3.1.1 - Periodicity Flashcards
What is periodicity ?
Its the term that refers to periodic table as the arrangement of elements in periods showing repeating trends in physical and chemical properties.
How does the periodic table arrange elements ?
- In periods By increasing atomic (proton) number.
- In groups showing similar in chemical and physical properties.
Historical info about periodic table
- Elements were grouped according to their physical properties.
- Elements were grouped in to triads.
How did mendeleev aarrange the peropdic table
- He ordered elements by mass
- Left gaps
- Elements were grouped in terms of similar chemical properties.
How is mendeleeve periodic table different from our table
- Elements are ordered by proton numbers not by mass**.
How are periods ordered ?
In rows
How are groups ordered ?
In colomouns
How are groups and periods different ?
- Elements in the same group have same number of electrons in outer shell.
- Elements in the same period have the same number of electron shells.
- Elements in the same period have the similar properties whereas in periods they do not.
Explain what happens across a period in terms of atomic radius.
- Outer electron are in same shell.
- same amount of shielding
- More protons are in the nucleus.
- So stronger attraction between nucleus and outer shell electrons
- So outer shell electrons are pulled closer to the nucleus.
- making the atom smaller
- Atomic radius decrease
- This reason explains why electronegativity increase across a period.
why does electronegativity increase across a period.
Electronegativity increases because the atoms become smaller, and their ability to attract electrons increases due to the stronger nuclear pull.
note period is not the same as group.
Atomic radius across period graph
What three points do you always need to include when talking about ionisation.
- Atomic radius
- Nuclear charge
- Sheilng.
Explain what you know about shielding.
- More electron shells = more shielding.
- This causes a weaker attraction between the electron that is being removed and the nucleus.
Explain nuclear charge
Explain atomic size
Why does is aluminiums ionisation lower than magnesium ?
Its outer electron sits in 3p which is a lower energy sub shell in contrast to magnesium which has an electron in the 3s shell which has a higher energy.
Evidence for atoms having sub-shells.
Why is sulfurs ionisation lower than phosphorus
- S and P have electrons in 3p orbital so shielding is the same but one of sulfurs orbital has 2 electrons in it whereas p has only one in each orbital.
Evidence for electron repulsion.
Name giant covalent structures
- Graphite, diamond, silicon and graphene
Name all the properties of graphite.
Name all the properties of diamond.
Note to self : Silicon has the same properties as well.
Name all the properties of graphene.
What type of bonding do metals have and give components of this bonding .
Metallic bonding.
- Positive ions and a sea of delocalised electrons
- High melting and boiling points due to strong electrostatic attractions between cations and delocalised electrons
- Can conduct in when solid and in molten as their electrons are free to move and can carry current.
Melting point of phosphorus compared to sulfur
Both simple molecular
Blurt everything you know about chlorine melting point and structure
- Smaller atomic radius too
Why do ionisation energies increase as we remove and from an atom
