Electronics

1. Electronics The Nature of Matter

2. Presentation Overview • Terms and Definitions • Atom Models • Electrons and Electron Shells • Random Drift of Electrons • Law of Electrical Charges

3. Terms and Definitions • Matter- A material substance that occupies space and has mass; can be solid, liquid, or gas • Atom- A basic unit of matter consisting of a dense nucleus surrounded by a cloud of electrons • Element- Matter composed of atoms having the same number of protons in the nucleus • Compound- Substance consisting of two or more elements joined by chemical bonds • Molecule- Stable combination of two or more atoms

4. Terms and Definitions (continued) • Mixture- A substance made by combining two or more materials that are not joined chemically • Charge- A basic property of matter • Electron- A subatomic particle with a negative electric charge • Proton- Positively charged subatomic particle— generally located in the nucleus • Neutron- Subatomic particle with no charge— generally located in the nucleus • Ion- An electrically charged atom where the number of protons does not equal the number of electrons

5. Atoms • Fundamental units of matter. • Consists of a nucleus having at least one proton and usually one or more neutrons, with a number of electrons bound to the nucleus through electrical attraction. • Atoms are the simplest forms of an element that still have the unique characteristics of that element.

6. Atomic Particles Classical image Bohr model Modern image Cloud model

7. Elements and Compounds • Matter is anything that occupies space or has mass. • An elementis a substance consisting of atoms that have the same number of protons in the nucleus. • Compounds are mixtures or combinations of two or more elements.

8. How Does This Relate to Electricity? • Electricity and electronics relates to the behavior of electrons. • Electricity relates to the buildup and flow of electrons. • Electronics relates to the control of electricity by specialized devices. • Transistors and integrated circuits • To understand electricity and electronics, we need to understand more about electrons.

9. Electrons • Electrons orbit the nucleus of an atom. • The total number of electrons is generally equal to the number of protons. • Electrons arrange themselves into layers. • These layers are called shells or orbitals. • Each shell contains one or more electrons. • The number of electrons in each shell follows a formula Ne = 2n2.

10. Inner and Outer Orbits • When these are inner orbits of an atom, they contain electrons up to their maximum count and contain no free electrons. • Orbit #1- can contain two electrons maximum • Orbit #2- can contain eight electrons maximum • Orbit #3- can contain 18 electrons maximum • The maximum number of electrons in the outer orbit is eight. • The outer orbit of the atom is an orbit that may be partially filled or contain free electrons.

12. Electron Shells • Electrons are attracted to protons. • Electrons in inner shells are closer to the nucleus. • Electrons in inner shells have low energy. • Electrons in outer shells have more energy. • Inner shell electrons are strongly attracted to the nucleus. • These electrons are considered bound. • They never gain enough energy to leave the atom. • They are never shared between atoms.

13. Valence Electrons • Only outer shell electrons are important to electricity and chemistry. • They can be shared and form bonds. • The outer shell is called the valence shell. • Electrons in this shell are called valence electrons. • Electrons in the outer shell can gain enough energy to completely leave the atom. • These electrons become free.

14. Free Electrons • Free electrons are important to electricity. • They can move and be used to build up charge or create current. • Materials without free electrons cannot create or conduct electricity. • These materials can be insulators. • The best conductors are those with only one electron in the outer shell. • Gold, silver, copper

15. Periodic Table of the Elements • The Periodic Table of the Elements is arranged by atomic number. • The atomic number of an element refers to the number of protons that make up an atom of the element. • The number of electrons generally equals the number of protons. • Groups of elements read in a vertical column up and down. • Elements in a group have the same number of outer shell electrons.

17. Periodic Table of the Elements (continued) • Reading across in a row, the number of protons in the nucleus increases by one. • Because the number of electrons in an atom is generally equal to the number of protons, different elements can have different numbers of electrons in their valence shell. • Atoms without the same number of electrons and protons can exist and are called ions. • Elements with the same number of valence electrons are similar electrically and chemically. • They can be grouped together.

18. Free Electrons • Electrons are bound to the nucleus because of electrostatic forces of attraction between positive protons in the nucleus and negative electrons orbiting the nucleus. • Inner shell electrons are strongly bound. • The outer shell electrons in conductors are weakly bound. • Room temperature heat energy is enough to allow them to become free electrons.

19. Conductors • Good conductors generally have one or two electrons in the outer shell. • Aluminum is a good conductor with three electrons in its outer shell. • The number of inner shell electrons nearly balances the number of protons. • This creates a charge layer that shields the outer shell electrons. • They do not feel the same attraction force the inner electrons do.

20. Metals • Metals are good conductors because they generally have two electrons in the outer shell. • Metals start with Row 4. • Going across the row, each element has one additional proton in the nucleus. • Each additional electron needed to balance the charge goes into an inner shell. • Atoms can only have more than eight electrons in a shell for an inner shell. • The number of outer shell electrons stays at two.

21. Row 4 Metals • Row 4 means four layers (shells) of electrons. • The number of electrons in each shell follows the formula- Ne = 2n2. • The third layer can have 18 electrons. • But, the outer shell of an atom can only have a maximum of eight electrons. • We only start to get more than eight electrons in the third shell after an atom has a fourth shell.

22. Electron Shells Nucleus

23. 4 Shell Number 3 2 1

24. 32 Maximum number of electrons in each shell. 18 8 2

25. 32 32 electrons in the fourth shell. 18 8 2

26. 8 But only eight electrons if any shell is the outer shell. 18 8 2

27. The third shell can only have eight electrons if it is an outer shell. 8 8 2

28. 2 It can have 18 electrons only when there is a fourth shell. 18 8 2

29. Good Conductors • Note the column that has Cu, Ag, and Au. • Copper, silver, gold • Each of these metals has one electron in its outer shell. • Other metals in each row have two electrons in the outer shell. • This is because atoms are more stable when each electron shell is “full.” • Consider the inert gasses.

30. Copper • Copper is the first element to be able to have a full third shell with 18 electrons. • Remember there must be a fourth shell to be able to get 18 electrons in the third shell. • Copper has the following number of electrons in each shell: 1, 2; 2,8; 3,18; 4,1 • 2 + 8 + 18 + 1 = 29, which is the atomic number for copper. Key: shell, # of electrons

31. Slides 32-40 are pictures showing the electrons in each shell from atomic numbers 19 to 31.

32. Potassium (K) 1 8 19 electrons 8 2 19 protons

33. Calcium (Ca) 2 8 20 electrons 8 2 20 protons

34. Scandium (Sc) 2 9 21 electrons 8 The next electron goes into the third shell. 2 21 protons

35. Skip from Scandium to Nickel. Each extra electron goes into the third shell. Nickel (Ni) 2 16 28 electrons 8 The next electron goes into the third shell. 2 28 protons

36. Copper (Cu) 1 18 29 electrons 8 2 29 protons

37. Copper (Cu) 1 18 29 electrons One outer shell electron. 8 2 29 protons

38. Copper (Cu) 1 18 29 electrons Note this full third shell. 8 2 29 protons

39. Zink (Zn) 2 18 30 electrons 8 2 30 protons

40. Gallium (Ga) 3 18 31 electrons 8 2 31 protons

41. Presentation Summary • Terms and Definitions • Atom Models • Electrons and Electron Shells • Random Drift of Electrons • Law of Electrical Charges