c4 - predicting chemical reactions

what metals are known as the alkali metals

group 1

how many electrons do alkali metals have in their outer shell and what does this mean

1 electron so they all have similar chemical properties

what are the 3 physical properties of alkali metals

• low mp and bp

• low density

• very soft - can be cut with knife

why dont alkali metals form covalent bonds

they lose their 1 electron on their outer shell so easily that sharing it is out of the question

why does the reactivity of alkali metals increase down the group

• the atoms get bigger down the group

• the outer electron is further sway from the nucleus

• the further the electron is from the positive attraction of the nucleus , the easier it can be lost

what properties do alkali metals and normal metals share

• good conductors of heat + electricity

• shiny - only seen in alkali metals when freshly cut but then turn dull with oxidation

how does lithium (alkaline metal) react with water

it moves around the surface fizzing vigorously

whats the word equation for the reaction of lithium and water

2Li + 2H₂O → 2LiOH+ H₂

how does sodium (alkaline metal) react with water

move over top of water with vigorous fizzing and may catch fire with an orange flame

how does potassium (alkaline metal) react with water

moves over top of water with vigorous fizzing and may catch fire with lilac flame

how does rubidium react with water

they explode

where are halogens found

group 7

how many electrons do halogens have on their outer shell

7 electrons so they all have similar chemical properties

whats the trend of the size of each element and the number of full electron shells in group 7

• increase down the group

• means the outer shell is farther away from the nucleus and the positive protons are shielded by more electron shells

• the further the outer shell is from the positive nucleus, the harder it is to attract another electron

whats the trend of reactivity in group 7

reactivity decreases with the size of the atom (down the group)

how many more electrons do halogens need to become stable

• need 1 more atom

• achieves this when a halogen atom can receive an electron and forms a single covalent bond

whats the trend of the melting and boiling points in halogens and why

• they increase down the group as down the group the molecules become larger and the intermollecular forces become stronger

• more energy is needed to overcome these forces

whats a diatomic molecule

two atoms covalently bonded together in a molecule

are halogens diatomic molecules

yes because they share one pair of electrons in a covalent bond (e.g. Cl _{2 ,} Br _2, I_{2 )}

whats chlorine characteristics (halogen)

fairly reactive poisonous green gas (has low boiling point)

whats bromine’s characteristics (halogen)

posinous reddy brown liquid which gives off orange vapour at room temp

whats iodine’s characteristics (halogen)

dark grey crystalline solid which gives off purple vapour when heated

what are properties all halogens possess

• non metals - dont conduct electricity

• brittle and crumbly when solid

• poisonous and smelly

Halogens react with _______ to form salts.

alkili metals

what does the reactivity of an atom mean

how easy it is to lose or gain electrons - the easier it is the more reactive the atom

whats a displacement reaction

a reaction that occurs when a more reactive element replaces a less reactive element in a compound

whats the method for the experiment to compare the reactivity of halogens

1. place 2 drops of potassium chloride solution in each 3 dimples on your dimple tile

2. repeat with potassium bromide in the next row and potassium iodine in the final row

3. place 2 drops of chlorine water in each 3 dimples down left hand column of dimple tile

4. repeat with bromine water and iodine water in the next columns

5. observe if there is a colour change with either chlorine, bromine or iodine

how do you tell in the experiment for reactivity trends of halogens which is most reactive

• the order of reactivity is: chlorine > bromine > iodine.

• because chlorine could displace bromine and iodine, bromine could only displace iodine, but iodine could not displace chlorine or bromine.

how do you tell by observing is a halogen has been displaced in an experiment

if you see a colour change then a reaction has heppaned ad the halogen has replaced teh halide ions in the salt

what are the colours of halide salts, bromide, chlorine and iodine

• Halide salts (e.g. KCl, KBr, KI) are colourless

• Bromine water is orange

• Chlorine water is colourless

• Iodine water is brown

what is the name for all the gases in group 0

noble gases

what can be said about all the noble gases

• all colourless gasses at room temp

• all made up if single atoms

• all inert

• non flammable

what does inert mean

they are not generally reactive so they usually dont react with anything

why are all the noble gases inert

they have a full outer shell of electrons - dont easily give up / gain electrons

what are the properties of group zero

the boiling point , melting point ans density all increase as you go down the group

how metals react with _____ tells you about their reactivity

acids

whats the reactivity series

potassium

sodium

calcium

magnesium

aluminium

zinc

iron

copper

silver

what happens when you put a more reactive metal into a solution of a less reactive metal salt

the reactive metal will replace the less reactive metal in the salt