STRUCTURE AND PROPERTIES OF MATTER. Independent Reading. Read chapter 3 (starting on page 118) of your text. Answer the following questions. How do scientists explain the northern lights? How does this differ from earlier beliefs?
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Read chapter 3 (starting on page 118) of your text. Answer the following questions.
9) In what ways did Rutherford’s model of the atom differ from Thomson’s?
10) In the last four years of the nineteenth century, scientists in France discovered that certain elements are ______________.
11) What is radioactivity?
Visible portion of spectrum is called continuous.
AN ELECTRON OF ONE OF THE ATOMS ABSORBS ENERGY AND IS EXCITED TO A HIGHER ENERGY LEVEL.
When an electron falls to a lower energy level, it emits light of certain energy.
Each fall through energy levels has a distinct/discrete amount of energy emitted.
- E.g. Electron: moving at a speed of 5.9 x 106 m/s has a wavelength of 1x10-10 m. The size of this wavelength is greater than the size of the hydrogen atom to which it belongs.
A: probability of finding an electron at any point in space when the electron is at the lowest energy level. Probability is never 0.
Notice: first two electrons of lithium’s quantum numbers occupy the 1st orbital same as helium.
Electron configuration: shorthand notation showing the number and arrangement of electrons in its orbitals.
For example, Nitrogen (Z=7): 1s22s22p2 3s1
What about Oxygen (Z=8): ______________
The energy of each orbital (or group of orbitals) increases as you move from left to right.
The number of electrons that each sublevel can ‘contain:’
s = 2
p = 6
d = 10
f = 14
1) Fill each lower n level with maximum amount of electrons first.
2) Spread electrons out in each ‘remaining” orbitals.
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p
For example, Nitrogen (Z=7) has 7 electrons when neutral. Therefore, nitrogen will have the following electron configuration:
Write the complete electron configuration and complete orbital diagrams for the following elements:
1s2 2s2p6 3s2p6d10 4s2p6d10f14 5s2p6d10f3 6s2p6d1 7s2
YIKES.DO WE REALLY WANT TO WRITE ALL OF THIS OUT EVERY TIME?
CONDENSED ELECTRON CONFIGURATIONS ARE CONVENIENT SHORT FORMS: SODIUM DOES NOT HAVE 1 ELECTRON!
Experimental evidence indicates that chromium and copper are most stable with configurations that do not follow the rules.
HW: # 8 & 9.
Valence electrons: number of electrons in the outer energy level, n. (Remember Lewis Dot Diagrams?)
How many valence electrons do the following have:
Read “Summarizing Characteristics of s,p,d and f Block Elements” on page 149 for more information.
#11-12 for HW.
Ionization Energy: energy needed to completely remove one electron from a ground state gaseous atom.
When n=∞, electron completely removed.
IE1 : First ionization energy.
Low IE1 – form cations.
Group 1 – very reactive.
High IE1- form anions.
‘Drops’ in Ionization Energy:
1)Group 13 – electrons start to fill thenporbitals. Electron more easily removed.
2) Group 16 – np3 is more stable than np4. np4 experiences electric repulsions with np3, and so increased orbital energy in O. Electron more easily removed.
Decreases down a group: inverse of radii. As radius increases, distance of valence electrons from the nucleus also increases. Less energy needed.
Increases across a period: inverse of radii. Radius decreases as
Zeff increases, and more energy needed.
Electron Affinity: change in energy that occurs when an electron is added to a gaseous atom.
- more than one value.
- first EA results in anion with 1- charge.
- Ease in which it gains an electron is reflected in its high electron affinity.