1. Electrons valence electrons borh diagrams
Miss Fogg
Fall 2015

2. Valence Electrons
2-8-8 Rule
Electrons orbit the nucleus in energy levels within the electron cloud
The 1st energy level holds 2 electrons
The 2nd and 3rd energy levels holds 8 electrons 1 2 1 2 1 8 8 3 3 7 7 4 4 2 6 5 6 5

3. Valence Electrons
Valence Electron
Valence electrons: electrons in the last shell or energy level of an atom. 1 2
Last energy level: Level 3 1 2 1 8 3 3
So count the electrons in the last energy level 7 4 4 2 6 5
6 Valence Electrons! 6 5

4. How many valence electrons are in this atom?1 2 3 1 2 1 8 3 3
Valence Electrons 7 4 2 6 5

5. How many valence electrons are in this atom?5 1 2 1 3
Valence Electrons 4 2 5

6. How many valence electrons are in this atom?1 1
Valence Electrons

7. How many valence electrons are in this atom?2 1 2 1
Valence Electrons 2

8. Valence Electrons “Happy" atoms are stable atoms
Atoms are stable when their outermost energy levels (shells) are full 1 2 1 2 1 2 1 1 1 8 3 8 8 3 3 7 4 7 7 4 4 2 2 2
Stable 6 5 6 5
Stable 6 5
Stable

9. Valence Electrons
Is this atom stable? 1 2 1 8 3 7 4 2 6 5
YES!

10. Valence Electrons NO! Is this atom stable? 1 2 1 2 1 8 3 3 7 7 4 4 2 65 6 5
NO!

11. Valence Electrons Sad atoms are not stable
When an atom's outermost shell is not complete/full it is not stable.

12. Valence Electrons
Is this atom unstable? 1 2 1 8 3 7 4 2 6 5
NO!

13. Valence Electrons YES! Is this atom unstable? 1 2 1 2 1 8 3 3 7 7 4 46 5 6 5
YES!

14. Valence Electrons
Sad Atoms
Atoms become stable by bonding (joining) with other elements.
Bonded atoms are called molecules.
A covalent bond is one where atoms share electrons.
An ionic bond is one where electrons are either given or taken, not shared.
A metallic bond is when metal ions share a pool of electrons

15. Bohr Diagrams
We can draw Bohr Models to summarize all the information we know about an element
1 valence electron
Nucleus (with # protons and # neutrons)
8 electrons found on second shell
Sodium (Na)
2 electrons found on first shell

16. How to draw a borh diagram
Draw the nucleus as a circle
Put the # of protons & # of neutrons inside the nucleus
Draw the appropriate # of electron shells around the nucleus
Draw the electrons counter clockwise from the inner shell to the outer shells, following the electron orbital rules
6 - Carbon
6 p+
6 n

17. How to draw a borh diagram
Draw the nucleus as a circle
Put the # of protons & # of neutrons inside the nucleus
Draw the appropriate # of electron shells around the nucleus
Draw the electrons counter clockwise from the inner shell to the outer shells, following the electron orbital rules
7 - Nitrogen
7 p+
7 n

18. How to draw a borh diagram
Draw the nucleus as a circle
Put the # of protons & # of neutrons inside the nucleus
Draw the appropriate # of electron shells around the nucleus
Draw the electrons counter clockwise from the inner shell to the outer shells, following the electron orbital rules
13 - Aluminum
13 p+
14 n

19. Groups = Columns
The elements in a group have the same number of electrons in their outer orbital.
Every element in the first column (group one) has one electron in its outer shell. Every element on the second column (group two) has two electrons in the outer shell. As you keep counting the columns, you'll know how many electrons are in the outer shell.
There are some exceptions to the order when you look at the transition elements, but you get the general idea.

20. Families of elements

21. Hydrogen is special We often consider Hydrogen as its own “family”
Hydrogen is placed at the top of group 1 in the periodic table because it has ns1 electron configuration like the alkali metals.
However, it varies greatly from the alkali metals as it forms cations (H+) more reluctantly than the other alkali metals

22. ALKALI METALS Highly reactive metals Do not occur freely in nature
Least dense of all the metals & very soft

23. ALKLINE EARTH METALS 2nd most reactive group of metals
Do not occur freely in nature
React readily with halogens

24. TRANSITION METALS
These metals have high densities, strengths, and resistant to corrosion
React less quickly to oxygen
Many exist in nature as free elements
YELLOW:

25. Lanthanides Aka “Rare-Earth” elements Oxidize rapidly in moist air
Dissolve quickly in acids

26. Actinides Radioactive due to instability
Most are made synthetically using particle accelerators, are short lasting, and quickly decay into other elements

27. OTHER METALS/Post Transitional
Aka “Poor Metals”
Common to most metals (malleable, ductile, conductors) but have lower melting and boiling points and are softer in comparison

28. Metalloids Generally solids Can be shiny or dull
Used as semiconductors in electronics

29. Other Nonmetals Poor conductors of heat and electricity
Brittle if solid
Dull appearance
Many of these elements make up the majority of living matter

30. HALOGENS
React with metals to form salts
Only occur in nature as compounds because they react quickly with other elements

31. NOBLE GASES
Odorless, colorless, monatomic gases
Very low chemical reactivity (Noble)