Transcript Periodic Table Trends

Periodic Table Trends
Learning Goal
• Students will demonstrate an understanding of periodic trends in the
periodic table
Periodic Table – Day 1
1. Create your Periodic Table.
2. You should have all element symbols, names, atomic numbers and
masses included.
3. Colour your periodic table to match the groups.
*You will use this periodic table for the remainder of the semester. If
you don’t put the information on your table, you wont have it for the
remainder of the semester. This is where it is worth your time to put in
the effort! ***
Periodic Table – Day 2
• Atomic Radius – the estimate of the size of an atom from its nucleus to its outer
perimeter
• Atomic Radius decreases from left to right across the period
• This is because the number of protons in the nucleus increases as you move right across
the PT, as the nuclear charge increases, the outermost electrons are more strongly
attracted to the nucleus, decreasing the distance between the electrons and the nucleus
• Atomic Radius increases as you move down a group
• As you go down a group, the nucleus of each element contains more and more electrons,
which occupy more shells. The outer electrons feel the attractive pull of the protons but
are repelled by the inner electrons making the radii larger
Atomic Radius
Ionization Energy
• Ionization energy – the energy needed to remove an electron (from a
gaseous atom)
• Ionization energy increases as you move across the periodic table (as
the atomic radius decreases)
• The number of charges on the nucleus increases and attracts the bonding pair
of electrons more strongly, more energy is required to remove an electron
• Ionization energy decreases as you move down the periodic table (as
the atomic radius increases)
• The outer electrons become further from the nucleus, making the attraction
weaker, less energy is required to remove an electron
Ionization Energy
• Ionization can happen in stages.
• The first stage of ionization energy is the energy required to remove an
electron, the second stage is the energy required to remove a second electron,
etc.
• Use Aluminium as an example…
Electron Affinity
• Electron Affinity is the energy released when an electron is added (to a gaseous
atom)
• Electron affinity increases as you move from left to right across the periodic
table
• Electron affinity decreases as you move down the periodic table
• A large value of ionization energy indicates that the removal of an electron from
a gaseous atom is difficult and unlikely to occur
• A large value of electron affinity indicates that a lot of energy is released when
an electron is added to a gaseous atom, and is likely to occur
Electron Affinity
Electronegativity
• Electronegativity – the pull from the nucleus
• The most electronegative elements are in the upper right corner of
the periodic table; the least electronegative elements are in the lower
left
• Electronegativity tends to increase from left to right across a period
and decrease down a group
• You need to add the electronegativities of the elements to your
periodic table.
Reactivity
• Reactivity – how vigorously an atom reacts with other substances
• The extremes of electronegativity correlate with chemical reactivity,
the most reactivity chemical elements are those with highest and
lowest electronegativities
• As you move down (and to the left) the left side of the periodic table
the reactivity increases, it’s easier for electrons to be given or taken
away
• As you move across (and up) the right side of the periodic table the
reactivity increases, it’s easier for electrons to be exchanged