WAEC Past Questions and Answers - Page 1425

7,121.

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.

7,122.

Which of the following ions has an electron configuration different from the other?

A.

17CI-

B.

8O2-

C.

12Mg2+

D.

13AI3+

Correct answer is A

\(_{17}\)Cl\(^-\) = 18 electrons = 2, 8, 8

\(_{12}\)Mg\(^{2+}\), \(_{8}\)O\(^{2-}\) and \(_{13}\)Al\(^{3+}\) all have 10 electrons = 2, 8.

7,123.

Which of the following electron configurations represents that of an atom in its ground state?

A.

1s 22s12p1

B.

1s22s22p63s13p1

C.

1s22s12p3

D.

1s22s22p63s0

Correct answer is D

The ground state of an electron, the energy level it normally occupies, is the state of lowest energy for that electron.

7,124.

The number of orbitals in a p-sub level of an atom is

A.

2

B.

3

C.

5

D.

6

Correct answer is B

The p- orbital has 3 subshells; P\(_x\), P\(_y\) and P\(_z\) subshells.

7,125.

Which of the following statements about thermoplastic material is correct? They

A.

do not melt on heating

B.

harden on heating

C.

decompose on heating

D.

soften and melt on heating

Correct answer is D

No explanation has been provided for this answer.