a low bp/mp and are dull coloured.
What happens as you go down group 1? Why?
Alkali metals increase reactivity, density & bp. This is because the bigger the atom is, the further the outer electron is from the nucleus. This means that there’s less force of attraction and so it is easier to remove the outer electron and so is more reactive.
Write out the balanced symbol equation for the reaction between potassium and water.
2K + 2H2O > 2KOH + H2
What type of reaction is the reaction of water and alkali metals?
It’s an exothermic reaction and the flame is the hydrogen on fire.
Why do the products of alkali metals and water turn out alkaline?
Because it produces a metal hydroxide.
What group are halogens?
7
What happens as you go down group 7?
They become less reactive, darker, more dense and higher bp/mp
Halogen properties
Low BP’s/MP’s Toxic, bleaching agents Nonmetals Disinfectants Very reactive Diatomic