Module 3.1.1 - Periodicity (w/ ionisation) Flashcards
What does the periodic table show?
Patterns of chemical and physical properties
What are horizontal rows of elements called?
periods
What are vertical columns of elements called?
groups
How is the periodic table arranged?
Increasing atomic number (increasing number of protons in the nucleus)
What do elements arranged in periods show?
Trends in physical and chemical properties across a period that are repeated across each period
What is periodicity?
The repeating pattern of trend across different periods
What do elements in the same group show?
- Have similar chemical and physical properties
- their atoms have the same number of outer shell electrons
What are metalloids also known as?
semi-metals
Why do elements in the same group react in a similar way?
They have the same outer shell electron configuration
What do chemical reactions involve?
Only involve electrons in the outer shell
What do elements in the same period have?
A common core of electrons
What are s-block elements?
Have their highest energy outer shell electron in an s-orbital
What happens to atomic radii across a period?
Atomic radii decreases from left to right
- Protons added to nucleus: nuclear charge increases
- Electrons added to the same shell
- Nuclear attraction on outer shell electrons increases across a period
- Electron shells are drawn inwards by the nucleus,making atoms smaller
What happens to atomic radii down a group?
The atomic radii increases down a group
- The number of shells increase
- Outer electron added to a new shell which is further away from the nucleus
- Shielding effect by inner shell electrons increases down a group
- Increased distance of outermost electron from nucleus and shielding effect far outweigh the increase in nuclear charge
- Nuclear attraction decreases down a group
What does the period number tell?
The number of shells the atom has
What does the group number tell?
The number of outer shell electrons
What happens across a period in terms of melting and boiling points?
- Increase gradually from group 1 to group 4
- Decrease sharply between group 4 and 5 (signifies a change in structure from giant to simple)
- are comparatively low from group 5 to group 8
Why do groups 1-4 have a high melting and boiling point?
- Have a giant structure
- The bonds that need to be broken are strong bonds between atoms/particles
Why do groups 5-8 have comparatively low melting and boiling points?
- Have a simple structure
- Bonds that need to be broken are weak intermolecular bonds between molecules
What does the process of ionisation produce?
Ions with a positive charge
- electron is moved from the outer shell
What is first ionisation energy?
The energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions
Why is the outer most electron removed first in ionisation?
The electron experiences the least nuclear attraction
What factors affect ionisation?
- Nuclear charge
- Distance of outermost electron from the nucleus
- Electron shielding
How does nuclear charge affect ionisation energy?
- More protons, the greater its nuclear charge
- Stronger the nuclear attraction on outer electrons
- Higher nuclear charge requires more energy to overcome attraction between nucleus and outermost electron
How does distance affect ionisation energy?
- as distance between the nucleus and outermost electron increases, the attraction between them decreases
- the weaker the nuclear attraction, less energy is needed to remove the outer electron
How does electron shielding affect ionisation energy?
- electron shielding; the repulsion between electrons in inner shells
- reduces the net nuclear attraction from positive nucleus on outer shell electrons
- more shells, the greater the shielding effect and weaker the nuclear attraction
What is the general trend down a group for 1st ionisation energy?
- First ionisation energy decreases
- more shells, more shielding effect from inner shell electrons
- atomic radius increases
- increased distance from nucleus and increase shielding effect far outweigh increase in nuclear charge
- nuclear attraction hence decreases on outer shell electrons
- less energy is needed to remove the outer electron
What is the general trend across a period for first ionisation energy?
- first ionisation energy shows a general increase across a period
- the outer electron fills the same shell, shielding remains the same
- the number of protons increases, nuclear charge increases
- atomic radius decreases
- hence a greater nuclear attraction on outer electrons
- more energy needed to remove outer electron
Where does ionisation energy across a period show a decreases
- group 2 and 3
- group 5 and 6
Why is there a decrease in IE between group 2 and 3?
- the p sub-shell (group 3) has higher energy than s sub-shell (group 2)
- the p electron needs less energy to be removed, giving it a lower 1st IE
Why is there a decrease in IE between group 5 and group 6?
- there is an electron pairing in the p orbital in group 6 element
- in the group 5 element, each p orbital contains one electron: one p orbital in group 6 element contains two electrons paired
- the paired electrons repel each other, it is easier to remove one of these electrons
- hence less energy needed
What is successive ionisation energy?
A measure of the energy required to remove each electron in turn
What does a successive ionisation energy graph show?
- shows the largest increase in ionisation energy; the electron has been removed from a new shell that is closer to the nucleus and has less shielding from inner electrons
- shows how many electrons in outer shell; what group the element is in
Why does successive ionisation energy increase with ionisation number?
- once an electron has been removed, there are the same number of protons but fewer electrons
- proton:electron ratio increases
- remaining electrons more strongly attracted to nucleus; more energy is needed to remove each electron in turn
