WAEC Chemistry Past Questions & Answers - Page 157

781.

Which of the following statements is not true of halogens?

A.

they exist in different physical states

B.

they exist as diatomic molecules

C.

their ionic radii decrease down the group

D.

their melting and bolling points increase down the group

Correct answer is C

No explanation has been provided for this answer.

782.

Atom \(^{234} _{88} Q\) decay by alpha emission to give an atom R. The atomic number and mass number of atom R are respectively

A.

86 and 230

B.

87 and 234

C.

88 and 233

D.

90 and 238

Correct answer is A

\(^{234} _{88} Q \to R + ^4 _2 He\)

\(\therefore R = ^{234 - 4} _{88 - 2} R\)

= \(^{230} _{86} R\)

783.

What is the atomic number of an element whose cation Y+ has the electronic configuration 1s22s22p6?

A.

9

B.

10

C.

11

D.

12

Correct answer is C

No explanation has been provided for this answer.

784.

The valence electrons in a chloride ion are [17CI]

A.

2p electrons only

B.

3s and 3p electrons only

C.

3p and 3d electrons only

D.

3p electrons only

Correct answer is B

No explanation has been provided for this answer.

785.

Find the number of neutrons in an atom represented by 4521X.

A.

21

B.

24

C.

45

D.

66

Correct answer is B

No explanation has been provided for this answer.