topic 3- periodicity Flashcards
what does a periodic table consist of?
groups (vertical columns) and periods (horizontal rows)
how is the periodic table organised?
by order of increasing atomic number
elements in the same group…
have the same number of valence electrons
elements in the same period…
have the same number of electron shells
location of metals
right side
location of non-metals
left side
location of metalloids
border between metals and non metals
what are metalloids (give egs)
chemical elements whose physical and chemical properties fall in between the metal and non-metal categories (boron, germanium, silicon)
alkali metals
group 1
halogens
group 17
noble gases
group 18
groups 3-12
transition metals
top row of ‘island’ at bottom
lanthanides
bottom row of ‘island’ at bottom
actinides
first 2 blocks
outer electron is in s shell
middle block
outer electron is in d shell
far right block
outer electron in p shell
bottom block
outer electron in f block
period number (n)=
outer energy level occupied by electrons
as you go down a group, atomic radius…
increases:
- more shells (increased shielding/distance)
- increase in nuclear charge outweighed
as you go across a period, atomic radius…
decreases:
- shielding stays the same; nuclear charge increases
- outer electrons experience stronger attraction to the nucleus
define ionic radius
the distance between the nucleus of an ion and the outermost shell of the ion.
as you go down a group, ionic radius…
increases:
- there is an extra complete inner shell of electrons
as you go across a period, ionic radius…
decreases:
- nuclear charge increases
- electrons feel a stronger attraction to the nucleus
define ionisation energy
The minimum energy required to remove one electron from each atom in a mole of gaseous atoms.
as you go down a group, ionisation energy…
decreases:
- shielding and distance increase
- this outweighs the increase in nuclear charge
as you go across a period, ionisation energy…
increases:
- all electrons are in the same shell
- nuclear charge increases
define electronegativity
a measure of the tendency of an atom to attract a bonding pair of electrons
as you go down a group, electronegativity…
decreases:
- shielding and distance increase
- electrons experience less attraction to the nucleus
as you go across a period, electronegativity…
increases:
- increased nuclear charge
- shielding is almost the same
define electron affinity
the enthalpy change when one mole of gaseous atoms gain an electron each, forming negative ions
as you go down a group, electron affinity…
decreases:
- nuclear charge decreases
- as a result, it becomes more difficult to add an electron - resulting in a decrease in the amount of energy released.
as you go across a period, electron affinity
increases:
- atomic radius gets smaller
- nuclear charge gets larger.
what are the similarities in the electron configurations of the alkali metals?
they all have 1 electron in their valence shell