Periodicity Flashcards
How are the elements arranged in a periodic table?
In order of increasing atomic numbers
What is meant by periodicity?
The repeating trends in chemical and physical properties
What change happens across each period?
Elements change from metals to non metals
How can the electron configuration be written in short?
The noble gas before the element
E.g Li —> 1s2 2s2 ; Li —> [He] 2s1
Define the first ionisation energy
The energy required to remove one electron from each atom in one mole of the gaseous element to form one mole of gaseous 1+ ions
What is the 1st ionisation energy of magnesium?
Mg (g) —> Mg+ (g) + e-
What are the factors that affect Ionisation energy?
Atomic radius
Nuclear charge
Electron shielding or screening
Why does the 1st IE increase across period 3?
Increased nuclear charge
Decreased atomic radius
Same electron shielding
This means more energy is needed to move the 1st electron
IE decreases at Al- outer electron is in 30 orbital (higher than 32 orbital) so less energy needed to remove
Decreases at S because a 3p orbital has 2 electrons (electron repulsion)
Why does the 1st IE decreases between group 2 & 3?
In group 3 the outermost electron are in p orbitals where as in group 2 they are in s orbital
Electrons are more easily removed
Why does 1st IE decreases between group 5 & 6?
The decrease between 5 and 6 is due to the group 5 electrons in p orbital are single electrons but in group 6 the outermost electrons are pared and electron repulsion occurs
So electrons are slightly easier to remove
Does 1st IE increase or decrease between the end of one period and the start of the next?
Decrease
There is an increase in atomic radius - electrons are further away from the nucleus
Increase in electron shielding- weaker atteaction so electrons are removed easier
Does 1st IE increase or decrease down a group?
Decrease
Shielding increases - weaker attraction
Atomic radius increases - distance between the outer electrons and nucleus increases - weaker attraction
Increase in nuclear charge is outweighed by increase in distance and shielding
What are the properties of giant metallic lattices
High melting and boiling point
Good electrical conductors
Malleable
Ductile
What is a ductile metal?
The metal can be drawn into a wire
What is a malleable metal?
The metal can be shaped into different forms
Describe the structure, forces and bonding in every element across period 2
Li & Be (metallic bonding) — giant metallic ; strong attraction between positive ions and delocalised electrons
B & C (covalent) — giant covalent ; strong forces between atoms
N2, O2, F2, Ne — simple molecular ; weaker intermolecular forces between molecules ; covalent bonding within molecules
Describe the structure, forces and bonding in every element across period 3
Na, Mg, Al (metallic bonding) — giant metallic ; strong attraction between positive ions and delocalised electrons
Si (covalent) — giant covalent; strong forces between atoms
P4, S8, Cl2, Ar — simple molecular; weak intermolecular forces between molecules; covalent bonding within molecules
