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CHEMISTRY FORM 2


1. STRUCTURE OF THE ATOM, AND THE PERIODIC TABLE
2. CHEMICAL FAMILIES AND PATTERNS IN PROPERTIES
3. CHEMICAL BONDING AND STRUCTURE
4. SALTS
5. EFFECT OF AN ELECTRIC CURRENT ON SUBSTANCES
6. CARBON AND SOME OF ITS COMPOUNDS
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Structure of the Atom, and the Periodic Table: Development of the Periodic Table

1.0 Structure of the Atom, and the Periodic Table


1.5 Development of the Periodic Table


Questions 1.5(a)

  1. Table 1.5 presents the first 20 elements arranged in the order of atomic number. Complete the table by writing the electronic arrangement for each element.

  2. Table 1.5: The first 20 elements

    high school chemistry, Why electrons don't fall to the nucleus

  3. Atoms with the same number of electrons in their outermost energy levels have similar chemical properties. The same is true with atoms whose outermost energy levels are filled (having the maximum number of electrons they can hold). Which elements are chemically similar to:
    1. Helium (He)
    2. Lithium (Li)
    3. Beryllium (Be)
    4. Boron (B)
    5. Carbon (C)
    6. Nitrogen (N)
    7. Oxygen (O)
    8. Fluorine (F)
    9. Neon (Ne)
  4. As we move down the list of atomic numbers, we come across elements with similar chemical properties, at an interval. Examples are beryllium, magnasium, and calcium. True or false?

Answers to Questions 1.5(a)


Observe a pencast on why the table of elements is called Periodic Table.


(courtesy Youtube-Why table of elements is called Periodic Table by Joseph Rabari)

With elements arranged according to atomic numbers, we repeatedly meet elements with the same number of outermost electrons as we go down the list. Such elements are chemically similar. An example is, moving from lithium to sodium, then potassium which are in the second, third and fourth energy levels (L, to M, N). It follows a pattern or cycle, hence the term periodic. K, L, M, and N correspond to periods.


Questions 1.5(b)

  1. From your answers to Question 1 or 2 of Questions 1.5(a), list in order of atomic number, from left to right the elements in the rows (Periods) shown below.
    high school chemistry

  2. Identify the shortest Period, with the fewest elements. (NB: There are many more elements after calcium.)
  3. From your answers to Question 2 of Questions 1.5(a), list in order of atomic number from top to bottom, chemically similar elements in the Groups I to VIII. Group I is for elements with 1 outermost electron, Group II for elements with 2 outermost electrons, and so on.



Answers to Questions 1.5(b)


If we combine the columns (Groups) of chemically similar elements and rows of the same number of energy levels (Periods), the product is called a Periodic Table. Periodic Table enables us to predict the behavior of a given element from its position in the table. Periods are numbered in Arabic numerals 1 upto 7, and Groups in Roman numbers I upto VIII.


A periodic table is an arrangement of elements according to number of protons and energy levels, from which we can predict physical and chemical properties.


Figure 1.5 Simplified periodic table