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
