Chapter 7 Periodicity Flashcards
What did Mendeleev do to the elements?
Arranged elements in order of atomic mass
Elements lined up in groups wih similar properties
Elements were swapped around and left gaps
Predicted missing element’s properties
How are elements arranged?
Arranged in 7 horizontal periods and 18 verticle groups
In order of increasing atomic number
Each element in a group has atoms with the same number of outer-shell electrons and similar properties
Elements in the same period have the same number of electron shells
What is ionisation energy?
Measures how easily an atom loses electrons to form positive ions
What is the first ionisation energy?
Energy reqiured to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous +1 ions
How is the first electron lost?
The electron is lost from the highest energy level which experiences the least attraction from the nucleus
What affects the ionisation energy level?
The greater distance between the nucleus and the outer electrons, the less nuclear attraction
The more protons there are in the nucleus, the greater the attraction between the nucleus and the outer electrons
The repulsion in the inner shielding reduces the attraction between the nucleus and outer shell electron
What is the evidence for different electron energy levels?
Successive ionisation energy. Large increase inbetween 2 ionisation energies suggests moving to the next shell, closer to the nucleus and with less shielding
What is the general pattern for first ionisation energy?
A general increase in first ionisation energy across each period.
Sharp decrease between the end of period one and the start of next period.
Nuclear charge increases, similar shielding, nuclear attraction increases, atomic radius decreases
Decreases down the group- nuclear charge outweighed by increased radius and less shielding
Why is there a slight decrease in ionisation energy in group 3 and group 6?
Linked to the filling of subshells
Marks the start of pairing in the next subshell
What are the properties of metals?
All metals except mercury are solid
All able to conduct electricity
High melting and boiling point
Metals don’t dissolve
What is the structure of metals?
Metals are held in giant metallic structure
In solid metals, each atom donates electrons to a shared pool of electrons, which are delocalised from throughout the whole structure
Metallic bonding is the strong electrostatic attraction between cations and delocalised electrons
Cations are fixed, maintaining sturcture and shape
What are the properties of giant covalent lattices?
High melting and boiling points due to strong covalent bonds
Soluble in all solvents
Don’t conduct electricity, except graphene and graphite.
What is the trend of melting points?
Melting point increases from Group 1 to Group 14
There is a sharpy decrease in melting point between Group 14 and Group 15, low melting points from Group 15 to Group 18, marking the decrease in melting point marks the change from giant to simple molecular structure
