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#### Periodic Table Hints

 Posted on August 13, 2012 at 6:35 AM

Everything Periodic Table

1 What are the horizontal rows and vertical column in a periodic table known as?

A: The horizontal rows are called period and the vertical column are called group.

2 What information does the group number of an element tells us?

A: It tells us the number of valence electrons that an atom has. For example, group 1 elements have 1 valence electron and group 7 elements have 7 electrons on the outer shell.

3 What information does the period number of an element tells us?

A: It tells us the number of electrons an atoms has. For example, sodium has an electronic configuration of 2,8,1. It is in period 3 hence it has 3 electron shells.

4 How do metals react and how do non-metals react?

A: Metals react by losing electrons and non-metals react by gaining electron.

5 What are some common physical properties of metals?

A: Metals are ductile (able to be stretched into wires), malleable (able to form and shape easily), good conductors of electricity, good conductors of heat, sonorous (produce a tickling sound when struck), generally high melting and boiling points (except for group 1 metals and mercury which have low melting point).

6 What are the common chemical properties of metals?

A: Metals generally react with acids to form salt and hydrogen gas. They also form ionic compounds when reacted with non-metals. The more reactive metals like the group 1 metals can react with cold water to form aqueous group 1 hydroxide and hydrogen gas.

7 What is the name given to group 1 elements?

A: Group 1 elements are collectively called alkali metals.

8 What are some properties that are unique to group 1 elements only?

A: Group 1 metals are soft metal. Group 1 metals unlike most metals have low melting and boiling point. Group 1 metals can react with water to form a metal hydroxide and hydroxide.

9 Write the word and chemical equations, with state symbol, for sodium's reaction with water.

A: Sodium + water --> sodium hydroxide + hydrogen gas.

2Na(s) + 2H2O(l) --> 2NaOH(aq) + H2(g).

10 Describe the reactions of group 1 metals.

A: Alkali metals react with water to form metal hydroxide and hydrogen gas. They also react with acid to form salt and hydrogen gas. Group 1 metals react with halogens (group 7 element) to form metal halide. For example, sodium reacts with chlorine to form sodium chloride and potassium reacts with bromine to form potassium bromine.

11 What is the name given to elements in group 7?

A. Halogens.

12 What is the name given to elements in group 0?

A: Noble gas.

13 What is the name given to elements between group 2 and 3?

A: Transition metals.

14 How many valence electrons does group 1, group 2 and group 3 elements has?

A. Group 1 has 1, group 2 has 2 and group 3 has 3 valence electrons. (This is the safest way to determine the number of valence electrons, do not do the 2,8,8,8.... it will be wrong).

15 What is the ionic charge expected of group 1, group 2 and group 3 ions?

A: Group 1 ions is +1, group 2 is +2 and group 3 is +3.

16 What are some of the common properties of group 1 metal? (state only properties possessed by group 1 metals.

A: Soft metal, low melting boiling point (as opposed to most metals which are high) and low density.

17 State the trends of properties of group 1 elements down the group.

A: Melting and boiling point decreases down the group, reactivity increases down the group and density increases down the group.

18 Explain VERY briefly why melting point of group 1 metals decreases down the group.

A: The metal bonds holding the positive ions and negative sea of electrons weakens. So lesser energy is needed to overcome the forces of attraction and hence melting and boiling point decreases.

19 Explain in detail why the melting point of group 1 metals decreases down the group.

A: As the metals moved down the group, the atomic radius increases. The force of attraction between the positive nucleus and negative sea of electrons weakens. This weakens the metallic bonds and their melting point will decreases.

20 Explain why reactivity of metals increases down the group.

A: As the metals moved down the group, the atomic radius of the atoms increases. The shielding effect between the positive nucleus and the valence electrons increases. This weakens the force of attraction between the nucleus and the valence electrons. Since the metals react by losing electrons, it is easier to lose electrons down the group hence reactivity increases.

21 Describe a simple experiment to test the reactivity of lithium, sodium and potassium with a water.

A: Add same amount of the 3 metals into 3 separate beakers of water. Ensure all the water is identical and of the same temperature. It will be observed that lithium's reaction with water is fast, sodium is vigorous and potassium is explosive. This shows that potassium is the most reactive of the 3 metals and reactivity of metals increases down the group.

22 Describe what you will observe when sodium is added to water mixed with universal indicator. Explain the changes to the solution.

A: Bubbles of gas (effervescence) observed, gas produced extinguished light splint with a pop sound. Solution changes from green to violet. Water is a neutral substance therefore, it appears green with universal indicator. When sodium reacts with water, it forms sodium hydroxide and hydrogen gas. Since sodium hydroxide is a strong alkali, the universal indicator turns violet.

23 What are the states of the halogens at room temperature?

A: Both chlorine and flourine are gases at room temperature, bromine is a liquid at room temperature, iodine and astatine are both solids at room temperature.

24 What are the type colours of the halogens at room temperature?

A: Flourine is a pale yellow gas, chlorine is a greenish yellow gas, bromine is a reddish brown liquid, iodine is a black solid (sometime it can be BROWN SOLUTION) and astatine is a black solid.

25 State the trends of group 7 substances.

A: The colours of the molecules darkens down the group, the reactivity decreases down the group, the melting boiling point increases down the group.

26 What is a displacement reaction with regards to halogen?

A: A more reactive halogen can displace a less reactive element from its salt.

27 What are the colours of standard solutions?

A: Most of the solutions you will be encountering are colourless solutions. Solutions of group 1 and group 2 salts are all colourless. the coloured solutions are normally from transition metals. Like iron (II) salts are green, copper (II) salts are blue and iron (III) salts are yellow.

28. Describe and explain what happen when bromine is added to potassium chloride.

A: (First off bromine is reddish brown, potassium chloride is a group 1 salt so it is a colourless solution.) There is no visible reaction. Bromine is less reactive than chlorine so it is unable to displace chlorine from its salt.

29. Describe and explain what happen when chlorine is added to potassium bromide.

A: (Again potassium bromide is a group 1 salt so it is a colourless solution and chlorine is greenish yellow) When the greenish yellow gas is added to the colourless solution, solution turns reddish brown. Chlorine is more reactive than bromine hence it is able to displace bromine from potassium bromide. The displaced bromine is reddish brown, causing the solution to turn reddish brown.

30 Write the chemical equation for the reaction in question 29

A: Cl2 + 2KBr --> 2KCl + Br2. Ionic equation: Cl2 + 2Br- --> 2Cl- + Br2

31 Describe and explain what happen when chlorine is added to potassium iodide.

A: When greenish yellow gas is added to colourless solution, solution turns brown. Chlorine is more reactive than iodine so it is able to displace iodine from potassium iodide.

OR

A: When greenish yellow gas is added to colourless solution, black solid appears. Chlorine is more reactive than iodine so it is able displace iodine from potassium iodide.

Categories: Chemistry

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