01. Electron Theory

Question 1. A neutron has.


A. the opposite charge to an Electron but half the weight of a proton.


B. the same charge as an Electron but half the mass.


C. no electrical charge but will add weight to the nucleus.


Answer . no electrical charge but will add weight to the nucleus.







Question 2. The unit which consists of two or more different types of atoms is known as a.


A. particle of an element.


B. molecule of a compound.


C. molecule of an element.


Answer . molecule of a compound.










Question 3. In what equipment is a photon radiated when an electron leaves a hole?.


A. Photo-cell.


B. LED.


C. Photo diode.


Answer . LED.










Question 4. A good electrical insulating material will contain.


A. Only a small number of electrons in the outer shell of each atom of the material.


B. strongly bound electrons in the atoms of the material.


C. Weakly bound 'free' electrons in the atoms of the material.


Answer . strongly bound electrons in the atoms of the material.










Question 5. The smallest particle that a substance can be split and show the same properties as the whole is known as.


A. an Element.


B. a Molecule.


C. an Atom.


Answer . an Atom.










Question 6. What charge does the nucleus of an atom possess?.


A. Positive.


B. Neutral.


C. Negative.


Answer . Positive.










Question 7. What is the maximum number of electrons in shell N of an atom?.


A. 18.


B. 32.


C. 16.


Answer . 32.


Explanation. Shell k = 2 electrons, shell L= 8 electrons, shell M = 18 electrons and shell N = 32 electrons (or use the 2n2 exclusion rule).






Question 8. An oxygen molecule is made up of.


A. two oxygen atoms sharing neutrons.


B. two oxygen atoms sharing protons.


C. two oxygen atoms sharing electrons.


Answer . two oxygen atoms sharing electrons.










Question 9. If electrons are added to an atom it becomes.


A. a neutral ion.


B. a positive ion.


C. a negative ion.


Answer . a negative ion.










Question 10. An element whose atoms have fewer than 4 electrons in their valency shell are.


A. semiconductors.


B. good insulators.


C. good conductors.


Answer . good conductors.


Explanation. The further away from a 'complete' shell the better a conductor it is.






Question 11. The charge on a proton is.


A. positive.


B. negative.


C. neutral.


Answer . positive.










Question 12. What effect do the electrons of one atom have upon the electrons of another atom?.


A. They have no effect on each other.


B. They repel each other.


C. They attract each other.


Answer . They repel each other.










Question 13. What is a molecule?.


A. The smallest part of an atom.


B. The smallest part of a compound.


C. The smallest part of an electron.


Answer . The smallest part of a compound.










Question 14. An atom is.


A. the smallest part of an element that retains its characteristics.


B. the smallest part of a compound that can exist independently.


C. the smallest particle of matter.


Answer . the smallest part of an element that retains its characteristics










Question 15. A neutron is a particle which is.


A. is contained in the nucleus of all atoms.


B. orbits the nucleus of the atom.


C. is contained within the nucleus of most atoms.


Answer . is contained within the nucleus of most atoms.


Explanation. Most atoms' because hydrogen has no neutron.






Question 16. The mass of an atom is contained mainly in the.


A. proton.


B. nucleus.


C. electron.


Answer . nucleus.


Explanation. The proton and the neutron are approximately the same mass (neutron very slightly heavier). The electron is just under 1/2000th of a proton or neutron.






Question 17. When an atom loses or gains an electron it is called.


A. a molecule.


B. a current.


C. an ion.


Answer . an ion.










Question 18. A good electrical insulator is a material which.


A. contains a large number of positive ions.


B. has its electrons tightly bound to their parent atoms.


C. has more protons than electrons.


Answer . has its electrons tightly bound to their parent atoms.










Question 19. An electric current is.


A. an ordered flow of electrons.


B. a surplus of free electron.


C. an excitement of electrons in a metal.


Answer . an ordered flow of electrons.










Question 20. An atom contains.


A. hydrogen.


B. molecules.


C. electrons.


Answer . electrons.










Question 21. Germanium and silicon have how many electrons in their outer shell?.


A. 6.


B. 4.


C. 2.


Answer . 4.


Explanation. All semiconductors (including carbon) has 4 electrons in their outer shell.






Question 22. If a free electron is given to another atom, that atom is a.


A. valency atom.


B. negative ion.


C. positive ion.


Answer . negative ion.


Explanation. That atom will be negatively charged due to the additional electron.






Question 23. The atomic number of an atom is determined by the number of.


A. protons.


B. electrons.


C. neutrons.


Answer . protons.


Explanation. Atomic number = number of protons. Mass number = number of protons + neutrons.






Question 24. The valence electron is.


A. the electron in outer shell of atom.


B. the electron in inner shell of atom.


C. a positive electron.


Answer . the electron in outer shell of atom.


Explanation. The valence electrons is/are in the outer shell.






Question 25. An atom with a deficiency in electrons has.


A. low resistance.


B. high resistance.


C. high impedance.


Answer . low resistance.


Explanation. An atom with a deficiency of electrons will be positively charged and able to accept electrons freely. Module 4 theory of holes as majority carriers.






Question 26. An atom with less than 4 electrons in its outer shell has.


A. low electrical resistance.


B. no electrical resistance.


C. high electrical resistance.


Answer . low electrical resistance.


Explanation. Low electrical resistance, i.e. a good conductor.






Question 27. Elements such as phosphorus with 5 electrons in their outer shell, when combined with pure silicon, is a.


A. isotopic.


B. acceptor.


C. donor.


Answer . donor.


Explanation. Phosphorus 'donates' an electron to the silicon crystal structure.






Question 28. An hydrogen atom consist of a.


A. Proton, Neutron and an Electron.


B. Proton and an Electron only.


C. Neutron and a proton only.


Answer . Proton and an Electron only.


Explanation. Hydrogen has no Neutron.






Question 29. For an atom to become a negative ion it must.


A. gain at least one electron.


B. have undergone ionisation by the sun.


C. lose at least one electron.


Answer . gain at least one electron.


Explanation. Gaining at least one electron produces a negative ion.






Question 30. What is the maximum number of electrons in shell M of an atom?.


A. 18.


B. 6.


C. 16.


Answer . 18.


Explanation. Use Pauli's exclusion formula. M is the 3rd shell (n=3). 2*3*3 = 18.






Question 31. A neutral atom with an atomic no. of 3 has how many electrons?.


A. 1.


B. 3.


C. Dependant on type of atom.


Answer . 3.


Explanation. Atomic number = number of protons = number of electrons.






Question 32. The nucleus of an atom is.


A. neutral.


B. positive charged.


C. negative charged.


Answer . positive charged.


Explanation. Nucleus is positively charged.






Question 33. Electron orbits are called.


A. waves.


B. shells.


C. valences.


Answer . shells.


Explanation. shells, or energy levels.






Question 34. A neutral atom gains electrons.


A. It gains a positive charge.


B. It gains a negative charge.


C. It remains neutral.


Answer . It gains a negative charge.










Question 35. An oxygen atom has.


A. protons and electrons.


B. neutrons and protons.


C. protons, neutrons and electrons.


Answer . protons, neutrons and electrons.

Explanation. Jepperson, A+P Technician General Handbook, Chapter 2 Matter and Energy.