Periodic Table Past Years

An atom of an element has eight electrons only. Which statement about this element is correct?

• It forms an ion with two negative charges.

• It has a full outer shell of electrons.

• It is a metal.

• It is in Group VIII of the periodic table.

Answer explanation

Element with eight electrons is Oxygen! It is located in Group VII.

Check the charges from the periodic table. Group VII all have -2 charges!

The positions of four elements are shown on the outline of part of the periodic table. Which element is a solid non-metal at r.t.p.?

• A

• B

• C

• D

Answer explanation

In Group VIII, the element that is solid in room temperature (r.t.p) is Iodine.

The Group I metals lithium, sodium and potassium show trends in their melting points and in their reactions with water.

 

Which statement is correct going down the group from lithium to potassium? 

• Their melting points decrease and their reaction with water becomes less vigorous.

• Their melting points decrease and their reaction with water becomes more vigorous.

• Their melting points increase and their reaction with water becomes less vigorous.

• Their melting points increase and their reaction with water becomes more vigorous.

Answer explanation

Trends of Group I alkali metals down the group!

- Melting point decreases

- Elements become more reactive

- They react more vigorously with water

Which is a property of the element molybdenum, ⁹⁶Mo₄₂?

• Low density

• Low melting point

• Forms white or colourless compounds

• Has more than one oxidation state

Answer explanation

Molybdenum is a TRANSITION METAL.

One of the property of transition metal is that it has more than one oxidation state!

An ionic compound has the formula X₃Y_2.

To which groups of the Periodic table do X and Y belong?

• X: Group II

  Y: Group III

• X: Group III

  Y: Group II

• X: Group II

  Y: Group V

• X: Group V

  Y: Group II

Answer explanation

Steps to identify the group: X₃Y₂

Find the charges first! How? Reverse criss-cross

1. X₃Y₂ becomes X² Y³

2. X is a positive ion = X²⁺

3. Y is a negative ion = Y^3-

4. Identify the group with those charges!

The table gives the formulae of the catalysts used in some industrial processes.

How many different transition metals are included, as elements or as compounds, in the list of catalysts?

• 3

• 4

• 5

• 6

Answer explanation

Transition metals are located between group II and group III.

There are 5 total in the table!

- Fe, Mo, V, Ti and Cu

Which one did you missed?

X and Y are diatomic elements. X is less reactive than Y.

What are elements X and Y?

• A

• B

• C

• D

Answer explanation

Group VII elements becomes less reactive DOWN the group.

Thus, Iodine (X) is less reactive than bromine (Y).

Check with your own periodic table!

The positions of four elements are shown on the outline of part of the Periodic Table.

Element X has a high melting point and is a good conductor of electricity.

It forms chlorides XCl₂ and XCl₃.

Which element is X?

• A

• B

• C

• D

Answer explanation

High melting point, good conductor of electricity and more than one oxidation state (XCl₂ and XCl₃).

X must be.. a TRANSITION METAL.

Many properties of an element and its compounds can be predicted from the position of the element in the Periodic Table.

What property could not be predicted in this way?

• The acidic or basic nature of its oxide

• The formula of its oxide

• The number of isotopes it has

• Its metallic or non-metallic properties

Answer explanation

We can identify from periodic table:

1. Metals / non-metals

2. Formula of oxide using charges based on their group

3. Acidic (non-metal oxide) / basic oxide (metal oxide)

But NOT the number of isotopes.

Which statement about the elements chlorine, bromine and iodine is correct?

• They are all gases at room temperature and pressure.

• They are in the same period of the Periodic Table.

• They become darker in colour from chlorine to bromine to iodine.

• They possess one electron in the outermost shell.

Answer explanation

One of the trend of Group VII elements is that the elements becomes DARKER down the group!