periodic table, alkali metals + halogens

why are noble gases inert

they have a complete outer shell, so don’t need to react

why is argon used for food packaging

unreactive, not toxic

why is argon used for welding

unreactive and not flammable

properties unique to alkali metals

• very reactive with oxygen and water- stored in oil

• shiny when cut, quickly dulls

• low density (some float on water)

• low melting point for a metal

• mainly form white compounds which are soluble in water

why do alkali metals have similar properties

they all have 1 outer shell electron, and react by losing it

observation of lithium and water

fizzes, floats on surface, gently moves, disappears (universal indicator turns purple)

sodium and water is same as lithium but…

melts into a ball, moves faster

potassium same as sodium but…

moves faster, lilac flame and sparks (H igniting)

why do alkali metals get more reactive as you go down group

• react by losing outer electron

• as you go down, atoms get larger

• this means electron is further away from nucleus

• there is less attraction

• electron is lost more easily

halogen are __ non metals and are all _

reactive

toxic/harmful

fluorine state + colour

gas , pale yellow

chlorine state + colour

toxic gas, pale green

bromine state + colour

volatile liquid, red-brown

iodine state + colour

brittle solid, dark grey

astatine state + colour

solid black

halogen ions are

halides

hydrogen chloride state , solubility, what happens in water?

gas, soluble, dissociates in water to form hydrochloric acid

how to halogens react?

gain an electron

why do halogens get less reactive going down group

• atoms get bigger

• outer electron further from nucleus

• attraction is weaker

• extra electron is less easily gained

group no.

number of electrons in outer shell

period no

number of shells