Скачать или смотреть Chemistry 101 Jeddah Chapter 2 Atoms, Molecules, Ions Periodicity Slide 1-7كيمياء 101 جامعة جدة علمي

Chemistry 101 Jeddah University
شرح منهج الكيمياء 101 لطلبة جامعة جدة علمي
شرح شابتر 2
slides 1 - 7
Atoms, Molecules, Ions and Periodicity
Atoms compose all ordinary matter. The word atom comes from the Greek atomos, meaning :indivisible”. 2.1 Imaging and moving individual atoms 200 years ago, John Dalton proposed his atomic theory. Today, by using scanning tunneling microscope (STM) scientists could see, pick up, move atoms or molecules, and even can begin to build tiny machines out of just a few dozen atoms (an area of research called
nanotechnology).
2.2 Modern atomic theory and the laws that led to it Dalton’s Atomic Theory was developed and accepted by observation and laws. The three most important laws that led to it are; 1- Law of the conservation of matter. 2- Law of Definite Proportions. 3- 2-Law of Multiple Proportions.
1- Law of the conservation of matter: In a chemical reaction, matter is neither created nor destroyed.
The total mass of substances present at the end of a chemical process is the same as the mass of substances present before the process took place. Total mass of used reactants = total mass of products produced.
Total number of reactant atoms = total number of product atoms.
ATOMIC THEORY OF MATTER AND ITS LAWS
• Dalton’s Atomic Theory notes that – “Atoms of different elements can combine to form molecules in simple whole-number combination of atoms.”
• Law of definite proportions
• Law of multiple proportions
2-Law of Definite Proportions • The Law of Constant Composition (or The Law of Definite Proportions). All samples of a given compound, regardless of their source or how they are prepared, have the same proportions of their constituent elements. That means that the relative number of atoms of each element that makes up the compound is the same in any sample.
– For example – A sodium chloride molecule (NaCl) is always a 1:1 ratio of one sodium atom to one chlorine atom – A 100.0 g sample of NaCl contains 39.3 g Na and 60.7 g Cl. Mass Cl
= 60.7 g = 1.54 Mass Na 39.3 g
– A 58.44.0 g sample of Na contains 22.99 g Na and 35.44 g Cl. Mass Cl
= 35.44 g aCl = 1.54 Mass Na
22.99 g
3-Law of Multiple Proportions • When two elements (A and B) can form different compounds, the masses of element B that combine with 1g of element A can be expressed as a ratio of small whole numbers.
• These combinations can be represented as a ratio. – For example • A molecule of carbon dioxide (CO2) has a ratio of one C atom to every two atoms of oxygen or 1:2.
• A molecule of carbon monoxide (CO) has a ratio of one C atom to one atom of oxygen or 1:1
𝑚𝑎𝑠𝑠 𝑜𝑓 𝑂 𝑡𝑜 1𝑔 𝐶 𝑖𝑛 𝐶𝑂2 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑂 𝑡𝑜 1𝑔 𝐶 𝑖𝑛 𝐶𝑂 =
2.67
1.33= 2.0
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