Chapter 12 - The Periodic Table Flashcards
What is the purpose of the periodic table?
Its a way of classifying the elements
In what order is the periodic table arranged?
Shows elements in order of their proton number
What is PERIODICITY?
When elements with similar properties appear at regular intervals
What are the columns called
groups
What are the rows called?
Periods
What does the group number correlate to?
Same as the number of outer-shell electrons
What are the outer-shell electrons called?
valency electrons
Why are valency electrons important?
They dictate how an element behaves
Why do elements in the same group have similar reactions?
have the same number of valency electrons
Do group 0/8 elements react?
Why?
NO
- have a very stable electron arrangement
- are unreactive
- full outer electron shell
What does the period of an element tell you?
Tells you the number of electron shells the atom has
What is the nucleon number?
Total number of particles in the nucleus
protons + neutrons
Group 1 different name
alkali metals
Group 2 different name
alkaline earth metals
Group 7 different name
halogens
Group 8/0 different name
noble gases
What percentage of the elements are metals?
over 80%
Why is hydrogen alone in the periodic table?
Properties
- has 1 valency electron
- forms a positive ion (H+)
- similar to group 1 metals but it is A GAS
- reacts like a non-metal
Revise the properties of metals and non-metals
yes
What are artificial elements and why can they not be found in nature?
- elements made in a lab
- are radioactive and their atoms break down very quickly
list the group 1 metals
lithium, sodium, potassium, rubidium, caesium, francium
list the physical properties of group 1 metals
4
- good conductors of heat and electricity
- softer than most other metals (can cut with a knife)
- low density (float on water) ctom
- low melting and boiling points ctom
ctom - compared to other metals
trends in softness g1
softness increases going down the group
trends in density g/cm3 g1
density increases going down the group
trends in melting point g1
mp decreases going down the group
trends in reactivity g1
reactivity increases going down the group
lithium reaction with water
floats and fizzes
sodium reaction with water
shoots across the water
potassium reaction with water
melts with the heat of the reaction, hydrogen catches fire producing lilac flame
Overall description of group 1 metals with water
Alkali metals react vigorously with water.
Hydrogen bubbles off, leaving solutions of their hydroxides, which are alkalis.
chemical equation of lithium/sodium with water
2Na + 2H20 –> 2NaOH + H2
2Li + 2H2O –> 2LiOH + H2
etc
Overall description of group 1 metals with chlorine
If you heat the 3 metals and plunge them into gas jars of chlorine, they burst into flames.
Burn brightly forming chlorides
Overall equation for group 1 metals with chlorine
2Li + Cl2 –> 2LiCl
2Na + Cl2 –> 2NaCl
Overall description of group 1 metals with oxygen
Burst into flames when heated and plunged into gas jars of oxygen
Form oxides
Are group 1 oxides acidic or alkaline
alkaline
- dissolve in water to form alkaline solutions
Why are group 1 metals the most reactive?
- have only 1 valency electron
- strong drive to react with other elements and compounds, in order to give up this electron
- lose electron to form ions
What compounds do g1 metals make?
IONIC compounds
What charge do all the ions in group 1 have?
+1
What colour are group 1 compounds?
What colour do they form when they dissolve?
white solids
colourless solutions when dissolved in water
Why does reactivity increase going down group 1?
- in reactions, group 1 atoms lose their outer electron to gain a stable outer shell
- the more shells there are, the further the valence electron is from the positive nucleus - easier to lose
- easier the valence electron is to lose, more reactive a metal will be
List group 7 elements
fluorine, chlorine, bromine, iodine
3 properties of halogens
- form coloured gases
- are poisonous
- for diatomic molecules (containing 2 atoms)
What colour is … in gaseous form?
- fluorine
- chlorine
- bromine
- iodine
- pale yellow
- green
- red
- purple
Trend for colour for halogens
colour gets deeper going down the group
Trend for denisty for halogens
density increases going down the group
Trend for bp for halogens
the boiling point increases going down the group
Trend for reactivty for halogens
reactivity DECREASES going down the group
Overall reaction for halogens with metals
React to form halides
Fluorine reaction with iron wool
Iron wool bursts into flames
- no heating required
chlorine reaction with iron wool
hot iron wool glows brightly
bromine reaction with iron wool
hot iron wool glows, less brightly
iodine reaction with iron wool
hot iron wool shows a faint red glow
Why are the halogens so reactive?
- need just one more electron to reach a stable outer shell
- strong drive to react with other elements or compounds to gain this electron
- they accept electrons (w/metals) / share them (w/non-metals)
Why does reactivity decreases going down group 7?
- halogen atoms react to gain or share an electron
- positive nucleus of the atom attracts the electron
- more outer shells there are, further, the outer shell is from the nucleus
- attracting an electron becomes difficult
Overall rule for halogen reactions with halides
A halogen will displace a less reactive halogen from a solution of its halids
Cl2 + 2KBr –> 2KCl + Br2
Group 8/0 list elements
helium, neon, argon, krypton, xenon
properties of noble gases (5)
- non-metals
- colourless gasses
- occur naturally in air
- MONOATOMIC - exist as single atoms
- unreactive
Why are noble gases monoatomic and unreactive?
Their elements already have a stable outer shell
Where do we get the noble gases from?
Fractional distillation of liquid air
- helium is obtained from natural gas (it’s an impurity)
trend in atoms for group 8
atoms increase in size and mass going down the group
trend in density for group 8
density of gas increases going down the group
trend in boiling point for group 8
the boiling points increase going down the group
What does the increase in boiling points show?
A sign of increasing attraction between atoms
- harder to separate them to form a gas
What happens when a current is passed through noble gases at a low pressure?
They glow
Uses for helium
- used to fill balloons and airships
- won’t catch fire and lighter than air
Uses for argon
- used to provide an inert atmosphere
- as a filler in tungsten light bulbs
- to protect metals that are being welded
Uses for neon
- used in advertising signs
- glows red
- colour can be changed by mixing with other gases
uses for krypton
- used in lasers
e. g eye surgery / car headlamps
Uses for xenon
- gives a bright light with a blue tinge
- used in lighthouse lamps
- lights for hospital operating rooms
- car headlamps
What are the transition elements?
Block of 30 elements in the middle of the periodic table.
Physical properties of transition metals (5)
- hard, tough and strong
- high melting points (mercury is an exception)
- malleable, ductile
- good conductors of heat and electricity
- high density
which metal is the best conductor?
silver
and then copper
Chemical properties of transition metals (6)
- much less reactive than group 1 metals
- show no clear trend in reactivity
- most transition elements form coloured compounds
- most can form ions with different charges
- form more than one compound with another element
- most can form complex ions
In general, do transition elements corrode easily?
No
- iron is an exception - it rusts easily
What is the name for elements that form many ions with different charges?
They have a VARIABLE VALENCY
How do you make salt of a transition element?
react their oxide/hydroxide with acids
their oxides are basic and react with acids to form salts
What do the roman numerals in brackets tell you? e.g (II)
- how many electrons the metal atom has lost
- OXIDATION STATE
Uses of the transition elements? (4)
- used in structures such as bridges, buildings, cars.
- used in making alloys
- used as conductors of heat and electricity e.g copper for electric wiring
- most act as catalysts e.g iron is used in making ammonia
What transition element is most commonly used in making structures?
Iron is most widely used usually in the form of alloys called steels
what is an alloy?
Small amounts of other substances are mixed with a metal to improve its properties
What is used to create stainless steel?
chromium and nickel
Trends across the periodic table (left to right)
2
- go from metals to non-metals
- mp and bp rise to the middle of the period (IV), then fall to very low values on the right
What type of conductors are metalloids known as?
Semi-conductors
What does valency mean?
The valency of an element is the number of electrons its atoms lose, gain or share, to form a compound
What does the valency match?
- number of valency electrons (up to group IV)
- matches the charge on the ion, where an element forms ions
Rules for electron transfer for metals and non-metals
metals - lose their outer electrons
non-metals - gain or share electrons
trends in reactivity for non/metals
- reactivity
decreases across metals - reactivity increases for non-metals
across the periods
Why does reactivity decrease for metals across the period?
The more electrons a metal atom needs to lose, the more difficult it is (must have enough energy to overcome the pull of the nucleus)
Why does reactivity increase for non-metals across the period?
(except group 0)
The fewer electrons a non-metal needs to gain, the easier it is to attract them
