Title: Periodic Table Trends
1Periodic Table - Trends
- The Ultimate Cheat-Sheet
- (if you know how to use it)
2Atomic Radii
- We must use an indirect method to measure the
diameter of an atom - The atomic radius is one half of the distance
between the nuclei of two atoms of the same
element when the atoms are joined
3Trends in Atomic Radii
4In general, atomic size increases from top to
bottom within a group and decreases from left to
right across a period.
5Ionization energy
- The energy required to remove an electron from an
atom is called ionization energy - The energy required to remove the first electron
from an atom is called the first ionization
energy, IE1 - The energy to remove successive electrons is
called IE2, IE3, etc.
6Group Trends in Ionization Energy
- State the trends in ionization energy
- Which group has maxima?
- Which group represents minima?
- Account for these trends in terms of electron
configurations
7Group 8 The Noble Gases
- These elements represent maxima because their
outermost energy levels are filled
8Group 1 The Alkali Metals
- These elements represent minima because they all
have one more electron than a noble gas. - This outermost electron starts a new energy level
- lithium 1s2 2s1
- sodium 1s2 2s2 2p6 3s1
- potassium 1s2 2s2 2p6 3s2 3p6 4s1
9Periodic Trends in Ionization Energy
- The first ionization energy of representative
elements tends to increase from left to right
across a period - Nuclear charge increasesfrom left to right but
theshielding effect remainsconstant - So, the attraction of the nucleus for an
electron increases from left to right in a
period
10Trends in Ionization Energy
- First ionization energy tends to decrease from
top to bottom within a group and increase from
left to right across a period
11Ionization Energies for Successive Electrons
Note huge jumps in IE as we try to remove a core
electron - one from a filled lower energy level
12Trends in Ionic Size
- During reactions between metals and nonmetals
- metal atoms tend to lose electrons
- nonmetal atoms tend to gain electrons
- This affects the size of the resulting ions
- Cations are always smaller than the atoms from
which they form - Anions are always larger than the atoms from
which they form
13Examples of Atomic vs. Ionic Size
14Reactivity Within a Group
- Increasing reactivity in Group 1
- Li Na K Rb Cs
- Two reasons
- All tend to lose outer e
- Larger atoms lose this valence electron more
easily. Why? - Valence e is farther from nucleus
15Reactivity Within a Group
- Increasing reactivity in Group 7
- F Cl Br I
- Two reasons
- All tend to gain an e to fill outer level
- Smaller atoms fill outer level more easily. Why?
- Valence electrons are closer to nucleus