2.1 Periodicity Flashcards
In what order are elements arranged in the periodic table
Increasing atomic number
Period
Row of elements
Group
Column or elements
Periodicity
The study of repeating trends and patterns in the periodic table
Trend in first ionisation energy across a period
Increases across the period with a dip between group 2 and 3 and between group 5 and 6
First ionisation energy
The energy needed to remove one electron from each atom in one mole of gaseous atoms
Why does first ionisation energy increase across a period
- nuclear charge increases
- similar shielding
- nuclear attraction on outer electron increases
Why does atomic radius decrease across the period
- nuclear charge increases
- same shielding
- attraction on outer electron increases
What are cations like in size relative to their atoms
Smaller
Why are cations smaller than their atoms
Lose electrons and so lose a shell
Same protons attracting fewer electrons
What are anions like in size relative to their atoms
Larger
Why are anions larger than their atoms
Gain electrons so same number of protons attracting more electrons
Electronegativity
The power of an atom to attract the pair of electrons in a covalent bond
What is the trend in electronegativity across a period
Increase
Why does electronegativity increase across a period
Number of protons increase
Electrons in same shell- similar shielding
Attraction on outer electrons increases
Why is there variation in melting and boiling points across a period
Changes in structure and bonding
What is the structure in Na, Mg and Al
Giant lattice
What bonding Na, Mg and Al
Metallic
Trend in boiling and melting points from Na to Al
Increase
Why do melting and boiling points increase from Na to Al
Metallic bonds increase
Charge increases
More delocalised electrons
Attraction between ions and delocalised electrons increases
structure and bonding of silicon
giant covalent
melting and boiling point of Si
v high
why does Si have high m and b point
huge numbers of strong covalent bonds needed to be broken
structure of phosphorus, sulphur and chlorine
simple covalent
melting/boiling points of sulphur, phosphorus and chlorine
relatively low
why are melting/boiling points relatively low in phosphorus, sulphur and chlorine
weak VDW forces between molecules need to be overcome
in what order to boiling/melting points increase in sulphur, phosphorous and chlorine
chlorine>phosphorus>sulphur
why do boiling points increase from chlorine>phosphorus>sulfur
molecules get larger so more electrons involved in bonding- VDWs greater
structure of Ar
atoms
melting/boiling point Ar
very low MP/BP
why does argon have a low melting/boiling point
monoatomic- very weak VDWs between atoms
