CHAPTER 1 PERIODIC SYSTEM OF THE ELEMENTS AND ATOMIC STRUCTURE Sistem Periodik Unsur dan Struktur Atom

Teaching Learning Objectives The student can explain of Dalton’s atomic theory. The student can explain of Thomson’s atomic theory. The student can explain of Rutherford’s atomic theory. The student can explain of Neils Bohr’s atomic theory.

A. Model and Theory of Atom Democritus’ Atomic Theory According to Democritus, if a stone divided, and we did that repeatedly until it is undivided any more, every pieces of that stone had the same character with its origin. He labeled the smallest piece of stone as atomos (A=no, TOMos=divided), which mean “invisible”. Based on his theory, every atom that constructed different matter is dissimilar.

The Greek Model Democritus - A Greek Philosopher around the year 400 BC. Democritus concluded that matter could not be divided into smaller and smaller pieces forever. Eventually, the smallest piece of matter would be found. He used the word "Atomos" to describe the smallest possible piece of matter.

ATOMIC THEORY OF DALTON A substance consist of minute particles that can’t be divided, and this is called an atom with a small massive ball shape Atoms of an element are identical but they are different from atoms of the other elements Chemically, atoms are interwoven to each other to perform a molecule with a simple comparison A compound is the product of the reaction of atom An atom of an element is permanent, can’t de divided or created or destroyed Atom model of Dalton

2. Dalton’s Atomic Theory and Model Dalton suggested as followed : Atom is the smallest particle of matter Atom is small sizes and round-shaped, indivisible, neither created nor destoyed. All atoms of given element are identical Atoms of different element can be joined to produce substance with fixed scale. Atoms combine to make compounds: a given compound always has the same relative number and kind of atoms

3. Thomson’s Atomic Theory and Model Whithin the experiment, by use of the cathode ray discovered by Thomson soon called as electron. Based on this founding, Thomson suggested his atomic model, known as Plum-pudding. Thomson argued that atom was ball-shapped with positive charge, and its negative charge electrons were spread inside the ball. He pictured the small electrons to be embedded in the atom much like raisins in a pudding.

4. Rutherford’s Atomic Theory and Model Berdasarkan percobaan penembakan partikel ∂ pada lempeng emas yang sangant tipis, Rutherford deduced as follow: 1. Atom is built from positively charged nucleus and negatively charged electron around the atoms nucleus. 2. Atom is neutral charge, so that the positive particle (proton) and negative particle (electron) have the same amount.

5. Bohr’s Model and Atomic Theory Bohr’s atomic theory can be comprehended as follow; Electrons are moving around nucleus in discreet level of energy. Electrons may tranfer from one energy level to another energy level, 1. From low energy to upper level is called excitation, and it absorbs energy, 2. From high energy to upper level is called de-excitation, and it releases energy.

PARTIKEL DASAR ATOM Partikel Atom Lambang Massa Muatan Penemu gram sma Coulomb Pembu lat an Proton Neutron Elektron 11p 10 n 0-1e 1,67 x 10-24 9,11 x 10-28 1,007276 1,008665 0,000548 +1,602x10-19 -1,602x10-19 +1 -1 Goldstein Chadwick Thomson

B. Application of Chemical Element Periodic Table Calculate the Amount of Proton, Electron and Neutron of Atom X : atom or elements symbol AzX A : mass number= the total amount of proton and neutron Z : atomic number = the amount of proton

2311 Na 2311 Na+ Example : Atom Na is neutral atom Atomic number = z = 11 = proton number = electron number Mass number = A= 23 = proton + neutron number Neutron number = 23 – 11 = 12 2311 Na+ Atom Na+ is positive ion Atomic number = z = 11 = proton number Mass number = A= 23 = proton + neutron number Neutron number = 23 – 11 = 12 Electron number = Z – charge = 11 – (+1) = 10

Isotop, Isobar, Isoton Isotop adalah atom-atom sejenis yang memiliki Z sama A berbeda Contoh : 166O, 176O dan 186O Isobar adalah atom-atom yang memiliki A sama Z berbeda. Contoh : 2411Na dan 2412Mg Isoton adalah atom-atom yang memiliki jumlah netron sama. Contoh : 2311Na dan 2412Mg

2. Electron Configuration Electron Configuration is construction of electron in atom shells The maximum amount in every shell is 2n2 Shell (n) Max Electron Number (2n2) 1 2 3 4 8 18 32

Atomic Electron Configuration Element Atomic Shell Valence Electron K L M N O P Q 3Li 2 1 1 9F 2 7 7 11Na 2 8 1 1 1 19K 2 8 8 1

3. The Atomic Relative Mass of Element The atomic relative mass of element is perbandingan massa rata-rata 1 atom suatu unsur dengan 1/12 massa 1 atom C-12. Relative atomic mass= One atomic mass 1/12 x one atomic mass of C-12 Example : Mass 1 atom O Ar O = Assuming mass of 1 atom oxygen is 2,6505x 10-24 gram, and mass avarage 1 C-12 is 2 x 10-24gram, how much is the atomic relative mass of oxygen ? 1/12 mass 1 atom C-12 2,6505 x 10-24gram Ar O = = 16 1/12 x 2 x 10-24gram