C1 Atomic Structure and the Periodic Table Flashcards
How many elements are there
There are 118 different types of elements that humans have discovered and each one has its own chemical symbol
What are atoms
Atoms are the smallest possible unit of an element
What are compounds
Molecules made up of the atoms of at least 2 different elements
Compounds have formulae that are made by combining the chemical symbols of the elements that combine to make them
What happens in a chemical reaction
Compounds are broken up or formed
New substances are created
Energy change
No atoms are created or destroyed
What is a chemical equation
A written representation of a chemical reaction
What are reactants
Chemicals that are reacting with each other are called the reactants
Reactants are found on the left of equations
What are products
Chemicals that are being made are called the products
Products are found on the right of equations
What is a word equation
A chemical reaction expressed in words rather than chemical formulae
Word equations state the reactants, products, and direction of the reaction in a form that could be used to write a chemical equation
What is a symbol equation
A symbolic representation of a chemical reaction
Symbol equations state the reactants, products, and direction of the reaction
Symbol equations must be balanced
What are mixtures
Mixtures are made of 2+ substances (elements or compounds) that haven’t been combined chemically
Mixtures can be separated
Their chemical properties don’t change because they have been mixed with another substance
What are separation techniques
A physical process used to separate mixtures and compounds into the elements or compounds that make them up
What is crystallisation
A separation technique for separating solutions into solutes and solvents
What is filtration
A separation technique for separating mixtures that contain insoluble solids and liquids
Performed by passing the mixture through filtration paper
The insoluble solid is trapped by the filter paper
The liquid runs through the filter paper and is collected
What is chromatography
A separation technique for separating multiple solutes from a solvent
What is distillation
A separation technique used to separate a mixture of liquids
Uses the liquids’ different boiling points to separate them
What is simple distillation
A separation technique for separate two liquids with different boiling points
What is fractional distillation
A separation technique used to separate multiple liquids with different boiling points
What is Dalton’s model of the atom
John Dalton proposed an atomic model often referred to as the Billiard Ball Model
He defined an atom to be a ball-like structure, as the concepts of atomic nucleus and electrons were unknown at the time
What is Thomson’s model of the atom
English physicist called J. J. Thomson discovered electrons
Thomson modelled the atom as a ‘plum pudding’: a ball of positive charge (dough), with negatively charged electrons (currants in the pudding) mixed in with the ‘dough’
What is Rutherford’s model of the atom
Ernest Rutherford discovered that alpha particles could bounce back off atoms
Rutherford concluded that an atom’s mass is concentrated in the atom’s centre.
This was called the “nucleus” and it contained positively charged particles called protons
Referred to as the nuclear model
What is Bohr’s model of the atom
Niels Bohr discovered that electrons orbit the nucleus at fixed distances
What is the relative charge of a proton
+1
What is the relative charge of electrons
-1
What is the relative charge of neutrons
0
How is relative mass calculated
Number of protons + number of neutrons
What size are atoms
The radius of an atom is approximately 0.1 nanometres
The nucleus of an atom is 10,000 times smaller than the atom
What are isotopes
Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number
All isotopes of a given element have the same number of protons but different numbers of neutrons in each atom
What is protium
Protium is a hydrogen atom with 1 proton and no neutrons
99.98% of hydrogen atoms are protium
Used in fuel cells and the production of plastic
What is deuterium
Deuterium is a hydrogen atom with 1 proton and 1 neutron
0.02% of hydrogen atoms are deuterium
Used in nuclear fusion
What is tritium
Tritium is a hydrogen atom with 1 proton and 2 neutrons
Very rare
Used in thermonuclear fusion weapons
What is relative atomic mass
Average mass of all the isotopes of an element
Takes into account isotope abundance
What is electron structure
Electrons have fixed positions in atoms called shells or energy levels
Shells go around the atom’s nucleus
What are electron shells
Electrons fill an atom’s shells in order of increasing energy
The closer a shell is to the nucleus, the lower its energy level, so the first shell that is filled is the closest to the nucleus
What is electron configuration
Electron configuration tells us how an atom’s electrons are organised
The inner shell can have a maximum of 2 electrons and the next two shells can have a maximum of 8 electrons
Extra electrons are then put into a fourth shell and so on
What is the periodic table
The periodic table is an ordered arrangement of all 118 known elements
The elements are arranged in order of their atomic number
Every time you move an element to the right, the proton number increases by 1
What are periods
Rows of the periodic table
The table is periodic because element with similar properties are found at regular intervals
What are groups
Columns in the periodic table are known as groups
Elements in the same column have the same number of valence electrons
Group number is the number of valence electrons an element has
How are chemical properties predicted using the periodic table
Because all elements in a group have the same number of valence electrons, they have similar chemical properties
What is Newland’s table of elements
John Newlands was the first chemist to devise a periodic table
Newlands’ periodic table was ordered by the mass of the element
The table was incomplete, and some elements were placed in inappropriate groups
What is Mendeleev’s table
Dmitri Mendeleev recognised that there may be undiscovered elements
Mendeleev added gaps to Newlands’ table to account for undiscovered elements.
Mendeleev even predicted the properties and masses of these undiscovered elements
What did Henry Moseley discover
Protons
Isotopes
What are metals
Elements found on the left of the periodic table because they have few valence electrons
When metals react, they lose their valence electrons to become cations
What are the properties of metals
High melting and boiling points
Good conductors of heat and electricity
Solid at room temperature (except mercury)
What are non-metals
Found on the right of the periodic table as they have many valence electrons
When non-metals react they gain electrons to become anions or share electrons to form neutral molecules
What are the properties of non-metals
Low melting and boiling points
Often gaseous
Generally do not conduct heat or electricity
What are alkali metals
Found in group 1 of the periodic table
Have 1 valence electron
What are the properties of lithium
Electron structure (2,1)
Least reactive of the alkali metals
Burns with a crimson flame when it reacts with oxygen
Floats on the surface of water and will release bubbles of hydrogen gas (it effervesces)
What are the properties of sodium
Electron structure (2,8,1)
More reactive than lithium because its outer electron is less strongly attracted to the positively charged nucleus; this is due to a greater distance from the positive charge of the atom’s nucleus
Floats on the surface of water, which releases enough heat to melt the sodium
Moves quickly across the surface of the water
Burns with a yellow/orange flame when it reacts with oxygen
What are the properties of potassium
Electron structure (2,8,8,1)
More reactive than lithium and sodium because its outer electron is least strongly attracted to the nucleus
Floats on the surface of water, and has a similar, but more vigorous, reaction compared with sodium
Burns with a lilac flame when it reacts with oxygen
What are the properties of group 1 metals
Very reactive as they only have one valence electron
Low melting points
Reactivity increases down the group
What happens in a reaction between alkali metals + chlorine
A metal chloride is formed, which dissolves in water to give a colourless solution
What happens in a reaction between alkali metals + oxygen
Rapidly turns from silvery shiny to dull as a metal oxide is produced
What happens in a reaction between alkali metals + water
The metal reacts to create a metal hydroxide
This floats on the water
Energy released from the reaction is enough to melt the metal
What are transition metals
Found in the middle of the periodic table
In between groups 2 and 3
How reactive are transitional metals in comparison to alkali metals
Less reactive
E.g. Iron takes weeks to rust when in contact with oxygen and water, whereas sodium does this in a few seconds
What are the melting points of transitional metals in comparison to alkali metals
Higher melting points
High melting points make transition metals useful for cooking equipment
E.g. Iron’s melting point is 1,583°C, whereas sodium’s is about 98°C
What are the densities of transitional metals in comparison to alkali metals
Denser
High density makes transition metals useful in construction
Strength and hardness of transition metals in comparison to alkali metals
Stronger and harder
What ions can transition metals form
Cations with different charges
E.g. Fe2+, Fe3+
Cu+, Cu2+
What is the colouration of transition metal compounds like
Can form different coloured compounds
E.g. Cu(I)So4 is white
Cu(II)So4 is blue
Can transition metal be used as catalysts
Can be used as catalysts
E.g. Fe (Harber process)
Pt & amp; Rh (Catalytic converters)
What are noble gases
An element found in group 0
Their other shell is full
What is the reactivity of noble gases like
Elements in Group 0 are nonreactive because they have a full outer electron shell.
They do not gain or lose electrons to fill up this shell as it is already full
Used in light bulbs because they will not react with the hot metal filament
What are atoms of noble gases like
Because noble gases are unreactive, they exist as single atoms instead of forming molecules
What are the boiling points in noble gases and what trend do they follow
Low boiling points
Boiling points do increase as you move down the periodic table
This is because the relative atomic mass increases lower down the periodic table
What are the densities of noble gases
Low densities
Their densities increase as you move down the periodic table because of their increasing relative atomic mass
What are halogens
An element found in group 7
Their outer shell has 7 electrons
What are halogens like in their elemental form
In their elemental form, halogens share electrons to make diatomic molecules
What are salts
When a metal atom transfers its outer electron to a non-metal atom (like a group 7 atom), salts are formed
The result is a compound where all the ions have a full outer shell
What trend does halogen reactivity follow
As you move down the group, the halogens decrease in reactivity. This is because:
The atoms gain more electron shells.
So, the distance between the outer electron shell and the nucleus increases.
So, the attraction between the nucleus and the electron (to be gained from another element) decreases.
What happens, in terms of valence electrons, when halogens react
They gain one electron to fill their outer shell
This forms an anion
What did James Chadwick discover
Some particles in the nucleus have no charge at all
He called them neutrons
When did James Chadwick make his discovery
1932
How is crystallisation performed
Heating a mixture to evaporate the solvent
Evaporation leaves behind crystals of the solute
The solvent is collected through condensation
How is chromatography performed
Performed by placing a drop of the solution to be separated near the bottom of a piece of chromatography paper
The paper is dipped into a suitable solvent. The solvent moves up the paper and carries the solutes in the solution
Different solutes move at different speeds, so they separate on the paper
How is simple distillation performed
Performed by heating the mixture until the liquid with the lower boiling point starts to boil
Vapour released is passed through a condenser, where the gas cools back into a liquid
Simple distillation can also separate a solute from a solvent when the solvent has a lower boiling point than the solute
How is fractional distillation performed
Performed by heating the mixture until the liquid with the lowest boiling point boils and then condenses
Temperature is then increased to collect the other fractions
When did John Dalton propose him atomic model
1803
When did JJ Thompson propose him atomic model
1897
When did Ernest Rutherford propose him atomic model
1909
Where are protons found
The nucleus
Where are electrons found
In fixed orbits around the nucleus
Where are neutrons found
The nucleus
How is relative atomic mass calculated
the sum of the masses of an element’s isotopes, each multiplied by its natural abundance
What did Henry Mosley’s discoveries show
Henry Mosley’s discoveries showed that Mendeleev table worked as the element had been ordered by atomic mass
