This is a short presentation on the trends found in the periodic table.
- 1. Objectives
- Define atomicandionic radii, ionization energy, electron
- Comparethe periodic trends of atomic radii, ionization energy,
and electronegativity, and state the reasons for these
- Define valence electrons,and state how many are present in
atoms of each main-group element.
Section 2Periodic Trends 2. Atomic Radii
- The boundaries of an atom are fuzzy, and an atoms radius can
vary under different conditions.
- To compare different atomic radii, they must be measured under
- Atomic radius - one-half the distance between the nuclei of
identical atoms that are bonded together.
Section 2Periodic Trends 3. Atomic Radii Section 2Periodic
Trends 4. Atomic Radii
- Atoms tend to be smaller as you go from left to right on the
- This is due to increasing positive charge in the nucleus,
pulling the electrons closer to the center.
- Atoms tend to be larger down a group.
- This trend is due to the increasing size of the electron cloud
as electrons fill up larger energy levels.
Section 2Periodic Trends 5. Atomic Radii Section 2Periodic
Trends 6. Ion definition Section 2Periodic Trends
- Watch the video on entitled Ion definition found in this
section of the course
7. Ionic Radii trends Section 2Periodic Trends 8. Ionic Radii
trends Section 2Periodic Trends
- Positive ions tend to be smaller than neutral atoms.
- The larger the positive charge, the smaller the ion.
- Again, this is due to increasing positive charge in the
nucleus, pulling the electrons closer to the center.
9. Ionic Radii trends Section 2Periodic Trends
- Negative ions tend to be larger than neutral atoms.
- The more negative the charge, the larger the ion.
- This is due to the repelling forces between electrons, causing
them to occupy a larger space around the atom
10. Ionization Energy Section 2Periodic Trends
- The process to form an ion is called ionization.
- The energy required to remove one electron from a neutral atom
is calledionization energy .
- Sometimes refered to asIE 1 orfirst ionization energy .
11. Ionization Energy Section 2Periodic Trends
- Ionization energies increase across a period.
- Caused by increasing effect nuclear charge
- Higher positive charge more strongly attracts electrons in the
same energy level
12. Ionization Energy Section 2Periodic Trends
- Ionization energies decrease down a group.
- Electrons removed from larger atoms are at higher energy
levels, and are farther away from the nucleus.
- Electrons are removed more easily due to their distance from
13. Ionization Energy Section 2Periodic Trends 14. Ionization
Energy Section 2Periodic Trends
- Watch the Ionization in this lesson when you get to this slide
15. Electron affinity Section 2Periodic Trends
- The energy change that occurs when an electron is acquired by a
neutral atom is calledelectron affinity.
- Electron affinity generally increases across periods.
- Electron affinity generally decreases down groups.
- All these can be explained by effective nuclear charge and by
the distance of an electron from the nucleus.
16. Electron Affinity Section 2Periodic Trends
- Watch the video on Electron Affinity that is included in this
17. Valence electrons Section 2Periodic Trends
- Compounds form because electrons are lost, gained, or shared
- Electrons involved in this behavior are calledvalence
- Valence electrons are the outermost energy level electrons in
- Atoms tend to want to have a full set of 8 valence electrons to
18. Valence electrons Section 2Periodic Trends
- Watch the video on Valence electrons included in this
19. Electronegativity Section 2Periodic Trends
- Valence electrons hold atoms together in compounds.
- In many compounds, the negative charge of the electrons is
concentrated closer to one atom than another.
20. Electronegativity Section 2Periodic Trends
- Electronegativity is the ability of an atom in a compound to
attract electrons from another atom in the compound.
- Electronegativity generallyincreases across rows,anddecreases
down a group
21. Electronegativity Section 2Periodic Trends
- Watch the video on Electronegativity found in this lesson.
22. Summary of periodic trends Section 2Periodic Trends