THEORY OF ATOM

THEORY OF ATOMS

In this material I will explain the atomic structure, and as an introduction we will learn about the atomic model. The atomic model we will study there are five, the first is the atomic model of Dalton, the second model of the Thomson atom, The third Rutherford atom model, the fourth Bohr atom model, the fifth model of quantum mechanics. From this atom model we will obtain an electron configuration that can determine the properties of an atom. Then we will also learn about atomic number, mass number, isotope, isobar, isoton and isoelectron.

1.      the Dalton atom model

Dalton was born in England in 1776, he was a teacher and he studied chemistry and initiated the first theory in chemistry about tom in 1808. The basis of the atomic theory is the first is the lavoisier law, where the mass before the reaction must be equal to the mass after the reaction. The second is Boyle's law where the pressure at times of volume is constant. The third is about the theory of celaya particles from neutrons. The fourth is the fixed comparison law of the proust. Of these four basic theories, Dalton conceived his atomic theory:

1. Each element consists of small particles that can not be divided again called the atom.

2. The atomic elements are identical, the atoms of different elements have different properties and different masses.

3. The atoms of an element can not be converted into other elements.

4. Atoms of some elements can form compounds.

Excess Dalton Atomic Model and Weakness of Dalton Atomic Model

A. Excess Dalton Atomic Model

• The atomic theory of dalton is a central theory that makes other scientists interested in studying atoms so deeply that there are more complex atomic models.

B. Weakness of Atomic Dalton Model

• Can not explain the electrical properties of the material

• It does not explain the differences between atoms with one another

• Can not explain how the atoms are related

• Atoms can actually make particles smaller ... this goes against the dalton theory that atoms can not be subdivided.

2.      Thomson's atomic theory

Joseph John Thomson or J.J. Thomson was a British physicist who discovered the electrons of a particle having a lighter negative charge than atoms in 1897. The electrons are subatomic particles and thereby, Thomson hypothesized: "because electrons are negatively charged, while atoms are electrically neutral then there must be A positive electric charge that offsets the charge of electrons in the atom ". So he proposed an atomic model known as the atomic model of raisin bread that is as follows ..

1. Atoms are shaped like solid spheres that have a homogeneous positive charge (likened to bread)

2. Negatively charged electrons are scattered in them (like raisins spread in bread).

Some of the advantages and disadvantages of Thomson's atom model theory can be seen below ...

Advantages of Thomson Atomic Model Theory

• Can explain the existence of particles smaller than atoms called subatomic

• Can explain the electrical properties of atoms

Weakness of Thomson Atomic Model Theory

• Can not explain the phenomenon of blurring of alpha particles by the gold membranes that Rutherford proposes

• Unable to explain the existence of an atomic nucleus

The third is Rutherford's atomic theory

In 1911 Rutherford denied the truth of Thomson's atomic theory that the atom was positively charged, and around it there was a negatively charged electron like a raisin bread. Rutherford's atomic theory says that the atom has a nucleus that is the center of mass then called the nucleus, surrounded by a cloud of negatively charged electrons.

3.      Rutherford's Atomic Theory

Rutherford conducted a study of the scattering of α (alpha) rays on gold plates. The results of these observations were developed in the Rutherford model atomic hypothesis:

 Most of the atoms are blank or empty surfaces.

The atom has a positively charged atomic nucleus that is the center of the atomic mass.

 Electrons move around the core at very high speeds.

 Most particles pass through without a deflection

 Most of α particles pass without experiencing deflection / obstacle. A small part is deflected, and very little is reflected.

 The electron cloud does not affect the spread of alpha particles.

Advantages of Rutherford Atomic Models

 Easy to understand to explain complex atomic structures

 Can explain the shape of the electron path that surrounds the atomic nucleus

 Can describe electrons motion around the core

Weakness of Rutherford's Atomic Model

 According to the laws of classical physics, electrons moving around the nucleus emit energy in the form of electromagnetic waves. As a result, over time the electrons will run out of energy and eventually stick to the nucleus.

The rutherford atom model has not been able to explain where the electrons are and how they rotate against the atomic nucleus.

 Electrons emit energy when moving, so that the atomic energy becomes unstable.

 Can not explain the line spectrum on hydrogen atom (H).

The fourth theory of Borne's niels atom

A Danish physicist, Niels Bohr (1885-1962) developed the deficiency of the atomic theory put forward by Rutherford. Rutherford's atomic model states that the atom consists of a positively charged nucleus with the electrons surrounding the nucleus, this atom model can also be viewed like our solar system where the sun is the nucleus and the planets as electrons.

5.      Atom Niels Bohr Model

• The electrons in an atom can only cross certain paths called skin shells or energy levels, ie the path at which the electrons are at stationary states, meaning they do not radiate energy.

• The position of electrons in the skin-skin, energy levels can be likened to the position of a person who is on the stairs. One can only be on the first, second, third, and so on, but it is impossible to be between those steps.

2. Rutherford's atomic rigidity was improved by Niels Bohr:

• The electrons that surround the nucleus have certain paths and energies.

• In certain orbital, electron energy is fixed. The electrons will absorb energy if they move to a more outer orbitals and will liberate energy if they move to a deeper orbitals.

3. Bohr atoms

• the skin for which electrons are moved consists of several.

• Borh's atomic weakness.

• Can not explain Zeeman effect and Strack effect.

• Can not explain events in chemical bonds well.

5. Atomic Theory of Quantum Mechanics

1. The Atomic Theory of Quantum Mechanics

• The nucleus of the atom is composed of protons (p) positively charged 1 (+1) and neutral (n) uncharged (neutral) surrounded by negatively charged electrons 1 (-1sub skin composed of orbital (electron space).

• Electrons circulate around the core through the lowest starting skin path as skin No.1, then skin No.2, and so on.

• electron shell composed of sub skin.

• The sub skin is composed of orbitals (electron spaces).

• skin, sub skin, orbital and circulation of electrons are determined by quantum numbers

2. The Weakness of Atomic Theory of Quantum Mechanics

• Can only explain atoms that have single electrons like hydrogen gas but can not explain the color spectrum of atoms that have many electrons.

3. Advantages of Atomic Theory of Quantum Mechanics

• Able to prove that there is an electron path for a hydrogen atom.

Please watch my video



https://youtu.be/NF56ivXiNso

RPP CHEMISTRY CURICULUM 2013

LESSON PLAN



Subject: Chemistry
Class / Semester: XI
Subject: COLLOID
Allocation Time: 2 x 45 minutes

I. CORE COMPETENCY
1. Living and practicing the religious teachings that he embraces
2. Living and practicing honest, disciplined, responsible, caring (polite, cooperative, tolerant, peaceful) behavior, courteous, responsive and proactive and showing attitude as part of the solution to problems in interacting effectively with the social and natural environment And in placing ourselves as a reflection of the nation in the association of the world.
3. Understand, apply, analyze factual, conceptual, procedural knowledge based on his or her knowledge of science, technology, art, culture, and humanities with the insights of humanity, nationality, state and civilization on the causes of phenomena and events, and apply procedural knowledge to the field Specific studies according to his or her talents and interests to solve problems.
4. Processing, reasoning, and presenting in the realm of concrete and abstract realms related to the development of the self-study in the school independently, and able to use methods according to scientific rules

II. BASIC COMPETENCIES
1. Analyzing the role of colloids in life based on their properties.
2. Explain the system and properties of colloids and their application in daily life.

III. INDICATOR
1. Grouping colloidal types based on the dispersed and dispersed phases.
2. Describe the properties of colloids.
3. Explain the lyophob and lyophil colloids

IV. LEARNING OBJECTIVES
1. After studying this material, students are expected to be able to explain the properties of colloids.
2. Students are able to classify the properties of colloids
3. Students are able to analyze the properties of the colloids through discussion

V. TEACHING MATERIALS
Colloid is a mixture of two or more substances in which one of the phases is suspended as a large number of very small particles in the second phase. The dispersed agent and its buffer medium may be any combination of gases, liquids, or solids. Today the term colloid is used to express the size of particles as well as mixed systems. The particles of a substance are said to be colloidal in size between 10-5 cm to 10-7 cm in diameter. The so-called colloidal system is a mixture of substances in which a substance is spread evenly with colloidal sizes in another substance. As well as solutions made up of solutes and solvents, the colloidal system is also composed of two components, namely the phase
Dispersed, ie uniformly distributed substances, and dispersing phases, the medium substances in which the colloidal particles are dispersed.
1. Tyndall effect
The Tyndall effect is a form of optical properties possessed by the colloidal system. In 1869, Tyndall discovered that if a light beam is passed to the colloidal system the light beam appears. But if the same light beam is passed to a true solution, the light beam will not be visible. In short the Tyndall effect is the effect of light scattering by the colloidal system.
2. Brownian motion
The colloidal system also has kinetic properties in addition to the optical properties described above. This kinetic property can occur because it is caused by thermal movement and gravity. These two things cause the colloid system to move zigzag. This movement was first discovered by a biologist named Robert Brown who make observations on pollen by using a microscope, so called Brownian motion.
3. Dialysis
The movement of ions and small molecules through the semipermeable membrane (which colloidal passability can not pass) is called dialysis.
4. Electrophoresis
Electrophoresis is the movement of colloid particles due to the influence of electric fields. Because the colloidal particles have a charge it can move in an electric field. If the colloid is fed direct current through the electrode, then the positively charged colloid will move toward the negative electrode and arrive at the negative electrode will be neutralizing the charge and the colloid will agglomerate
5. Coagulation
The process of clumping of colloidal particles and its precipitation is called Coagulation. With the occurrence of coagulation, means dispersed substances no longer form colloids. Coagulation may occur physically such as heating, cooling and stirring or chemically such as the addition of electrolytes, mixing different colloidal loads.
6. Adsorbtion
Some colloidal systems have properties that can absorb (adsorption) on particles or ions or other compounds. Absorption on the surface is called adsorption, whereas absorption up to the inner layer is called absorption. This absorption force causes some colloidal systems to have a certain charge as the charge is absorbed.

VI. LEARNING MODEL
1. Learning method: cooperative (TTW)
2. Approach: scientific
3. Lecture and discussion

VII. Media And Learning Resources
• Media: whiteboards, markers, laptops, LCDs, LKS
• Source: a. Chemistry book 2: for SMA / MA class XI, author Ari Harnanto and Ruminten: Depdiknas
b.. Chemistry book: SMA / MA class XI, writer Shidiq Premono, Anis Wardani and Nur Hidayati: Depdiknas

VIII. LEARNING STEPS

Activities	Time	Information
preliminary • Teacher checks student attendance   • Teachers deliver learning objectives Apperception • Teacher asks students about material related to colloid. Motivation • Teachers motivate students by conveying natural phenomena related to learning materials and asking questions to guide and explore students' knowledge of the material to be learned.	5’ 4’ 3’ 4’	For example: who knows what is a solution? For example: who knows, what exactly are ice cream we often eat?
Core activities   • Teacher displays slides on colloids Exploration   • Teacher distributes LKS to students who have problems about the type and nature of the colloids   • Students are asked to read and make small notes about what they know and do not know from the problems contained in the LKS. Elaboration   • Students are asked to sit in groups   • Students are asked to discuss the results of their small notes within the group and analyze problems related to the properties of colloids.   • Students are asked to solve the problems contained in the LKS   • Students are required to produce an individual report on the formulation of knowledge about colloidal types, colloidal properties, and solving problems that have been discussed in groups Confirmation   • With the help of the students, the teacher draws the group for the presentation, then 1 selected group of students is facilitated to present the results of the group discussio   • Students from other groups are asked to respond and comment on the results of discussions of their group of friends in polite and courteous language   • One of the students from the group representative was asked to present the answer to the question and the other students were asked to respond.   • Teachers respond to student discussion results	5’ 3’ 8’ 5’ 15’ 10’ 10’ 15’ 5’ 5’ 4’	Post comments on student performance
Cover • Students are asked to make inferences of the types and properties of colloids   Reflection • Teacher asks students about the lesson that has been passed today   • Teacher has a quiz on the type and nature of colloids.   • Teacher assigns homework to students	1.       5’ 6’ 20’ 4’	The question is attached Create a colloid role table in everyday life (individual)

IX .. ASSESSMENT
Rated aspect:
- Cognitive. This assessment is derived from the practice of the LKS and the evaluation questions that are done individually.
- Affective. In accordance with the affective ratings sheet
Indicators of the development of religious attitudes, responsibility, caring, responsive, and polite.

AFFILIATED ASSESSMENT SHEET

Subjects                :............................................... ................................
Class / Semester   : .............................................. .................................
School year          :............................................... ................................
Observation time  : ............................................... ...............................

1. BT (not shown) if it does not show any real effort in completing the task
2. MT (starting to appear) if it shows there is already serious effort in completing the task but still little
3. MB (start developing) if it shows there is a serious effort in completing the task quite often
  4. Constitutional Court (entrepreneurship) if it shows a serious effort in completing the task continuously and consistently
Give a check mark (tick) on the columns according to the observation

No

student's name

Religious

Responsible

Care

Responsive

Good

BT

MT

MB

MK

BT

MT

MB

MK

BT

MT

MB

MK

BT

MT

MB

MK

BT

MT

MB

MK

1.

2.

3.

4.

5.

...

 Information:

1 BT = less             3 MB = good

2 MT = medium     4 MK = very good