1. Section 2 – A Guided Tour of the Periodic Table
Chapter 4 Study Guide

2. Definitions

3. Periodic law:
The law stating that repeating chemical and physical properties of elements change periodically with the atomic numbers of the elements

4. Period:
Horizontal rows of elements K Ca Sc Ti V

5. Group: Vertical columns of elements
Elements in the same group have similar properties Li Na K Rb Cs

6. Ion: Atoms that either lose electrons or gain electrons
Have positive or negative charge

7. Atomic number: The number of Protons an element has
Determines the sequence of the periodic table

8. Mass number: The total number of subatomic particles
Mass # = Protons + Neutrons

9. Isotope: Atoms of an element that have different numbers of neutrons
Carbon-12, Carbon-14

10. Atomic mass unit (amu):
Standard unit of atomic mass, equal to one-twelfth the mass of a Carbon-12 atom

11. Average atomic mass:
A weighted average of the masses of all naturally occurring isotopes. More common isotopes count more than less common ones.

12. Questions?

13. Objecive 1: Relate the organization of the periodic table to the arrangement of electrons in an atom.

14. Objective 1
(1) The order of elements in the periodic table is based on the number of protons in the nucleus.

15. Objective 1
(2) Atoms of elements that are in the same group have the same number of valence electrons.

16. Objective 1
(3) Valence electrons determine an atom’s chemical properties.

17. Objective 1
(4) The periodic table organizes elements into groups that have similar properties.

18. Objective 1
(5) Magnesium (Mg) is located to the right of sodium (Na) because Mg has more electrons and more protons.

19. Objective 1
(6) Elements that have one valence electron tend to be highly reactive, form ions, and become charged.

20. Objective 1
(7) The order of elements in the periodic table is based on the number of protons in the nucleus.

21. Objective 1
(8) Because atoms of elements in the same group of the periodic table have the same number of valence electrons, they have similar properties.

22. Objective 1
(9) The periodic law states that when elements are listed in order of atomic number, similarities in their properties will emerge in a regular pattern.

23. Questions?

24. Objective 2: Explain why some atoms gain or lose electrons to form ions.

25. Objective 2
(10) Ionization refers to the process of losing or gaining electrons.

26. Objective 2
(11) A lithium ion is much less reactive than a lithium atom because it has a full outermost energy level.

27. Objective 2
(12) Some elements are highly reactive because their outermost energy levels are only partially filled.

28. Objective 2
(13) The valence electron of a lithium atom is easily removed to form a lithium ion or cation with a charge of 1+.

29. Questions?

30. Objective 3: Determine how many protons, neutrons, and electrons an atom has, given its symbol, atomic number, and mass number.

31. Objective 3
(14) Oxygen’s atomic number is 8. This means that an oxygen atom has eight protons in its nucleus.

32. Objective 3
(15) An atom’s mass number equals the number of protons plus the number of neutrons.

33. Objective 3
(16) An element’s atomic number is equal to its number of protons.

34. Objective 3
(17) Two different isotopes of an element have different number of neutrons.

35. Objective 3
(18) The mass number of an element that has 19 protons, 19 electrons, and 20 neutrons is = 39.

36. Objective 3
(19) As you move left to right across the periodic table, elements have more protons and higher mass numbers.

37. Objective 3
(20) An iron atom has an atomic mass of 56. Its atomic number is 26. This iron atom has 56 – 26 = 30 neutrons.

38. Objective 3
(21) An atom of potassium has an atomic mass of 39 amu and an atomic number of 19. It therefore has 39 – 19 = 20 neutrons in its nucleus.

39. Questions?

40. Objective 4: Describe how the abundance of isotopes affects an element’s average atomic mass.

41. Objective 4
(22) An element’s average atomic mass is a weighted average, so common isotopes have a greater effect than uncommon ones.

42. Objective 4
(23) An atomic mass unit is equal to one-twelfth the mass of a carbon-12 atom.

43. Objective 4
(24) More abundant isotopes will have more effect on the average atomic mass of an element.

44. Objective 4
(25) An element’s average atomic mass refers to the weighted average of the masses of all of its naturally occurring isotopes.

45. Objective 4
(26) Isotopes of an element have the same atomic number but different atomic mass.

46. Questions?