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Atoms
- 2. Greek Philosophers •Aristotle 4Elements of matter -Earth -Fire -Air -Water
- 3. Matter is made of atoms (cannot be further divided), the word atom comes from the Greek word “atomos” which means indivisible. Democritus
- 4. • Atoms were tiny particles that could not be divided • John Dalton proposed that an atom is a sphere of matter that is the same throughout and can’t be seen by human eyes • Marble Model
- 5. • Came up with the idea of the electron negatively charged particle • Thomson discovered that all atoms contain electrons, which are tiny, negatively charged particles. Thomson proposed that an atom is a sphere of positive charge. The electrons are mixed uniformly in the sphere. • Cookie Model
- 6. Ernest Rutherford • He hypothesized that almost all the mass and all the positive charge of an atom is concentrated in an extremely tiny nucleus at the center of the atom.
- 7. • Thought electrons traveled in fixed paths around the nucleus called energy levels.
- 8. Atomic Structure • Arrangement and number of sub-atomic particles •Protons •Neutrons •Electrons
- 9. •Center or core of an atom •Contains 99.9% of the weight of an atom •Contains protons and neutrons
- 10. •Positively Charged Sub-atomic particles •Found in the nucleus •All protons are a like
- 11. •Neutrally charged (no charge) sub-atomic particle •Found in nucleus
- 12. •They are the negatively charged particles orbiting the nucleus. •It is much smaller than the protons and the neutrons .
- 13. What is the net charge of the atom ? • The atom is formed of positively charged proton in the nucleus and negatively charged electrons in the energy level ,but they are equal to each other in number ,making the net charge of the atom “neutral”. No of positive protons = No of negative electrons
- 14. • They are charged atoms • Number of positive protons = Number of negative electrons. Positive ion Negative ion
- 15. If the atom lost an electron ,therefore the number of positive protons are more than the negative electrons making the atom positively charged Positive Ion
- 16. If the atom gained an electron ,therefore the number of negative electrons are more than the positive protons making the atom negatively charged Negative Ion
- 17. • Atomic number is the number of Protons in an atom • All atoms of a particular element have the SAME number of protons (All Carbon atoms have 6 protons) • In a neutral atom, The atomic number =The number of electrons
- 18. • Also called atomic weight or Mass Number • Sum weight of protons and neutrons in an atom
- 19. Calculate the mass number of each of the following atoms
- 20. O 8 16 Atomic number Mass number Symbol OxygenName Atomic number= Number of protons= Number of electrons Mass number= Number of protons + Number of neutrons
- 21. Calculating Neutrons: • Mass number = protons + neutrons so….. • Neutrons = mass number – protons What is the number of neutrons of the following atom ? A 21 45
- 22. • In 1869 Dimitri Mendeleev was working on a way to classify elements. •At the time, more than 60 elements had been discovered. •And he arranged the elements according to their atomic mass Developing a Periodic Table
- 23. 100 table The periodic table is a chart of the elements arranged according to their atomic number in rows and columns according to their physical and chemical properties.
- 26. Symbol
- 27. •The periodic table is a chart of the elements arranged into rows and columns according to their physical and chemical properties. •It can be used to determine the relationships among the elements. What is the periodic table?
- 28. Groups and Periods - Columns in the periodic table represents “groups” - There are 18 groups in the periodic table. - Elements of the same the same group have the same chemical properties as the all have the same number of electron/s in the outer most energy levels.
- 29. - Rows in the periodic table represent “periods”. - There are 7 periods in the periodic table . - Elements of the same period have the same number of energy levels
- 30. The Periodic Table of Elements
- 31. Periodic Table A great deal of information about an element can be gathered from its position on the period table. Understanding the organization and plan of the periodic table will help you obtain basic information about each of the 118 known elements.
- 32. Mass Number Atomic Mass (Mass Number) is the number ……………. __________ Atom p+ n0 e- Mass # Oxygen - 8 - 33 42 - 31 15 ___ ___ ______ ______ ___ ___ ___ ______ ___ ______
- 33. Recall - How are P, N, e- related? • atomic number = # protons • # protons = ……………. • # protons + # neutrons = atomic mass # neutrons = ……………. …………….
- 34. • How many protons, neutrons and electrons are found in an atom of Cs? • _____________ • ……………. • ……………. • Therefore, # Neutrons = ……………. _____________ _____________ 55 Cs 133 Example 1
- 36. Example 2 If an element :Magnesium a) number of protons b) number of neutrons c) number of electrons d) complete symbol =_____________ = _____________ = _____________ _____________
- 37. Periodic Table
- 38. Metals
- 39. Properties of Metals Metals appear to the left of the dark ziz-zag line on the periodic table. Most metals are solid at room temperature.
- 40. Properties of Metals Metals have luster. This means they are shiny
- 41. Properties of Metals Ductile metals can be drawn into wire.
- 42. Properties of Metals Malleable metals can be hammered into sheets
- 43. Properties of Metals Metals have a high melting point. They are also very dense.
- 45. Nonmetals
- 46. Metalloids They are the elements found along the step like line between metals & non-metals of the periodic table. (Boron “B” – Silicon “Si” – Arsenic “As” – Antimony “Sb” – Tellurium “Te” – Polonium “Po” – Astatine “At”)