03_Atoms, Molecules and Ions(Chemistry).pptx

Chemistry

1. ATOMS, MOLECULES AND IONS Chemistry for Industrial Technologist

2. Development of the Modern Atomic Theory Since the ancient times, philosophers and scientists had been asking “What are things made of?”

3. Greek philosophers pioneered the quest of finding out the basic composition of matter. EMPEDOCLES ( 490-435 B.C.) who proposed the concept of fire, air, water, and earth as the answer. He called these the four elements, composed of minute, unchanging particles. This was then accepted by ARISTOTLE (384-323 B.C.), he even added a 5 the element which he called QUINTESSENCE .

4. These ideas culminated into a primitive concept developed by DEMOCRITUS (460-370 B.C.) who assumed the presence of a void in which the unchanging particles were in continuous random motion. Later he then came up with a theory stating that everything is composed of small indivisible particles which he called ATOMOS .

5. In 1803, English chemist JOHN DALTON proposed that atoms have fixed weights and definite properties. This is known as DALTON’S ATOMIC THEORY . This then led to the pursuit of knowledge about the structure of the atom. SCIENTIST WORKS J.J. Thomson Discovered electron (1897) Robert Millikan Determined the charge of an electron (1909) Ernest Rutherford Discovered nucleus (1911)

6. Law of Conservation of Mass In a chemical reaction, no change in mass takes place. The total mass of the products is equal to the total mass of the reactant. In 1789, Antoine Laurent Lavoisier discovered the law of conservation of mass.

7. Reaction Reactant(s) Product(s) 1) H₂ O₂ H₂O mass 3.4g 10g 13.4g 2) CH₄ O₂ CO₂ H₂O mass 12.2g 14g 6.2g 20g 3) HgO Hg O₂ mass 23.6g 10.6g 13g 4) Li O₂ Li₂O mass 18.9g 5.7g 24.6g 5) C₃H₆ O₂ CO₂ H₂O mass 18.9g 11.1g 14.4g 15.6g 6) Al(OH)₃ Al₂O ₃ H₂O mass 31.5g 21.8g 9.7g

8. Hydrogen and oxygen react chemically to form water. How much water would form if 14.8 grams of hydrogen reacted with 34.8 grams of oxygen? (H₂+ O₂ → H₂O) H₂ + O₂ → H₂O Reactant side → Product side 14.8g + 34.8g → 49.6g

9. Law of Definite Proportion A compound always contains the same constituent elements in a fixed or definite proportion by mass. As an example, any sample of pure water contains 11.19% hydrogen and 88.81% oxygen by mass. It does not matter where the sample of water came from or how it was prepared. Its composition, like that of every other compound, is fixed.

10. For example, when different samples of isooctane (a component of gasoline and one of the standards used in the octane rating system) are analyzed, they are found to have a carbon-to-hydrogen mass ratio of 5.33:1 Sample Carbon Hydrogen Mass Ratio A 14.82g 2.78g = B 22.33g 4.19g = C 19.40g 3.64g = Sample Carbon Hydrogen Mass Ratio A 14.82g 2.78g B 22.33g 4.19g C 19.40g 3.64g

11. Law of Multiple Proportion If two elements can combine to form more than one compound, the masses of one element that will combine with a fixed mass of the other element are in a ratio of small whole numbers.

12. Law of Multiple Proportion It states that when two elements combine to form more than one compound, the ratios of the masses of the second element that combine with a fixed mass of the first element are simple whole numbers.

13. Consider the compounds formed by carbon and oxygen: Carbon monoxide (CO)12 grams of carbon combine with 16 grams of oxygen. Carbon dioxide (CO₂)12 grams of carbon combine with 32 grams of oxygen. In this case, the mass ratios of oxygen that combine with a fixed mass of carbon (12 grams) are 16 grams and 32 grams. The ratio of these masses is a simple whole number:

14. Dalton’s Atomic Theory proposed by John Dalton, can be used to explain the laws of chemical change. This theory is based on the following set of postulates: 1. Elements are made up of very small particles known as atoms.

15. Dalton’s Atomic Theory 2. All the atoms of an element are identical in mass and size, and are different from the atoms of another element. Dalton used the different shapes or figures to represent different elements, as follows:

16. Dalton’s Atomic Theory 3. Compounds are composed of atoms of more than one element, combined in definite ratios with whole number values.

17. Dalton’s Atomic Theory 4. During a chemical reaction, atoms combine, separate, or rearrange. No atoms are created and no atoms disappear.

18. The Atomic Structure

19. The Structure of Atoms An atom is a small, indivisible particle considered to be the basic unit of matter. An atom consists of three main subatomic particles, namely, protons, neutrons, and electrons.

20. Subatomic Particles ELECTRONS are small, negatively charged particles that spin around the nucleus, staying in their ORBITS. The shells are numbered, depending on how close they are to the nucleus. Electrons in the lowest energy level are the ones most tightly bound and, therefore hardest to expel. The number of the energy level is designated. PROTONS were discovered Eugene Goldstein using Crookes tube. Protons are positively charged particles. NEUTRONS are found in the nucleus. James Chadwick showed that uncharged particles are emitted when beryllium and other elements are bombarded with high velocity helium particles. A neutron has no charge.

21. PARTICLE LOCATION CHARGE RELATIVE MASS PROTON Nucleus +1 1 ELECTRON Outside nucleus -1 0.0006 NEUTRON Nucleus 1

22. a. Atomic number = number of protons = number of electrons in a neutral atom b. Mass number = number of protons + number of neutrons Representing an Atom

23. ATOMIC NUMBER MASS NUMBER NUMBER OF PROTON NUMBER OF ELECTRONS NUMBER OF NEUTRON 4 9 4 4 5 14 28 14 14 14 8 17 8 8 9 11 23 11 11 12 24 52 24 24 28 19 39 19 19 20

24. atoms of an element having the same atomic number but different mass number . The existence of isotopes was shown by mass spectroscopy experiments, wherein elements were found to be composed of several types of atoms, each with different masses. Isotopes

25. Protium is the most common isotope of hydrogen and also the most abundant in nature. The basic hydrogen atom – a single proton circled by a single electron Deuterium is sometimes called heavy hydrogen because it is more massive than protium. The isotope deuterium has one proton, one neutron and one electron. Tritium is a hydrogen atom that has two neutrons in the nucleus and one proton. Isotopes

26. Molecules and Ions Not all matter is atomic in nature. Most matter exist in nature in the forms of molecules, ions and compounds.

27. are made up of atoms that are chemically bonded together. DIATOMIC MOLECULES contain only two atoms and normally occur in nature. If the atoms are of the same element, they are called HOMONUCLEAR. If they are of different elements, they are called HETERONUCLEAR. Homonuclear diatomic molecules examples: H2, Cl2, and Br2 .Heteronuclear diatomic molecules examples: HCl, NO, and HF. On the other hand, a polyatomic molecule contains three or more atoms. Examples: O3, CO2, and C2H2. Molecules

28. are atoms or molecules that have charge, meaning the number protons is not equal to the number of electrons, giving the atom either a positive or negative net charge. Ions with positive charge are called CATIONS while ions with negative charge are called ANIONS . Ions

29. Chemical Formulas Writing chemical is a way of expressing in symbols the elements present in a compound, as well as the number of atoms of each element present in the compound.

30. Indicates how the atoms are arranged and bonded chemically. They are graphical representations of compounds showing the elements connected to each other in symbols and how they are arranged in the molecule of the compound. Structural Formula

31. A formula that shows the number of atoms per element present in a compound. It is also called the true formula. Molecular Formula

32. Shows the simplest form of the atomic ratio in a chemical compound. Empirical Formula

33. Naming Compounds There are certain rules to follow when naming compounds. Ionic and molecular compounds use different nomenclature rules.

34. is a neutrally-charged compound that contains a cation that are usually metallic and anion that are usually non-metallic. Rules: a. Name the metal b. If the metal has more than one oxidation state, indicate the charge of the metal cation using Roman numerals and enclose it in parentheses or use suffixes – ous and – ic . c. If the anion is monoatomic, add the suffix –ide to the root of the name of the non-metal. A MONOATOMIC ANION is made up of only one atom. A POLYATOMIC ANION is made up of more than one atom of different elements. Naming Ionic

35. What is the chemical name of the following Ionic compounds KCl KNO₃ FEI₂ Cu(NO₃) ₂

36. Write the chemical formula of the following ionic compounds. Sodium hydroxide Aluminum phosphate

37. A molecular compound is composed of non-metallic elements. Rules: 1. Use prefixes for both elements in the compound to indicate the number of atom for each elements present in the compound. If there is only 1 atom in the first element, the prefix “mono” is usually dropped. Naming Molecular Compounds 1 mono- 2 di- 3 tri- 4 tetra- 5 penta- 6 hexa- 7 hepta - 8 octa- 9 nona - 10 deca -

38. 2. Add the suffix –ide to the root of the name of the second element. What is the chemical name of the following molecular compounds. 1. SF6 2. P2S3 Write the chemical formula of the following molecular compounds. 1. Carbon tetrafluoride 2. Diphosphorus pentaoxide Naming Molecular Compounds