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“Electron configuration and valence electron”

Competency Standards       : 1. Determine the atomic structure, periodic properties of elements and chemical bonds and molecular structure and properties

Basic Competency            : 1.1 identify the atom, atomic structure, the properties of elements, relative atomic mass, and the periodic properties of the periodic table

INDICATOR

- Determine the type and period elements in the periodic table

- Determine the valence electron of elements  from electron   configuration

MATERIALS

ELECTRON CONFIGURATION AND VALENCE ELECTRON

Electrons are atomic particles that are very light so that its mass is negligible and is considered equal to zero. In an atom, the number of electrons equals the number of protons, but kind of opposite charge. The location is outside the core electron. That is contained in the electron trajectories.

According to Bohr's atomic theory, electrons are in a particular orbital trajectory or the so called shell electron. Each shell has a certain energy level. The closer to the nucleus, the smaller the energy level. Conversely, the farther from the nucleus, the greater the energy level. Based on its distance from the nucleus, there are some shell.

First shell or K shell

Second shell or L shell

Third shell or M shell

Fourth shell or N shell

K shell < L shell < M shell < N shell

Based on the sequence of energy levels can be written as follows:

a.      Electron configuration

Electrons in the atom is composed based on the level of energy. Preparation of the electron is known as the electron configuration. There are two ways of preparation of the electron, namely:

-          How a shell (K L M N) and

-          How a subshell (s p d f)

The second way (a subshell) will be discussed in class XI. Currently, you will only be allowed with the electron configurations per shell (KLMN).

Electron configuration of a shell based on the maximum number of electrons that can fill each shell according to the formula

Σ e maximum a shell = 2 (n²)

n indicates the price of the occupied electron shell.

The maximum number of electrons in every shell

Electron charging sequence starting from the shell which has the lowest energy level, then the next shell that has a higher energy, until at last the shell that will be occupied by the electron rest.

How if the number of electrons that are available do not reach the maximum number of electrons in the shell, even greater than the maximum electron shell before? If so, that would be occupied electron shell should use the same number of electrons with the maximum number of electrons in the shell before.

a.      Valence electron

Valence electron is an electron that is located on the outer shell so that have the highest energy level. This valence electrons involved in chemical reactions. Outer shell electrons can be separated, interchanged, or used in conjunction with other atoms to form bonds between atoms. In other words, the chemical nature of atoms is determined by the valence electron.

How do I determine the valence electron? Valence electrons can be determined by using electron configuration.

Determination of the valence electron from the electron configuration
By determining the electron configuration, you can know the number of electrons in its outer shell.

b.      Relationship type, period, electron configuration and valence electron

You have studied the group, period, electron configuration and valence electron, is there any relationship between these four things?

Class of an element shows the number of valence electrons. The period of an element indicates the amount of shell that has been charged electron. Valence electron and the amount of shell that has been filled electron can be determined from the electron configuration. Thus, it can be seen from the electron configuration of the group number and period of an element.

QUESTION

1. Write the electron configuration of the following elements:

a. ₉F

b. ₁₁Na

c. ₂₀Ca

d. ₃₇Rb

e. ₅₅Cs

f. ₈₅At

2. Determine the number of valence electrons of atoms ₃₅Br

3. Determine the type and period of the following elements!

a. ₇N

b. ₁₂Mg

c. ₃₃As

d. ₅₄Xe

e. ₈₂Pb

ANSWER

1.      Electron configuration from :

a. ₉F : 2 7

b. ₁₁Na : 2 8 1

c. ₂₀Ca : 2 8 8 2

d. ₃₇Rb : 2 8 18 8 1

e. ₅₅Cs : 2 8 18 18 8 1

f. ₈₅At : 2 8 18 32 18 7                                                                        (Score 30)

2. Electron configuration ₃₅Br : 2 8 18 7

In the shell-4 which is the outer shell, there are 7 valence electrons, so the number of  electron ₃₅Br is 7                                                                    (Score 20)

3.      Group and the period of:

a.       Electron configuration ₇N: 2 5
- Valence electrons 5, means the group VA
- There are two shell filled with electrons (n = 2), means a period of 2

b.      Electron configuration ₁₂Mg : 2 8 2

- Valence electrons 2, means the group IIA

- There are three shell filled with electrons (n=3), means a period of 3

c.       Electron configuration ₃₃As : 2 8 18 5

- Valence electrons 5, means the group VA

- There are four shell filled with electrons (n=4), means a period of 4

d.      Electron configuration ₅₄Xe : 2 8 18 18 8

- Valence Electron 8, means the group VIIA

- There are five shell filled with electrons (n=5), means a period of 5

e.       Electron configuration ₈₂Pb : 2 8 18 32 18 4

- Valence Electron 4, means the group IVA

- There are six shell filled with electrons (n=6), means a period of 6       (Score 50)

Final score = total score of each number
The number of total score = 100

The classify of colloid systems

Standard Competence      : 4. Describe the characteristic of solution, measurement method and its application

Basic Competence            : 4.8 Group the colloid systems based on the experiment result and the useful in industry

 Indicator 

a.       Analyze the differences of true solution, colloid, and suspension

b.      Analyze the kinds of colloid system

Materials

Colloid is derived from Greek kolla, meaning glue. Old time glues were colloidal dispersions in water. Colloids, also called colloidal dispersions or colloidal suspensions, are mixtures that are intermediate between true solutions and suspensions. Because of the way the size of colloidal particles compare to the dimensions of the particles of the medium in which they are distributed, we don’t use the terms solute and solvent. Instead, we refer to the dispersed phase and the dispersing medium. Dispersed phase is a substance which is dispersed, while dispersing medium is the medium which used to disperse.

Table 1.1.  The differences of solution, colloid, and suspension

SOLUTION	COLLOID	SUSPENSION
Ex : sugar solution in water	Ex : milk mixture in water	Ex : starch mixture in water
1.       Homogeneous, can not be differentiated although use ultra microscope 2.       All particles have dimension (length, width, tick) less than 1 nm 3.       One phase 4.       Stable 5.       Can not be filtered	1.       Under microscope has homogeneous properties but under ultra microscope has heterogeneous properties 2.       Particles has dimension between 1 nm until 100 nm 3.       Two phases 4.       Generally stable 5.       Can not be filtered except use ultra filter	1.       Heterogeneous 2.       One of particles or all particles have dimension more then 100 nm 3.       Two phases 4.       Not stable 5.       Can be filtered

            Table 1.2.  Types of colloidal dispersions      

Dispersing Medium	Dispersed Phase	Colloid Type	Examples
Solid	Solid	Solid sol	Pearls
Solid	Liquid	Solid emulsion	Cheese
Solid	Gas	Solid foam	Marshmallow
Liquid	Solid	Sol, gel	Paint
Liquid	Liquid	Emulsion	Milk
Liquid	Gas	Foam	Whipped cream
Gas	Solid	Solid aerosols	Smoke
Gas	Liquid	Liquid aerosols	Clouds

Question:

No	Dispersing Medium	Dispersed Phase	Colloid Tape	Examples
1.	Solid	Solid		Pearl, Opals
2.	Solid	Liquid	Solid emulsion
3.	Solid		Solid foam	Marshmallow, pumice
4.	Liquid	Solid	Sol, Gel
5.	Liquid	Liquid	Emulsion
6.		Gas	Foam	Whipped cream, shaving cream
7.	Gas	Solid		Smoke, dust
8.	Gas		Liquid aerosols	Clouds, mist, fog

Answers :

No	Dispersing Medium	Dispersed Phase	Colloid Tape	Examples
1.	Solid	Solid	Solid sol	Pearl, Opals
2.	Solid	Liquid	Solid emulsion	Cheese, butter
3.	Solid	Gas	Solid foam	Marshmallow, pumice
4.	Liquid	Solid	Sol, Gel	Jelly, starch in water, paint
5.	Liquid	Liquid	Emulsion	Milk, ice cream, mayonnaise, lotion
6.	Liquid	Gas	Foam	Whipped cream, shaving cream
7.	Gas	Solid	Solid aerosols	Smoke, dust
8.	Gas	Liquid	Liquid aerosols	Clouds, mist, fog

TOTAL SCORE : 8 x 10 = 80