3.1 key concepts Flashcards
In a periodic table where can you find s block elements?
Groups 1 and 2
In a periodic table where can you find p block elements?
From groups 3 to 8
In a periodic table where can you find d block elements?
In the area cluster with transition metals (the gap from group 2 and group 3)
In a periodic table where can you find f block elements? (NOT REQUIRED)
Actinides and Lanthanides
What is meant by periodicity?
Trend that occur (in physical and chemical properties) and you move across the periods of the periodic table
How are elements arranged in the periodic table?
Elements are arranged using increasing atomic number (number of protons) from LEFT to RIGHT
What is meant by atomic radius?
The distance of the outermost electron from the nucleus
What is the trend in atomic radius and why?
Atomic radius decreases across the period and increases down the group.
It decreases across the period because the electrons across the period are pulled closer together
It increases down the group because the electrons are in a different energy level. This is because as you have more electrons, more shells are needed
What is meant by electronegativity?
The ability of an atom to attract a pair of electrons in a covalent bond
What is the trend with electronegativity and why??
Electronegativity decreases down a group
Electronegativity increases across a period
As you go down, there are more shells, so there is more shielding meaning that it is harder for the atom to attract electrons
What is meant by melting point/boiling point?
A measure of the energy required to separate the particles in a substance
What is the trend with melting point/boiling point and why?
Metals - High melting point. Increases across the period due to the increasing number of metallic bonding between the positively charged metal ions (cations) and the delocalised electrons
Non-metals - High melting point as it has a giant molecular structure like diamond. A lot of energy is needed to break the covalent bonds holding the atoms together
Give a description of metallic bonding
- Sea of delocalised, free moving electrons
- Giant lattice of positive ions
- Strong electrostatic attractions between the positive ions and the delocalised electrons
What are the properties of metallic bonding?
1) High melting point. - Increases across the period due to the increasing number of metallic bonding between the positively charged metal ions (cations) and the delocalised electrons
2) Malleable - can be hammered into shape
3) Can conduct electricity due to the delocalised electrons
Describe the trend of metallic bonding ranging from group 1 to group 3
Group 1 - Weakest level of metallic bonding
Group 2 - In the middle
Group 3 - Strongest type of metallic bonding
NOTE: Just because it is the weakness type of metallic bonding, it doesn’t mean metallic bonding is weak. Metallic bonding is very strong, but it strength depends on the charge (+1,+2 or +3 ) of the ion formed
What is meant by covalent bonding?
The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
What are the properties of covalent bonding?
Low melting/boiling point due to the weak intermolecular forces between atoms that require little energy to break
Cannot conduct electricity as there are no delocalised electrons
Only soluble in NON-POLAR solvents (remember like dissolves like)
What is the trend with ionisation energy and why?
Ionisation energy decreases down the group
Ionisation energy increases across the period
Decreases down the group - This is because as we go down the group, atomic radius increases. This means that the outermost electron is further away from the the nucleus. This increase shielding (the repulsion of outer electrons by inner electrons) As shielding increases it means that the outermost electron is less attracted to the nucleus so it can be easily lost.
Increases across the period - This is because across the period both atomic radius and shielding decreases meaning that the outermost electron is now closer to the nucleus allowing it to form a strong attraction with it. This means it will now more energy for the element to ionised.
What does the value of ionisation energy depend on?
- Atomic radius
- Size of nuclear charge (How positive the atom or ion is)
- Shielding (the repulsion of outer shell electrons by inner shell electrons)
How do you represent ionisation energy?
M(g) → M+(g) + e-
NOTE : M = Metal (g) = Gaseous (Gas state)
e- = Electron M+ = Metal ion
Give the ionisation energy of Potassium (Group 1)
K(g) → K+(g) + e-
Give the ionisation energy of Magnesium (Group 2)
Mg+(g) → Mg2+(g) + e-
NOTE : Mg+ = Metal ion [first ionisation energy]
(g) = Gaseous (Gas state) e- = Electron
Mg2+ = Metal ion [second ionisation energy]
Give the ionisation energy of Aluminium (Group 3)
Al2+(g) → Al3+(g) + e-
NOTE : Al2+ = Metal ion [second ionisation energy]
(g) = Gaseous (Gas state) e- = Electron
Al3+ = Metal ion [third ionisation energy]
Are successive ionisation energies higher or lower than the previous one , and why?
Successive ionisation energies are always greater than the previous one
This is because the electron is being pulled away from a more positive species
