Tour of the Periodic Table - PowerPoint Presentation

Slide1

Tour of the Periodic Table

4.2

Main Group Elements A

The main group elements are group A elements: 1-8, and they do not include the transition metals or the rare earth elements (lanthanides and the actinides).

Following the Octet Rule

Almost all elements will want to have a full outer shell. This is the most stable electron configuration for an element.

The outer shell will have 2 electrons for period 1, or 8 electrons for periods 2-7.

Exception

Group 8, the noble gases, have a full outer shell

(Helium = 2 electrons, all others have 8 electrons) and so they will not form ions.

Octet Rules

The other elements will either lose or gain electrons to have a full outer shell

. How many they will lose or gain depends on how close they are to having 8 valence electrons.

Groups 1 – 3 will lose their valence electrons so they can have a full outer shell by exposing the shell underneath. It is less energy to lose than to gain.

Exception is H, which is not a group 1 element anyways – can gain 1 electron to become more stable with a full outer shell of 2 electrons or less stable to become the H+ ion.

Octet Rules

2.

Groups 5-7 will gain electrons to obtain a full outer shell. It is less energy to gain a fewer number of electrons than to lose.

3. Group 4 will either gain or lose electrons to obtain a full outer shell.

4. Group 8 – Noble Gasses - will neither gain or lose electrons. They are already stable.

Determine the ion charge for a given element

Also write the symbol with the superscript and charge:

1

. For Na: how many valence electrons? How many electrons will it lose or gain?

For N: how many valence electrons? How many electrons will it lose or gain?

For Ne: how many valence electrons? How many will it lose or gain?

For C: how many valence electrons? How many will it lose or gain electrons?

Answers

1.

Na has 1 valence electron, it will lose 1 and become Na

+

2. N has 5 valence electrons, it will gain 3 and become N

3-

3. Ne has 8 valence electrons, it will not gain or lose electrons, Ne

4. C can gain or lose 4 electrons, either C

4+

or C

4-

Most Reactive Groups

An element becomes more reactive the closer they get to achieving 8 valence electrons. So Groups 1 and 7 are the most reactive groups.

Because they

have only one electron to move.

Reactivity Depends on Electrons

The Alkali metals (very reactive) = group 1

The Alkaline metals (less reactive) = group 2

Semi-metals, Metalloids, Semi-conductors = Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium (not that reactive) have both properties of metals and non-metals.

The halogens (very reactive non-metals) = 7

The noble gases (stable, non-reactive non-metals) = 8

Transition Metals, Lanthanides and Actinides

Transition metals are in the middle of the periodic table and the Lanthanides and Actinides are the last 2 rows that are separated from the periodic table.

Hydrogen

Hydrogen is in a class by itself because it has different properties when compared to the other elements. So it is not a part of the group 1 Alkali metals or any other group. It is very reactive because it wants 1 more electron to have 2 valence electrons in its outer shell = full outer shell. It usually does this by sharing 2 electrons between 2 hydrogen atoms and forming diatomic hydrogen, H

2

.

The Staircase separates Metals and the Non-metals

Metals make up most of the Periodic Table. The staircase that is on the right side of the table divides the metals from the non-metals.

Metals are on the left side of the staircase and non-metals are on the right side of the staircase.

Know that semi-metals hug the staircase.

Classwork

For elements 1-20:

1. Write how many valence electrons it has when neutral

2. Write how many electrons it will gain or lose to get 8 valence electrons or a full outer shell.

3. Write the element symbol and charge

Octet Rule: Groups 1-3 lose, Groups 5-7 gain, Group 8 does nothing, Group 4 can lose or gain

Examples:

1. H : 1 valence electron, gain 1 to have full outer shell, H

-

or can lose one electron H

+

2

. He = 2 valence electrons, will do nothing, He

3. Li = 1 valence electron, will lose 1 electron, Li+

4. Be = 2 valence electrons, will lose 2 electrons, Be+2

5. B = 3 valence electrons, will lose 3 electrons, B+3

6. C = 4 valence electrons, can lose or gain 4, C+4, C-4

7. N = 5 valence electrons, will gain 3 electrons, N-3

8. O = 6 valence electrons, will gain 2 electrons, O-2

9. F = 7 valence electrons, will gain 1 electron, F-

10. Ne = 8 valence electrons, it will do nothing, Ne

11. Na = 1 valence electron, lose 1 e, Na+

12. Mg = 2 valence electrons, lose 2 e, Mg+2

13. Al = 3 valence electrons, lose 3 e, Al+3

14. Si = 4 valence electrons, lose or gain 4, Si+4, Si-4

15. P = 5 valence electrons, gain 3, P-3

16. S = 6 valence electrons, gain 2, S-2

17. Cl = 7 valence electrons, gain 1, Cl-

18.

Ar

= 8 valence electrons, does nothing,

Ar

19. K = 1 valence electrons, lose 1 e, K+

20. Ca = 2 valence electrons, lose 2 e, Ca+2

Li = 1 valence electron, lose 1 electron to have 2 valence electrons.

Be ?

Be = 2 valence electrons, lose 2 electrons to have 2

C?

C = 4 valence electrons, can gain 4 to have 8 or lose 4 electrons to have 2 in the bottom shell.

B = ?

B = 3 valence electrons, will lose 3 to get 2 in the bottom shell.