Section 4
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how do alkali metals react when they are put in water?
they all react vigorously (in a similar way)
what does the reaction between alkali metals and water produce?
a metal hydroxide solution (which is alkaline)
why are group 1 elements known as the alkali metals?
because they form an alkaline metal hydroxide solution
what does the reaction of alkali metals with water also produce?
hydrogen - this is why you can see fizzing
which elements in group 1 are most reactive?
group 1 elements become more reactive down the group as the atomic number increases
how can you tell that alkali metals become more reactive?
the rate of reaction with water increases
name 3 alkali metals.
Lithium (Li), Sodium (Na), Potassium (Ka), Rubidium (Rb), Caesium (Cs), Francium (Fr)
what are the properties of alkali metals?
• soft • low density • low melting point
what are the properties down the group of alkali metals?
• they are more reactive • their boiling point decreases
why are alkali metals so reactive?
• they all have one electron in their outer shell • further down the group the radium of the atoms get bigger • the outer shell is further away from the positive nucleus • positive nucleus holds outermost electron in place • the distance weakens the attractive force
how are group 7 elements called?
halogens
as the atomic number of halogens increases…
• the less reactive • the elements have a darker colour • higher boiling point
which halogens are most reactive?
higher up group 7 elements are more reactive
whats the colour and physical state at room temperature of chlorine?
• green • gas
whats the colour and physical state at room temperature of bromine?
• red-brown • liquid
whats the colour and physical state at room temperature of iodine?
• dark grey • solid
describe the boiling points of halogens.
the further down (the higher the atomic number) the higher the boiling point of the element
why are halogens further down less reactive?
they have more shells and the outer electrons are therefore further away from the positive nucleus meaning that the forces of attraction are weaker and its more difficult to gain another electron
which gases are found in the atmosphere?
• carbon dioxide • oxygen • argon • nitrogen
how much argon is found in the atmosphere?
1%
how much oxygen is found in the atmosphere?
21%
how much nitrogen is found in the atmosphere?
78%
how much carbon dioxide is found in the atmosphere?
0.04%
what kind of gas is carbon dioxide?
a greenhouse gas