HW From textbook “CHEMISTRY a Contemporary Approach”

Read "Period 1,2,3,4" p177&178

Do Questions 3,11,15,24 p178-181

Elements can be differentiated by chemical properties (how an element behaves during a chemical reaction).  In groups 1, 2, and 13-18  elements within the same group have the same number of valence electrons (helium is an exception) and therefore similar chemical properties.  

The chemical properties of elements in group 1 (the alkali metals) are:

• They are the most reactive metals therefore they are always found in compounds in nature. Reactivity increases as atomic number increases, due to a lower IE (ionization energy).

• They react with elements in group 17 to give the general formula MX (M is the metal and X represents any members of group 17. 

  M + X --> MX

  Example

  Na + Cl  --> NaCl

The chemical properties of elements in group 2 (the alkaline earth metals) are:

• They occur in nature only in compounds because of their high reactivity. They are less reactive than group 1 elements due to higher IE.

• They react with elements in group 17 to give the general formula MX₂ (M is the metal and X represents any members of group 17. 

  M + X₂ --> MX₂

  Example

  Mg + Br₂  --> MgBr₂

The chemical properties of elements in group 3-12 (the transition elements) are:

• Many transition elements and their aqueous solutions are brightly colored such as Cr (chromium), Cu (copper) and Ni (nickel).

  Example

  The aqueous solution of CuSO₄ is blue.

The chemical properties of elements in group 17 (the halogens) are:

• It is the only group that contains all three phases of matter.

• They occur in nature only in compounds because of their high reactivity. Reactivity decreases as atomic number increases due to lower electronegativities.

The chemical properties of elements in group18 (the noble gases) are:

• They are all monatomic gases with 8 valence e- except for He with 2 valence e-. Therefore, they are very stable and relatively inert, except for Kr, Xe, and Rn.

  Example

  Compounds such as KrF₄, XeF₄, and RnF₄ have been produced in laboratories.

Some elements exist in two or more forms in the same phase (allotropes). These forms differ in their molecular or crystal structure, and hence in their properties.

Example 1

Oxygen, O₂ (g) and ozone, O₃ (g) are allotropes.

Example 2

Diamond, graphite, and  buckminsterfullerene (large symmetrical molecules that contain 60 or more carbon atoms) are allotropes.

TEST YOUR UNDERSTANDING

1/07

31 When the elements in Group 1 are considered in order from top to bottom, each successive element at standard pressure has

(1) a higher melting point and a higher boiling point         (2) a higher melting point and a lower boiling point

(3) a lower melting point and a higher boiling point           (4) a lower melting point and a lower boiling point

33 At STP, which list of elements contains a solid, a liquid, and a gas? (1) Hf, Hg, He (2) Cr, Cl2, C (3) Ba, Br2, B (4) Se, Sn, Sr

34 Element X reacts with iron to form two different compounds with the formulas FeX and Fe2X3. To which group on the Periodic Table does element X belong?      (1) Group 8 (2) Group 2 (3) Group 13 (4) Group 16

6/07

Base your answers to questions 73 through 76 on the information below.

The table below lists physical and chemical properties of six elements at standard pressure that correspond to known elements on the Periodic Table. The elements are identified by the code letters, D, E, G, J, L, and Q

.

73 What is the total number of elements in the “Properties of Six Elements at Standard Pressure” table that are solids at STP?

74 An atom of element G is in the ground state. What is the total number of valence electrons in this atom?

75 Letter Z corresponds to an element on the Periodic Table other than the six listed elements. Elements G, Q, L, and Z are in the same group on the Periodic Table, as shown in the diagram below.

Based on the trend in the melting points for elements G, Q, and L listed in the “Properties of Six Elements at Standard Pressure” table, estimate the melting point of element Z, in degrees Celsius.

76 Identify, by code letter, the element that is a noble gas in the “Properties of Six Elements at Standard Pressure” table.

8/07

6 The carbon atoms in graphite and the carbon atoms in diamond have different  (1) atomic numbers     (2) atomic masses     (3) electronegativities     (4) structural arrangements

8 Which statement describes a chemical property of the element magnesium?

        (1) Magnesium is malleable.         (2) Magnesium conducts electricity.         (3) Magnesium reacts with an acid.         (4) Magnesium has a high boiling point.

38 Which group on the Periodic Table of the Elements contains elements that react with oxygen to form compounds with the general formula X₂O?    (1) Group 1 (2) Group 2 (3) Group 14 (4) Group 18

6/06

8/06

1/05

32 An unknown element X can form a compound with the formula XBr₃. In which group on the Periodic Table would element X be found?   (1) 1       (2) 2      (3) 13        (4) 14

5 Which element has chemical properties that are most similar to the chemical properties of sodium? (1) Mg (2) K (3) Se (4) Cl

6/04

62 Based on the Periodic Table, explain why Na and K have similar chemical properties.

8/04

51 In the 19th century, Dmitri Mendeleev predicted the existence of a then unknown element X with a mass of 68. He also predicted that an oxide of X would have the formula X₂O₃. On the modern Periodic Table, what is the group number and period number of element X?

6/02

Which element is classified as a noble gas at STP? (1) hydrogen        (2) oxygen         (3) neon       (4) nitrogen

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