4. Periodicity Flashcards
What is an element called that has some properties of a metal and some of a non-metal?
Metalloids or semi-metals
Where is the step line which separates metals and non-metals?
From the left of Boron to the left of Astatine
Where are semi-metals in the periodic table?
Elements that touch the step line
Give an example of a semi-metal and the properties it exhibits
Silicon
Conducts electricity (not as well as a metal) Shiny
Where is the s-block on the periodic table?
Groups 1 and 2 (and hydrogen and helium)
Where is the p-block on the periodic table?
The right hand side: groups 3,4,5,6,7 and 0 (not helium)
Where is the d-block on the periodic table?
The transition metals block
Where is the f-block on the periodic table?
At the very bottom underneath the d-block
Which two d-block elements are not transition metals?
Zinc and scandium: they do not form compounds which have partly filled d-orbitals- a characteristic of transition metals.
Generally how does reactivity increase in the s-block?
More reactive as we go down the group
Generally how does reactivity increase in the p-block?
More reactive going up the group
How reactive are the transition metals?
They are rather unreactive
How do elements in group 5,6 and 7 bond?
They either accept electrons to form ionic compounds or share their outer electrons to form covalent compounds.
What kind of melting points do giant structures tend to have?
High melting and boiling points
What kind of melting points do molecular structures tend to have?
Low melting and boiling points
Describe the trends in boiling and melting points across period 3
From sodium to aluminium the melting and boiling points increase (increasing number of delocalised electrons)
The melting points of the non metals in period 3 depend on the sizes of their van der Waals forces which depends on how many electrons are in their molecules.
They are therefore ordered: S8 > P4 > Cl2
Silicon with its giant structure has a much higher melting point
What are the trends in atomic radii?
Atoms get larger as we go down a group
Atoms get smaller as we go across a period
Why does the attic radii get smaller across a period?
The nuclear charge increases across a group but the shielding stays the same.
Why does the radii of atoms increase down a group?
Going down a group there is an extra complete main level compared with the one before.
The ionisation energy …. Across a period
The ionisation energy increases across a period.
Why does he ionisation energy increase across a period?
The number of protons in the nucleus increases but the shielding remains the same.
The first ionisation energy….. Down a group
The first ionisation energy decreases down the group
Why does the first ionisation energy decrease as we go down the group?
The outer electron is further away from the nucleus and there is an increase in shielding.
What is the trend in ionisation energy from one period to the next? (From period 0 to period 1)
There is a decrease in ionisation energy because there is increased shielding and he outermost electron is further from the nucleus. Hence, the electron is easier to remove.
What are the exceptions to the increasing ionisation energies across period 3?
Magnesium to aluminium (decreases due to moving up from 3s to 3p)
Phosphorus to sulfur (decreases due to the electron repulsion in one of the 3p orbitals)
What is the trend in successive ionisation energies?
The ionisation energy increases because it gets harder to remove the next electron. They increase more significantly when you remove an electron from the next main energy level down.
