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WAEC questions for "Chemistry :: Structure of Atom"
Q1

Which of the following scientist discovered the neutron?

A

Ernest Rutherford

B

J.J Thompson

C

James Chadwick

D

R. A Millikan

E
Q2

How many protons does the below element contain?

40  
  Ca
20  

A

20

B

30

C

40

D

60

E
Q3

If 100 atoms of element X contains 70 atmos of 9X and 30 atoms of 11X, Calculate the relative atomic mass of X

A

9.6

B

10.6

C

11.6

D

20.0

E
Q4

How many orbitals are associated with th p-sub energy level?

A

2

B

3

C

5

D

6

E
Q5

Which of the following elements has the electronic configuration: 1s22s22p63s23p1? [11Na, 13Al, 14N, 16S ]

A

Al

B

Na

C

N

D

S

E
Q6

Which of the following ions is isoelectronic with neon? [3Li, 9F, 10Ne, 17Cl, 19K]

A

Cl-

B

F-

C

K+

D

Li+

E
Q7

Which of the following statements about the behaviour of the atom is correct?

A

Atomic size decreases down the group

B

Atomic size increases along the period

C

Anions are smaller than the parent atom

D

Cations are smaller than the parent atom

E
Q8

The mass spectrometer can be used to measure mass of

A

an atom

B

an electron

C

a proton

D

a neutron

E
Q9

Find the number of neutrons in an atom represented by
45  
  X
21  

A

21

B

24

C

45

D

66

E
Q10

The valence electrons in a chloride ions are [17cl]

A

2p electrons only

B

3s and 3p electrons only

C

3p and 3d electrons only

D

3p electrons only

E
Q11

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

A

9

B

10

C

11

D

12

E
Q12

Atom below 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

E
Q13

Consider the following elements and their electronic configuration: W: 1s22s2, X:1s22s22p6 , Y:1s22s22p63s2 Z:1s22s22p63s23p2

Which of the element belong to the same group in the Periodic table?

A

W and X only

B

Y and Z only

C

W and Y only

D

W, Y and Z only

E
Q14

When sodium atom forms the ion Na+,

A

It gains one electron

B

It gains one proton

C

It achieves a noble gas configuration

D

Its diatomic number increases

E
Q15

Which of the following statements about rare gases are correct?

I   Their outermost shells are fully filled

II  They are generally unreactive

III Their outermost shells are partially filled

IV  They have lone pair of electrons in their outermost shell

A

I and II only

B

II and III only

C

I, II and III only

D

I, II, III and IV

E
Q16

How many electron are in then ions F-? [F]

A

8

B

9

C

10

D

19

E
Q17

What is the value of X in the following nuclear reaction? B+ → CfLr + 3n

A

241

B

259

C

261

D

265

E
Q18

In which of the following atoms is the ionic radius larger than the atomic radius? [11Na, 12Mg, 13Al, 17Cl]

A

Aluminium

B

Chlorine

C

Magnesium

D

Sodium

E
Q19
How many orbitals are in the d-sub shell?
A
1
B
3
C
5
D
7
E
Q20
An element X has an isotopic mass of 6 and 7. If the relative abundance is 1 to 12.5 respectively, what is the relative atomic mass of X?
A
6.0
B
6.1
C
6.9
D
7.0
E
Q21

An atom as shown below decays by alpha particle emissions to give an atom Y.

238  
  X
93  
The atomic number and mass number of Y are

 

A

90 and 234 respectively

B

91 and 238 respectively

C

92 and 236 respectively

D

93 and 238 respectively

E
Q22

An element with mass number 133 and atomic number 55 has

A

55 electrons and 55 neutrons

B

55 electrons and 78 neutrons

C

78 electrons and 78 neutrons

D

78 electrons and 55 neutrons

E
Q23

Which of the following pairs of species contains the same number of electron? [6C, 8C, 10Ne, 11Na, 12Mg, 13Al, 17Cl]

A

Mg2+ and Al3+

B

Cl- and Ne

C

Na+ and Mg

D

C and O2-

E
Q24

An element X has electronic configuration 1s2 2s2 2p6 3s2 3p6 4s. To which group in the periodic table does X belong?

A

I

B

II

C

III

D

IV

E
Q25

Which of the following sets of element is arranged in order increasing first ionization energies?

A

11Na, 3Li, 19K, 37Rb

B

37Rb, 19K, 3Li, 11Na

C

3Li, 19K, 11Na, 37Rb

D

37Rb, 19K, 11Na, 3LI

E
Q26
The presence of unpaired electrons in an atom of a d-block element accounts for its
A
ductility
B
lustre
C
malleability
D
paramagnetic
E
Q27

The electronic configuration of an element X is 1s22s22p63s23p4. It can be deduced that X

A

belongs to group 6 of the periodic table

B

belongs to period IV of the periodic table

C

has 3 unpaired electrons in its atom

D

has relative molecular mass of 16

E
Q28

What is the mass number of an element having 20 neutrons, 15 protons and 15 electrons?

A

15

B

30

C

35

D

50

E
Q29
Which of the following changes is charateristics of an alpha particle emission?
A
The nucleus loses two protons and two neutrons
B
A proton combines with an electron giving off heat
C
The nucleus splits into two equal parts
D
Four neuetrons are lost
E
Q30
An element X has an atomic number of 16. What is its most likely oxidation state in its binary compound?
A
-3
B
-2
C
+2
D
+4
E
Q31

Consider the table below:

Element Electronic Configuration
J 2,3
K 2,8,2
L 2,8,3
M 2,8,4
Which pair of elements are in the same group in the Periodic table?

A

J and K

B

K and L

C

J and L

D

K and M

E
Q32

An element which can exist in two or more forms in the physical state, exhibits

A

isotopy

B

structural isomerism

C

allotropy

D

varible valency

E
Q33

The mass of an element is 27 and its atomic number is 13. What is the composition of the nucleus of its atom?

A

13 electrons and 14 protons

B

13 neutrons and 14 protons

C

13 protons and 14 neutrons

D

13 electrons and 14 neutrons

E
Q34

If an atom is represented as shown below, which of the following deductions are correct?
39  
  X
19  

A

It contains 20 protons

B

It forms a covalent chloride

C

Its atomic number is 39

D

Its an alkali metal

E
Q35

Two elements X and Y combine to form a compound formular X2Y3. Which of the following representation would fi the configuration of X and Y?

  X Y
A 2,2 2,3
B 2,6 2,5
C 2,8,3 2,8,3
D 2,8,3 2,6

A

2,2  2,3

B

2,6  2,5

C

2,8,2   2,8,3

D

2,8,3  2,6

E
Q36

Which of the following electrons transitions results in the emission of energy?

A

3p to 3s

B

3p to 4p

C

2s to 2p

D

1s to 2s

E
Q37

Which of the following equipment is not used to do radioactivity?

A

Wilson cloud chamber

B

Geiger-Muller counter

C

Mass spectrometer

D

Photographic plate

E
Q38

The electronic configuration of an element is 1s22s22p63s23p3 . Where is the element located in the periodic table?

A

Group III, period 3

B

Group III, period 5

C

Group V, period 3

D

Group V, period 5

E
Q39

The electrons that are most easily removed from the below element are in which orbital?

24  
  Mg
12  

A

1s

B

2s

C

2p

D

3s

E
Q40

If the relative molecular mass of an element is not a whole number, it can be deduced that the element is

A

naturally radioactive

B

abundant in nature

C

a transition metal

D

an isotopic mixture

E
Q41

The atom of an element X is represented by as X. The basic properties of X depend on the value of

A

Y

B

Z

C

y - Z

D

Z - Y

E
Q42
The atomic number of chlorine is 17. What is the number of electron in a chloride ion?
A
16
B
17
C
18
D
19
E
Q43
A hydrogen which has lost an electron contains
A
one proton only
B
one neutron only
C
one proton and one neutron
D
one proton, one electron and one neutron
E
Q44
Which of the following elements has a ground state configuration with an incomplete penultimate shell?
A
Iron
B
Sodium
C
Aluminum
D
Calcium
E
Q45

The conclusion from Rutherford's Alpha scattering experiment is that

A

atoms are mostly empty space with a small nucleus

B

emissions from radioactive substances consist of three main components

C

there is a nuclear pull on the orbital electrons

D

electrons are deflected by both magnetic and electric fields

E
Q46

Which of the letters indicate elements which exist as diatomic gases?

A

W and Z

B

M and J

C

M and Y

D

Y and Q

E
Q47

Which of the following pairs of letters denotes elements containing the same number of electrons in their outermost shells?

A

J and X

B

M and Q

C

W and Z

D

W and Y

E
Q48
Allotropes of an elements differ in their
A
physical properties
B
chemical properties
C
mass number
D
electronic configuration
E
Q49
What is the mass number of an element if its atoms contain 10 protons, 10 electrons and 12 neutrons?
A
32
B
22
C
20
D
10
E
Q50

Given that the electronic configuration of an element X is 1s22s22p63s23p4, it can be deduced that X

A

belongs to group VI in the Periodic Table

B

belongs to period 4 in the periodic table

C

contains 3 unpaired electrons in the ground state

D

has atomic number 27

E
Q51

A sheet of paper is placed in the path of a beam from a radioactive source. The emissions that pass through the paper consist of

A

alpha particles and gamma rays

B

alpha and beta particles

C

beta particles and gamma rays

D

alpha particles only

E
Q52

Which of the following features of a human skeleton can be determined by carbon-dating?

A

Height

B

Mass

C

Age

D

Race

E
Q53

The atoms of four elements are represented as 20Q 16R 10and 8T. Which of the elements would be unreactive?

A

Q

B

R

C

S

D

T

E
Q54

Chlorine atoms forms Cl- by

A

losing one electron

B

sharing one electron

C

donating one pair of electron

D

gaining one electron

E
Q55

An element Z has a combining power of 3. Which of the following formulae is correct of its compound?

A

ZSO3

B

Z3Cl2

C

Z2O3

D

ZS3

E
Q56

A radioactive solid is best stored

A

under paraffin oil

B

under ultraviolet light

C

in cool, dark cupboard

D

in a box lined with lead

E
Q57

Which of the following atoms contains the highest number of electrons in the outermost shell?

A

8o

B

10Ne

C

15p

D

19k

E
Q58

Pauli Exclusion Principle is related to

A

quantum numbers of electron

B

reversibility of equilibrium reactions

C

electronegativity values of elements

D

collision theory of reaction rates

E
Q59

Which of the orbitals 4s, 4p, 4d and 4p has the lowest energy?

A

4f

B

4p

C

4d

D

4s

E
Q60

Which of the following has neither mass nor charge?

A

Alpha particles

B

Deuterium

C

Gamma rays

D

Neutron

E