4.1.2 Atomic structure and the Periodic Table (must know) PAPER 1 Flashcards
Trends of group 7 (halogens)
As you go down the list: Less reactive (harder to gain an extra electron as the outer shells further from the nucleus) Higher melting and boiling points Higher relative atomic masses
Why do group 7 react in similar ways
They all have 7 electrons in their outer shell
How were elements first arranged in early 1800s before the discovery of protons, neutrons and electrons
By atomic mass
What did Dmitri Mendeleev do to the periodic table (1869)
He left gaps for elements he predicted would be discovered
He switched elements around if their properties were like those of elements in other groups, changed the order based on atomic mass
Why didn’t scientists agree with Dalton and Newlands table (early periodic table)
Some boxes had 2 elements
Unreactive Cu and Ag in same group as very reactive Li, Na and K
No gaps left for undiscovered elements
Why didn’t scientists agree with mendeleevs table
Some boxes still had 2 elements
Unreactive Cu and Ag in same group as very reactive Li, Na and K
What do the periods tell us in the periodic table
How many electron shells it has
What does the group number tell us in the periodic table
How many electrons there are in its outer shell
Why do metals lose electrons to form ions
They dont have many electrons to remove from their outer shell and some metals have outer electrons far away from the nucleus so weak attraction
Not much energy is needed to remove the electrons from the outer shell
What happens to do with halogens and displacement
A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt
How do halogens react with non metals
They share electrons via covalent bonding to achieve a full outer shell for example HCl or CCl4
How do halogens react with metals
They have 7 electrons in their outer shell so they gain one to fill the outer shell
When they gain an extra electron they become 1- electrons (known as halide ions)
Eg when chlorine gains an atom it becomes Cl-
An example displacement reaction with chlorine and bromine
using potassium
Chlorine is more reactive than bromine so chlorine will displace bromine from an aqueous solution of its salt (a bromide)
Chlorine + Potassium bromide –> Bromine + Potassium chloride
Cl2 + 2KBr –> Br2 + 2KCl
Why is there no reaction between a halogen and a halogens salt
(bromine + chloride salt)
Nothing would happen as chlorine is more reactive than bromine so the bromine cannot displace the chlorine from the chloride salt
What happens as you go down group 1 (alkali metals)
The reactivity increases
Melting point decreases
Boiling point decreases
Why does the reactivity increase as you go down group 1
The outer electron gets further away from the nucleus so the attraction between the outer electron and the nucleus decreases, so the outer electron is more easily lost
What happens when group 1 react with non-metals
They form ionic compounds
Group 1 have 1 electron in their outer shell so its easy for them to lose it to form a 1+ ion
What is the basic equation for when group 1 reacts with water
Alkali metal + Water –> Metal hydroxide + Hydrogen
Sodium reacts with water to form ? (group 1 equation)
Write out the full equation
2Na + 2H2O –> 2NaOH + H2
What happens when group 1 react with chlorine and whats the general equation
They react vigorously when heated in chlorine gas to form white metal chloride salts
Alkali metal + Chlorine –> Metal Chloride
Equation for when lithium reacts with chlorine (group 1)
2Li + Cl2 –> 2LiCl
What happens when group 1 react with oxygen
They react with oxygen to form a metal oxide
Equation of lithium reacting with oxygen (group 1)
4Li + O2 –> 2Li2O
Properties of group 0 elements
They all have a full outer shell of electrons
Their outer shell is energetically stable so they don’t need to gain or lose electrons
They are inert
At room temp they are colourless single atom gases
What does inert mean
Unreactive
What are the trends as you go down group 0 and why
The boiling points increase as the atomic number increases so the number of electrons increases
This causes intermolecular forces between the atom to increase so more energy is needed to break them and so the boiling point increases
How are elements in the periodic table arranged and why is it called the periodic table
The elements in the periodic table are arranged in order of atomic number and so that elements with similar properties are in columns, known as groups.
The table is called a periodic table because similar properties occur at regular intervals
How were Mendeleevs ideas accepted
Elements with properties predicted by Mendeleev were discovered and filled the gaps
Strong support for a scientific idea can be found if predictions from that theory are found to be true by experiment
Why are metals on the left and lose electrons
They have few electrons on their outershells and as you go down the periodic table the force of attraction becomes weaker as the outer shell is further from the nucleus
Not much energy is needed to remove the outer electrons so this means it’s easier to lose electrons
Why are non metals on the right and gain electrons
They have lots of electrons on their outershell and tend to be near the top of the periodic table so the outershell electrons have a strong force of attraction so little energy is needed for electrons to be gained
