Module 3.1.1 - Periodicity (w/ ionisation)
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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