Periodic Patterns Flashcards
What is covalent radius
Half the distance between nuclei of atoms that are covalently bonded together
As you go down a group, covalent radius…
Increases
Why does covalent radius increase as you go down a group
- number of electron shells increases
- increased shielding
- electrons further away from nucleus
- atom size increases
As you go across a period, covalent radius…
Decreases
Why does covalent radius decrease as you go across a period
- electrons are gradually filling up energy levels
- more protons
- increased nuclear charge
- electrons pulled in closer and tighter
- atom size decreases
What unit is atomic size measured in
Picometers (pm)
1 x 10^-12 m
What is Van der Waals radius
Half the distance between atoms nuclei that aren’t bonded together
What is the first ionisation energy
The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms
What is the general equation for the first ionisation energy
M (g) ——> M+ (g) + e-
What is the second ionisation energy
The energy required to remove a second mole of electrons
What is the general equation for the second ionisation energy
M+ (g) ——> M 2+(g) + e-
What is the third ionisation energy
The energy required to remove a third mole of electrons
What is the general equation for the third ionisation energy
M 2+(g) ——> M 3+(g) + e-
As you go down a group, ionisation energy…
Decreases
Why does ionisation energy decrease as you go down a group
- number of electron shells increases
- atomic size increases
- outer electrons are further away from nucleus
- increased shielding
- less energy required to remove e-
As you go across a period, ionisation energy…
Increases
Why does ionisation energy increase as you go across a period
- gradually filling up e- shells
- more protons
- nuclear charge increases
- outer e- held tighter and closer to nucleus
- atomic size decreases
- more energy required to remove e-
What is electronegativity
The measure of an atoms attraction for bonding electrons
What does it mean if an atom is said to be highly electronegative
It has a strong attraction for bonding electrons
As you go down a group, electronegativity…
Decreases
Why does electronegativity decrease as you go down a group
- number of e- shells increases
- shielding increases
- outer e- further away from nucleus
- less attraction for bonding e-
As you go across a period, electronegativity…
Increases
Why does electronegativity increase as you go across a period
- more protons
- nuclear charge increases
- covalent radius decreases
- +ve nucleus attracts bonding electrons more strongly
Why does group 8 (noble gases) not have electronegativity values
They have no bonding electrons
What can electronegativities be used for
Predicting the type of bonding that would occur between atoms of 2 elements
How are elements in the periodic table arranged
In order of increasing atomic number
What are groups
Vertical columns within the table containing elements with similar chemical properties resulting from a common number of outer electrons
What are periods
Rows of elements arranged with increasing atomic number, demonstrating an increasing number of outer electrons and a move from metallic to non-metallic characteristics
Which elements form metallic bonds
Li, Be, Na, Mg, Al, K, Ca
Which elements form covalent molecules
H2, N2, O2, F2, Cl2, P4, S8 and fullerenes (e.g. C60)
Which elements form a covalent network
B, C (diamond and graphite), Si
Which elements are monatomic
The noble gases
