Periodicicity

2025 Exams SL & HL topics

number of electrons in outer shell

What is related to the group number?

amount of shells in element

What is related to the period number?

Alkali metals

What does group 1 consist of?

• very reactive

• bond by loosig 1 electron to become +1 ions

Reactivity of group 1 metals?

• soft

• light

Properties of group 1 metals?

Ionisation Energy

IE stands for

decreases down the group

• as there are more shells, theres a greater distance between nucleus and electrons, leads to a weaker attraction

IE of group 1 metals, reasoning?

increases down the group (more shells)

Atomic Radius of group 1

½ distance between two nucleai

how is atomic radius mesured?

decreases down the group, bonding becoes weaker down the group

melting point in group 1 metals?

charge = +1

when group 1 metal becomes an ion it looses 1 electron which is in its outer shell, therefore loosing the whole shell, this leads to a stronger pull by the nucleus that has more protons than electrons in shells (pulls them in closer)

Why is there a large difference between the ionic radius and atomic radius of group 1 metals?

½ distance between two nucleais of two IONS

How to mesure ionic radius

endothermic

larger distance from nucelus, weaker attraction/pull

Electron Affinity of group 1 metals?

energy involved in making 1 mol of gaseous anions from 1 mol of gaseous atoms

Define Electron Affinity (EA)

attraction of nucelus to the pair of electrons forming a covalent bond

define electron negativity

• shiny but turns dark when oxidized

• soft

Description of Lithium (Li)

• Fizzes and floats (less dense than water)

• produces hydrogen gas

• turns litmus paper blue - water’s gone alkaline

How does Li react with water?

sodt silvery-white metal

Description of Sodium (Na)

• Fizzes

• Dissapears

• turns sphirical (ball)

• heat released from reaction melts sodium

Reaction of Na and water

the heat lights up the sodium as the paper prevents it from moving around the water, casuing so much friction and heat to focus on one spot, setting sodium on fire

Reaction of Na and water WITH filter paper

• soft

• white-silvery

Description of Pottasium (K)

• bursts into flame

• lilac flame

• releases large amounts of heat

• releases hydroxide and hydrogen

Reaction of K and water

Hallogens

F, Cl. Br, I

What does group 17 consist of?

• reactivity decreases going down the group

• Top of group more reactive than bottom

• Form negative ions!!

  (opposite of group 1)

• gain electron (-1) ion

• HIGHLY REACTIVE

Reactivity of group 17

small atom=small distance to travel=lower energy needed=high released energy

when solid turns into gas (no liquid stage)

Define sublimation

green gas (sublimation)

Chlorine (Cl) at room temperature

red liquid (one of 2 liquid elements)

volatile liquid (easily turns into gas)

Bromine (Br) at room temperature

grey solid

solid but sublimes easily into gas

Iodine (I) at room temperature

gets darker

WHat is the colour change as you go down the group 17?

they’re non-polar

Why are hallogens more soulable in hexene than water?

whoops

Reactions

• Higher than Atomic Radius as theres more electrons than protons

• attraction spreads out across more electrons making the pull weaker so the radius expands

  (loop on cows becomes too loose)

Ionic Radius vs Atomic Radius in group 17

• diatomic molecules (covalent, exist as a pair)

• intermolecular forces increase DOWN the group

  (when a gas = force weaker)

• london forces increase down the group

Group 17 Melting point

decreases down the period

Atomic radius in Period 3

increases across group

Electronegativity in period 3

• not enough substance

• substance isn’t soulable in water

What could cause a false neutral pH result?

• yellow flame

• white smoke

• blue → alkaline

• produces 2NaOH

Na reaction with oxygen(and water) +pH indicator

• bright pale yellow flame

• white smoke

• red → acidic

Red P reaction with oxygen (and water) +pH indicator

• amphoteric oxide

• white glow

• litmus → green

  (should be alkaline but it isn’t soulable in water)

Al reaction with oxygen (and water) + pH indicator

• no reaction

• can’t dissolve should be acidic

• was neutral

Si reaction with oxyfen (and water) + pH indicator

sparkiling

• purple → alkaline

Cl reaction with water and oxygen

produces magnesium hydroxide

weak bluesh

slightly soulable

alkaline

reaction of Mg with oxygen (and water)