C9 - The periodic table

elements with similar properties occur at regular intervals and happen ‘periodically’

Elements in the same group (column) have the same number of electrons in their outer shell. Elements in group 2 have 2 electrons in outer shell Elements in group 3 and 3 electrons in outer shell and so on. Rows are also called periods Each new row an element has one more shell of 8 electrons.

left of the periodic table

right of the periodic table

alkali metals

Reactivity increases as you go down the group Soft to cut Shiny Very low MP compared to most metals. MP decreases going down the group Low density React easily with air and water

because they only have one electron in their outer shell which they want to give away when reacted with a non metal. The more electrons a metal atom has to lose the more energy needed to start the reaction. Therefore group 2 is less reactive than group 1 as they have to lose 2 electrons

When burned Lithium - red sodium - orange/yellow potassium - lilac In water metals react vigorously giving off lots of effervescence. Lithium - fizzes steadily and floats becoming smaller until it disappears Sodium - Fizzes rapidly and melts to form a ball on the water surface Potassium - Ignites and creates a mini explosion Chlorine: React easily, burning in chlorine to form a white solid

lithium + oxygen ==> lithium oxide 4Li + O2 ==> 2Li2O lithium + water ==> lithium hydroxide + hydrogen 2Li + 2H2O ==> 2LiOH + H2 lithium + chlorine ==> lithium chloride 2Li + Cl2 ==> 2LiCl

halogens

Exist as diatomic molecules (contain 2 atoms) Reactivity decreases going down the group 7 electrons in outer most shell Florine - pale yellow gas Chlorine - pale green gas Bromine - red-brown liquid Iodine - black solid

Dissolved in water forming solutions behaving like bleach Chlorine solution - pale yellow Bromine solution - orange Iodine solution - yellow/brown Halogens form salts with metals Displacement reactions: More reactive halogen will displace a less reactive one from a solution of a salt.

chlorine + water ==> hydrochloric acid + chloric acid Cl2 + H2O ==> HCI + HCIO iron + chlorine ==> iron(III) chloride 2Fe + 3Cl2 ==> 2FeCl3 Chlorine + sodium bromide ==> sodium chloride + bromine Cl2 + 2NaBr ==> 2NaCl + Br2

as the atoms get bigger and electrons get further away from nucleus the electrostatic attraction gets weaker so they lose the one electron easier

as outer shell gets further away from nucleus the electrostatic attraction gets weaker meaning its harder to gain an electron meaning it will be less reactive as it becomes stable.

middle of the periodic table

Greater strength and hardness Higher density Higher MP and BP Lower reactivity

Can form different positive charges i.e Cu+ Cu2+ Fe2+ Fe3+ Very colorful Often used as catalysts Little to no reaction with water, air or acid

noble gases

Inert because they have a stable full outer shell (Can be used in lightbulbs as not reactive) Monatomic (exist as single atoms) Low BP and MP but increase going down the group as the relative atomic mass increases Low density (can be used as balloons)

Florine = used as toothpaste Chlorine = sterilization of water Bromine = pesticides and plastics Iodine = sterilizing wounds

Helium (lighter than air) = zeppelin and balloons Neon = lights Argon = used in lamps Xenon = flashlights

Iron = Haber process for making ammonium Rhodium and platinum = used as catalytic converters in cars