Atomic Structure and the Periodic Table Flashcards
Atom
The smallest part of an element that can exist
Radius of atom
0.1nm
Subatomic particles in atom nucleus
- protons
- neutrons
Radius of nucleus of atom
1 x 10⁻¹⁴ m
Size of atom nucleus to radius of atom
1/10000
Charge of nucleus of atom
Positive
Where is mass concentrated in atom
Nucleus
Where are electrons in atom
Orbiting nucleus on shells
Charge of proton
+1
Relative mass of proton
1
Charge of electron
-1
Relative mass of electron
1/1840
Charge of neutron
0
Relative mass of neutron
1
Charge of an atom
Neutral
Why is charge of atom neutral
Same of number of protons and electrons, their charges cancel out
What does atomic number tell you
Number of protons in an atom
What does mass number tell you about an atom
Number of protons and neutrons
How to find number of neutrons in an atom
Atomic mass — atomic number
Element
Substance made up of one type of atom
What decides what type of atom it is
Number of protons
How many elements are there
About 100
Isotopes
Atoms of an element with the same number of protons but a different number of neutrons
Relative atomic mass
Average mass of an element, taking into account all isotopes that make up an element
Relative atomic mass formula
sum of (isotope abundance percent X isotope mass number)
—————————————————
sum of all isotope abundance percents
Compound
Substances formed from 2 or more elements with the atoms in fixed proportions throughout the compound, held together by chemical bonds
How are compounds made
Elements reacting together
How are compounds separated into elements
chemical reactions
How are bonds made
Giving away, taking or sharing electrons
Ion
charged particles that have gained or lost electrons, making them positively or negatively charged
What happens to metal atoms in atomic bonding
- lose electrons
- form positive ions
What happens to non-metal atoms in atomic bonding
- gain electrons
- form negative ions
What does a compound formed of non-metals consist of
- molecules
- each atom covalently bonds to another
Mixture
Substance made from two or more elements or compounds that aren’t chemically bonded
How are mixtures separated
Physical methods
What are the physical methods
- filtration
- crystallisation
- simple distillation
- fractional distillation
- chromotography
Air
Mixture of gases, mainly nitrogen, oxygen, carbon dioxide and argon, easily separated
Properties of a mixture
Mixture of properties of separate parts
Paper chromatography practical
- draw baseline in insoluble pencil 1cm from bottom of the paper
- add ink spot to line and place paper in solvent, not touching ink
- place lid on container to stop evaporation
- solvent seeps up paper
- dyes move up paper at different rates, seperating
- if dyes are insoluble they stay on baseline
- taken paper out of beaker to dry
- have a chromatogram
When is filtration used
- to separate an in insoluble solid from a mixture
- purification
Filtration
- fold filter paper into cone and place in funnel
- place funnel in conical flask
- pour solution through
- substrate filters through, residue left in filter paper
Methods of separating soluble solids from solutions
- evaporation
- crystallisation
How to separate through evapouration
- pour solution into evaporation dish on tripod
- slowly heat using Bunsen burner
- solvent will evaporate, solution will get more concentrated, crystals will form
- keeping heating until only dry crystals remain
How to separate through crystallisation
- pour solution into evaporating dish and gently heat
- as solvent evaporates, solution’s concentration increases
- remove dish from heat, leave to cool
- salt forms crystals as it becomes insoluble in cold, highly concentrated solution
- filter solutions and leave to dry
When is crystallisation/evaporation used
To separate a soluble substance from a solution
Rock salt
Mixture of salt and sand
How to separate rock salt
Filtration
Why can rock salt be filtered
Salt dissolves in water and sand doesn’t
What does distillation separate
Mixtures containing liquids
Types of distillation
- simple
- fractional
What does simple distillation separate
Liquid from a solution
Simple distillation practical
- solution is heated in conical flask with thermometer and bung
- part of solution with lowest boiling point evaporates
- vapour turns back into liquid in condenser as it is cooled by water
- distilled liquid goes in beaker
- rest of solution left is flask
When is fractional distillation used
In a mixture of liquids with similar boiling points
Fractional distillation practical
- put mixture in conical flask with fractioning column filled with glass rods
- liquid with lowest boiling point evaporates first
- when thermometer reaches that temp, liquid reaches top of column
- column cooler towards top, other liquids won’t get all the way up column
- when first liquid collected, raise temp until next reaches the top
Which electron shells are filled first
Lower ones - close to the nucleus
How many electrons go on the first shell
2
How many electrons go on every shell after the first
8
How did elements used to be categorised
- atomic weight
- chemical/physical properties
When was Mendeleev’s periodic table
1869
How was Mendeleev’s periodic table arranged
- mainly order of atomic weight
- elements would be switched it properties meant it should be changed
- gaps left for undiscovered elements
How was Mendeleev’s periodic table proven right
- elements were discovered to fill gaps, fitting the pattern
- isotopes were discovered - showed he was right not to place elements in order of atomic weight, isotopes have different masses but same chemical properties so have same position of periodic table
How are elements ordered on periodic table
Increasing atomic number
Why are elements arranged in increasing atomic number on periodic table
So there are repeating patterns of properties of elements that occur periodically
Where are metals on the periodic table
Left
Where are non-metals on the periodic table
Right
What are the vertical columns on periodic table
Groups
What does group number tell you on the periodic table
Number of electrons in outer shell
Relationship between reactions of elements in same group
React in similar way
What are the rows in the periodic table
Periods
What does period number tell you on periodic table
Number of electron shells
What type of element are most on periodic table
Metals
Why do elements generally react
To form a full outer shell
Which elements react easiest
- metals to the left of the periodic table
- metals to bottom of periodic table
Why do metals to left of periodic table react easiest
Less electrons to remove
Why do metals to bottom of periodic table react easiest
- less electron shells
- less shielding between nucleus and outer shell electrons
- less attraction between nucleus and outer shell electrons
- not much energy required to remove electrons
Why is it harder for non-metals to react and form positive ions
- more electrons on outer shell needing more energy to remove
OR - less electron shells so less shielding and more attraction between nucleus and outer shell electrons, more energy needed to remove
Why don’t metals and non-metals have similar properties
Non-metals don’t have metallic bonding
Properties of metals
- malleable
- high melting/boiling points
- good conductors of electricity
- good conductors of thermal energy
Properties of non-metals
- dull looking
- more brittle
- not always solid at room temperature
- generally conduct electricity
- usually have lower density
Group 1 elements
Alkali metals
Group 1 chemical properties
- 1 electron in outer shell
- very reactive
- reactivity increases as you go down the group
- higher relative atomic masses
Group 1 physical properties
- soft
- low density
- generally white solids
- generally dissolve in water to form colourless solutions
What happens when group 1 metals form ionic compounds
- lose their 1 outer shell electron to form a full outer shell
- form 1+ ions
What happens when group 1 metals are put in water
- react vigorously - reaction becomes more vigorous down group
- float + move around on surface, fizzing vigorously
- produce hydrogen gas
- form hydroxides that dissolve in water to give alkaline solutions
- Li - 2Li + 2H₂O –> 2LiOH + H₂
- Na - 2Na + 2H₂O –> 2NaOH + H₂
- K - K + 2H₂O –> 2KOH + H₂
What happens when group 1 metals are heated in chlorine gas
- react vigorously - reaction becomes more vigorous down group
- form white metal chloride salts
- Li - LiCl
- Na - NaCl
- K - KCl
What happens when group 1 metals react with oxygen
- react vigorously - reaction becomes more vigorous down group
- form metal oxides
- Li - lithium oxide (Li₂O)
- Na mixture of sodium oxide (Na₂O) + sodium peroxide (Na₂O₂)
- K - mixture of potassium peroxide (K₂O₂) + potassium superoxide (KO₂)
Why do group 1 metals tarnish in air
Metal reacts with oxygen in air to form a dull metal oxide layer
Group 7 elements
Halogens
Halogens
Non-metals with coloured vapours
How are halogens atomically bonded
diatomic - always found in groups of 2 atoms
Fluorine
- yellow gas
- very reactive
- poisonous
Chlorine
- dense green gas
- fairly reactive
- poisonous
Bromine
- red-brown volatile liquid
- dense
- poisonous
Iodine
- dark grey crystalline solid
OR - purple vapour
Group 7 trends
- reactivity decreases down the group
- melting/boiling points increase
- relative atomic masses increase
Why does group 7 reactivity decrease down the group
- more electron shells
- more shielding between nucleus and outer shell electrons
- less attraction between nucleus and outer shell electrons
- harder for atoms to gain an extra electron
What happens when group 7 non-metals form ionic bonds
- gain 1 electron
- gain a charge of 1-
Group 0 elements
Noble gases
Reactivity of group 0 elements
Inert
Inert
Unreactive
Why are noble gases inert
- full outer shell of electrons
- don’t need to lose/gain any
How are noble gases atomically bonded
Monatomic - single atoms not bonded to each other
Group 0 elements at room temperature
Colourless gases
Flammability of group 0 elements
non-flammable
Trends in group 0
- boiling points increase down the group
- relative atomic masses increase down the group
Why do group 0 boiling points increases down the group
- number of electrons in each atom increases so there are greater intermolecular forces between them
- more energy needed to overcome them
