WAEC Chemistry Past Questions & Answers - Page 120

596.

Which of the following elements is a metalloid?

A.

Carbon

B.

Oxygen

C.

Silicon

D.

Sodium

Correct answer is C

Some examples of metalloids include boron, silicon, germanium, arsenic etc.

597.

Which of the following statements about a radioactive substance is/are correct? l. lt emits radiation continuously and spontaneously. ll. The emitted radiations are affected by temperature and pressure III. The radiation can penetrate opaque matter

A.

ll only

B.

l and ll only

C.

l and lll only

D.

ll and lll only

Correct answer is C

The properties of radioactive elements holds true except that radioactive decay is not dependent on external conditions except electron capture and bombarding the radioactive material with subatomic particles.

598.

The d-block elements are paramagnetic because they

A.

contain paired electrons which are repelled by magnetic field

B.

contain unpaired electrons in the partially filled 3d-orbital

C.

contain paired electrons which are repelled by magnetic field force

D.

have delocalized valence electrons

Correct answer is B

Paramagnetism is a characteristic possessed by an atom with an unpaired electron. 

599.

Two elements, X and Y are in the same group on the periodic table because they both have the same

A.

number of electronic shells

B.

number of valence electrons

C.

atomic size

D.

atomic number

Correct answer is B

The members of the same group always have the same number of electrons in the outer shell (i.e number of valence electrons).

600.

The atomic radii of metals are usually

A.

greater than their ionic radii

B.

equal to their ionic radii

C.

less than their ionic radii

D.

less than those of non-metals in the same period

Correct answer is A

Metals give off electrons. This means that atomic radius is always greater than the ionic radius for metals.