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Valency – Quiz 1
Valency Quiz 1 (30 MCQs)
This multiple-choice question set evaluates the understanding of atomic composition, electron configuration, and valency rules in chemical bonding. It covers concepts such as oxidation states, ionic charges, and combining powers of elements, essential for grasping atomic structure and periodic trends.
Quiz Instructions
Select an option to see the correct answer instantly.
1.
What is the valency of Aluminium?
Show Answer
Explanations:
Aluminium, like other Group 13 elements in the periodic table (such as boron), typically forms compounds by losing three electrons to achieve a stable electron configuration similar to that of a noble gas. This means aluminium has a valency of 3.
Option Analysis:
Option A:
Incorrect. Aluminium does not commonly form monovalent ions.
Option B:
Correct. Aluminium forms trivalent ions, making its valency 3.
Option C:
Incorrect. Aluminium does not typically have a tetravalent state in most of its compounds.
Option D:
Incorrect. Aluminium's common oxidation state is +3, not +2.
2.
What is the atomic weight of water?
A) 44 amu.
B) 100 amu.
C) 17 amu.
D) 18 amu.
Show Answer
Explanations:
The atomic weight of water (H
2
O) is calculated by adding the atomic weights of its constituent atoms: two hydrogen atoms and one oxygen atom. Hydrogen has an atomic weight of approximately 1 amu, and oxygen has an atomic weight of approximately 16 amu. Therefore, the total atomic weight of water is (2 × 1) + 16 = 18 amu.
Option Analysis:
Option A:
Incorrect. The sum of hydrogen and oxygen atomic weights does not equal 44 amu.
Option B:
Incorrect. This value is much higher than the actual atomic weight of water.
Option C:
Incorrect. Oxygen's contribution alone (16 amu) plus a hydrogen atom (1 amu) makes 17 amu, not 17 amu for water.
Option D:
Correct. This is the accurate atomic weight of water based on the sum of its constituent elements' weights.
3.
What are valence electrons?
A) Electrons that are involved in thermal conductivity.
B) Valence electrons are the electrons in the outermost shell of an atom that are involved in chemical bonding.
C) Electrons that are only found in the nucleus of an atom.
D) Electrons that are responsible for the mass of an atom.
Show Answer
Explanations:
Valence electrons are the electrons in the outermost shell of an atom that are involved in chemical bonding. This is correct because these electrons determine how atoms interact with each other, forming bonds through sharing or transferring these valence electrons.
Option Analysis:
Option A:
Incorrect. Valence electrons do not involve thermal conductivity; this property is related to the movement of free electrons in metals.
Option B:
Correct as stated above.
Option C:
Incorrect. Valence electrons are not confined to the nucleus but occupy the outermost shell.
Option D:
Incorrect. The mass of an atom is determined by protons and neutrons, not valence electrons.
4.
What is the valency of the sulphate radical?
A) -2.
B) -1.
C) +1.
D) +2.
Show Answer
Explanations:
The valency of the sulphate radical is -2. This is because in a sulfate ion (SO₄²⁻), sulfur has an oxidation state of +6 and each oxygen atom has an oxidation state of -2, resulting in a total charge of -2 for the sulfate ion.
Option Analysis:
Option A:
Correct. The valency of the sulphate radical is indeed -2.
Option B:
Incorrect. Sulfate does not have a -1 valency.
Option C:
Incorrect. Sulfur in sulfate has an oxidation state of +6, not +1.
Option D:
Incorrect. The overall charge on the sulfate ion is -2, not +2.
5.
What is the electronic configuration of hydrogen according to Bohr's model?
Show Answer
Explanations:
The electronic configuration of hydrogen according to Bohr's model is 1, as hydrogen has one electron that orbits the nucleus in the first energy level.
Option Analysis:
Option A:
Correct. Hydrogen has one electron filling the first and only energy level.
Option B:
Incorrect. Bohr's model does not assign two electrons to hydrogen.
Option C:
Incorrect. There is no fourth energy level for a single-electron atom like hydrogen.
Option D:
Incorrect. Three or more energy levels are not required for hydrogen.
6.
Which of the following elements has a valency of 2?
A) Calcium.
B) Carbon.
C) Oxygen.
D) Iron.
Show Answer
Explanations:
Calcium (Ca) has a valency of 2 because it typically loses two electrons to achieve a stable electron configuration, forming Ca
2+
ions in chemical reactions.
Option Analysis:
Option A:
Correct. Calcium commonly forms +2 ions.
Option B:
Carbon can have multiple valencies (4, 2, or even 3), but not consistently 2.
Option C:
Oxygen usually has a valency of -2, as it gains two electrons to complete its octet.
Option D:
Iron can have various oxidation states (such as +2 and +3), but the most common for forming simple ions is +2 or +3, not consistently 2.
7.
What is the formula of the compound formed between magnesium and oxygen?
A) Mg$_{2}$O.
B) MgO$_{2}$.
C) Mg$_{2}$O$_{2}$.
D) MgO.
Show Answer
Explanations:
The formula for the compound formed between magnesium and oxygen is
MgO
. This follows from the valency rules: Magnesium has a +2 valency, while oxygen typically has a -2 valency. When these two elements combine, their charges balance out to form Mg
1
O
1
, which simplifies to MgO.
Option Analysis:
Option A:
Incorrect; it suggests an incorrect stoichiometry for oxygen.
Option B:
Incorrect; it suggests an incorrect stoichiometry for magnesium and oxygen.
Option C:
Incorrect; it suggests a peroxide compound, which is not formed between these elements under normal conditions.
Option D:
Correct; it accurately represents the formula of magnesium oxide based on their valencies.
8.
The electronic configuration of Neon is
A) 2, 7.
B) 2, 8, 8.
C) 2, 6.
D) 2, 8.
Show Answer
Explanations:
The correct answer is D) 2, 8. Neon has an atomic number of 10, meaning it has 10 electrons in its neutral state. The electron configuration follows the Aufbau principle, filling orbitals starting from the lowest energy level to the highest. For Neon, this results in two electrons in the first shell (2s
2
) and eight electrons in the second shell (2p
6
), totaling 10 electrons.
Option Analysis:
Option A:
Incorrect. It suggests only 9 electrons, which is not correct for Neon.
Option B:
Incorrect. This option incorrectly splits the second shell into two groups of eight, which is not possible in electron configuration notation.
Option C:
Incorrect. It suggests only 8 electrons, missing one electron from the actual count for Neon.
Option D:
Correct. This accurately represents the 10 electrons in Neon's electron configuration as described above.
9.
Magnesium ion (Select the correct charge)
A) +1.
B) +2.
C) +3.
D) None of the above.
Show Answer
Explanations:
Magnesium (Mg) is a Group 2 element in the periodic table, which means it typically forms ions with a +2 charge by losing two electrons.
Option Analysis:
Option A:
Incorrect. Magnesium does not form a +1 ion.
Option B:
Correct. Magnesium forms a +2 ion, which is consistent with its position in Group 2 of the periodic table.
Option C:
Incorrect. Magnesium does not form a +3 ion.
Option D:
Incorrect. There is a correct answer among the options provided.
10.
What is the valency of Iron in its ferrous form?
Show Answer
Explanations:
The valency of iron in its ferrous form (Fe
2+
) is 2. This is because the iron atom has lost two electrons, resulting in a +2 charge, which indicates it can form two bonds or connections with other atoms.
Option Analysis:
Option A:
Incorrect. Valency of Fe
2+
is not 4.
Option B:
Correct. Valency of Fe
2+
is 2, as it has a +2 charge.
Option C:
Incorrect. Valency of Fe
2+
is not 1.
Option D:
Incorrect. Valency of Fe
2+
is not 3.
11.
Which of the following is a movalent cation?
A) Manganous.
B) Stannous.
C) Ferrous.
D) Cuprous.
Show Answer
Explanations:
Cuprous is a correct answer because it refers to the copper ion with a +1 charge, making it a monovalent cation.
Option Analysis:
Option A:
Manganous typically denotes manganate or permanganate ions, not a single positive charge.
Option B:
Stannous refers to tin with a +2 charge, making it divalent, not monovalent.
Option C:
Ferrous indicates iron with a +2 charge, also divalent, not monovalent.
Option D:
Cuprous is correct as it denotes copper with a +1 charge, making it monovalent.
12.
Sodium chloride formula is
A) NaCl$_{2}$.
B) Na(Cl)$_{2}$.
C) NaCl.
D) Na2Cl$_{2}$.
Show Answer
Explanations:
The correct formula for sodium chloride is
Option C: NaCl.
Sodium (Na) has a valency of +1, and chlorine (Cl) has a valency of -1. These ions combine in a 1:1 ratio to form an ionic compound with no additional subscripts needed.
Option Analysis:
Option A:
Incorrect because it suggests sodium chloride contains two chloride ions, which is not the case.
Option B:
Incorrect as it implies a complex structure around the chlorine ion that isn't present in NaCl.
Option C:
Correct as it accurately represents the 1:1 ratio of sodium to chloride ions.
Option D:
Incorrect because it suggests an unbalanced formula with two sodium and two chloride ions, which is not correct for NaCl.
13.
If I gain electrons I become
A) Positive because I've added to my atom.
B) Equal because now I have electrons.
C) Same because i'm balanced.
D) Negative because I've added electrons.
Show Answer
Explanations:
Adding electrons to an atom results in a negative charge because electrons carry a negative electrical charge, and the addition of more negatively charged particles makes the overall particle negatively charged.
Option Analysis:
Option A:
Incorrect. Adding electrons does not make something positive; it makes it negatively charged.
Option B:
Incorrect. The term "equal" is not relevant to the charge change when adding electrons.
Option C:
Incorrect. Being balanced does not apply to electrical charges in this context.
Option D:
Correct. Adding electrons results in a negative charge due to the negative nature of electrons.
14.
Ammonium ion (Select the correct charge)
A) +1.
B) +2.
C) +3.
D) None of the above.
Show Answer
Explanations:
Ammonium ion (NH
4
+
) has a +1 charge because it carries one less electron than the number of protons in its nucleus, resulting from the loss of a single hydrogen atom with its electron.
Option Analysis:
Option A:
Correct. Ammonium ion indeed has a +1 charge.
Option B:
Incorrect. Ammonium does not have a +2 charge.
Option C:
Incorrect. Ammonium does not have a +3 charge.
Option D:
Incorrect. There is a correct answer among the options provided.
15.
Valency of bicarbonate is
A) +1.
B) -2.
C) -1.
D) +2.
Show Answer
Explanations:
Valency, in the context of chemistry and not English grammar, refers to the combining power of an atom. For bicarbonate (HCO₃⁻), it has a negative charge of -1 due to the presence of one extra electron or the absence of one proton. This means that bicarbonate can combine with positive ions to form salts.
Option Analysis:
Option A:
Incorrect. Bicarbonate does not have a +1 valency.
Option B:
Incorrect. Bicarbonate has a -2 charge, but its valency is defined by the number of bonds it can form, which in this case is -1 due to its single negative charge.
Option C:
Correct. Bicarbonate has a valency of -1 because it carries one negative unit of charge.
Option D:
Incorrect. Bicarbonate does not have a +2 valency.
16.
Which of the following correctly represents the electronic distribution in the Mg atom? .
A) 2, 8, 2.
B) 1, 8, 3.
C) 3, 8, 1.
D) 8, 2, 2.
Show Answer
Explanations:
The correct answer is
A) 2, 8, 2.
This represents the electron configuration of magnesium (Mg), which has an atomic number of 12. The electron distribution in Mg follows the Aufbau principle: starting from the lowest energy level to the highest, it fills as 2 electrons in the first shell, 8 in the second shell, and 2 in the third shell.
Option Analysis:
Option A:
Correct. Represents 12 electrons distributed according to electron shells.
Option B:
Incorrect. Misplaced number of electrons per shell.
Option C:
Incorrect. Misplaced number of electrons per shell.
Option D:
Incorrect. Misplaced number of electrons per shell.
17.
Valency of an atom definedas
A) No. Of neutrons in an atom.
B) No. of protons in an atom.
C) No.of electrons in the innermost shell.
D) Combining capacity of an atom.
Show Answer
Explanations:
Valency of an atom is defined as the combining capacity of an atom, which refers to its ability to form chemical bonds with other atoms. This directly corresponds to option D.
Option Analysis:
Option A:
No. Of neutrons in an atom - This relates to atomic mass but not valency.
Option B:
No. of protons in an atom - This defines the atomic number and element identity, not valency.
Option C:
No.of electrons in the innermost shell - This is related to electron configuration but not specifically valency.
Option D:
Combining capacity of an atom - Correct. Valency describes how many atoms can bond with it or its bonding capability.
18.
The element with atomic number 9 is .....
A) Neon.
B) Oxygen.
C) Sodium.
D) Fluorine.
Show Answer
Explanations:
Fluorine has an atomic number of 9, making it the correct answer.
Option Analysis:
Option A:
Neon has an atomic number of 10.
Option B:
Oxygen has an atomic number of 8.
Option C:
Sodium has an atomic number of 11.
Option D:
Fluorine indeed has an atomic number of 9, which is correct.
19.
What is the electronic configuration of oxygen?
A) 2.8.1.
B) 2.8.8.1.
C) 2.6.
D) 2.4.
Show Answer
Explanations:
The electronic configuration of oxygen is
2,6.
This means that the first shell (K) has 2 electrons and the second shell (L) has 6 electrons. Oxygen has an atomic number of 8, which means it has a total of 8 electrons distributed in its shells.
Option Analysis:
Option A:
Incorrect as it suggests a configuration with three shells instead of two.
Option B:
Incorrect due to the extra shell and incorrect number of electrons in each shell.
Option C:
Correct. Matches the actual electronic configuration of oxygen.
Option D:
Incorrect as it suggests a configuration with only two shells but an incorrect distribution of electrons.
20.
Same number of protons, different number of neutrons
A) Atomic number.
B) Mass number.
C) Isotope.
D) Ion.
Show Answer
Explanations:
Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons, leading to variations in their mass numbers.
Option Analysis:
Option A:
Atomic number refers to the number of protons and defines the element. Not related to having a different number of neutrons.
Option B:
Mass number is the sum of protons and neutrons, which would be different for isotopes but not directly defining them as such.
Option C:
Isotope correctly describes atoms with the same atomic number (protons) but differing numbers of neutrons.
Option D:
An ion is an atom or molecule that has gained or lost one or more electrons, altering its charge. Not related to having a different number of neutrons while keeping the same number of protons.
21.
Valency of Platinous
A) $Pb^{-2}$.
B) $Pb^{-1}$.
C) $Pt^{+2}$.
D) $Pt^{-2}$.
Show Answer
Explanations:
The valency of platinous is represented by
Option C: $Pt^{+2}$.
Platinum (Pt) typically forms compounds with a +2 charge, indicating its valency in this context.
Option Analysis:
Option A:
Incorrect. Lead ($Pb$) has a -2 valency, not platinum.
Option B:
Incorrect. Lead ($Pb$) has a -1 valency, not platinum.
Option C:
Correct. Platinum (Pt) commonly forms compounds with a +2 charge.
Option D:
Incorrect. Platinum does not form compounds with a -2 charge.
22.
What is the valency of Sodium?
A) 1.
B) 2.
C) 3.
D) None of the above.
Show Answer
Explanations:
Valency, in the context of chemistry, refers to the combining power of an atom as indicated by its number of bonds it can form with other atoms. Sodium (Na) typically forms one ionic bond by losing one electron, making its valency 1.
Option Analysis:
Option A:
Correct. Sodium's valency is 1 because it readily loses one electron to achieve a stable electron configuration.
Option B:
Incorrect. Sodium does not form two bonds in its common ionic compounds.
Option C:
Incorrect. Sodium's valency cannot be 3 as it only needs to lose one electron to become stable.
Option D:
Incorrect. The correct answer is provided by Option A.
23.
Which of the following are ions?
A) Ca$^{2+}$.
B) Cl$^{-}$.
C) CO$_{3}$$^{2-}$.
D) All of the above.
Show Answer
Explanations:
All the given options represent ions:
- Option A, Ca
2+
, is a calcium ion.
- Option B, Cl
-
, is a chloride ion.
- Option C, CO
3
2-
, is a carbonate ion.
Option Analysis:
Option A:
Calcium ion (Ca
2+
) - Positively charged ion.
Option B:
Chloride ion (Cl
-
) - Negatively charged ion.
Option C:
Carbonate ion (CO
3
2-
) - Negatively charged ion.
Option D:
All of the above are ions, thus correct.
24.
How many valence electrons are found in atoms of group 1?
Show Answer
Explanations:
Group 1 elements, also known as alkali metals, have one valence electron in their outermost shell. This is why they readily lose this single electron to achieve a stable electronic configuration similar to that of the nearest noble gas.
Option Analysis:
Option A:
Correct. Alkali metals like lithium (Li), sodium (Na), and potassium (K) all have one valence electron.
Option B:
Incorrect. Seven valence electrons would place these elements in Group 7, not Group 1.
Option C:
Incorrect. Four valence electrons would place these elements in Group 4.
Option D:
Incorrect. Six valence electrons would place these elements in Group 6.
25.
How many Hydrogen are in 4H$_{2}$O?
Show Answer
Explanations:
In the chemical formula for water, H
2
O, each molecule contains two hydrogen atoms. Therefore, in four molecules of water (4H
2
O), there are a total of 8 hydrogen atoms.
Option Analysis:
Option A:
Incorrect because it suggests only 4 hydrogen atoms, which is half the actual number.
Option B:
Incorrect as it indicates only 2 hydrogen atoms, representing a single molecule of water.
Option C:
Correct. Four molecules of H
2
O contain 8 hydrogen atoms in total.
Option D:
Incorrect because it implies there are 6 hydrogen atoms, which is not the case for four water molecules.
26.
Valency of Ferrous
Show Answer
Explanations:
Valency in chemistry refers to the number of hydrogen atoms that an element can combine with, or equivalently, the number of electrons it can lose, gain, or share in order to form chemical bonds. For ferrous (Fe
2+
), which is iron in its +2 oxidation state, it typically forms two bonds.
Option Analysis:
Option A:
Correct. Ferrous has a valency of 2.
Option B:
Incorrect. Valency is not 4 for ferrous.
Option C:
Incorrect. Valency is not 3 for ferrous.
Option D:
Incorrect. Valency is not 1 for ferrous.
27.
The charge on any ion would depend on loss or gain of .....
A) Electrons.
B) Protons.
C) Positrons.
D) Neutrons.
Show Answer
Explanations:
The charge on any ion would depend on the loss or gain of electrons. Electrons carry a negative charge, and when an atom gains or loses electrons, it results in a positively or negatively charged ion, respectively.
Option Analysis:
Option A:
Correct. Electrons determine the charge of ions through their gain or loss.
Option B:
Incorrect. Protons are part of the nucleus and do not directly affect an ion's charge in terms of gaining or losing particles.
Option C:
Incorrect. Positrons, being the antimatter counterpart to electrons, are not typically involved in the formation of ions through common chemical processes.
Option D:
Incorrect. Neutrons do not affect an ion's charge as they have no electric charge themselves.
28.
Valency of "Silicon"
A) $2$.
B) $3^+$.
C) $1^-$.
D) $4$.
Show Answer
Explanations:
Silicon has a valency of 4, which means it can form four covalent bonds with other atoms. This is due to its position in group 14 (IV A) of the periodic table, where the number of valence electrons equals the group number.
Option Analysis:
Option A:
Incorrect. Silicon does not typically form two covalent bonds.
Option B:
Incorrect. The +3 charge is not a valency but an oxidation state, which silicon rarely achieves in compounds.
Option C:
Incorrect. Silicon cannot have a -1 charge as it does not gain three electrons to achieve a stable electron configuration.
Option D:
Correct. Silicon's position in the periodic table and its ability to form four covalent bonds confirm this valency.
29.
What is the valency of Phosphate?
A) +3.
B) -3.
C) -2.
D) -1.
Show Answer
Explanations:
Phosphate has a valency of -3 because it typically forms compounds where the phosphate ion (PO
4
3-
) carries three negative charges. This is due to the oxygen atoms in the phosphate ion having a higher electronegativity than phosphorus, leading to an overall negative charge.
Option Analysis:
Option A:
Incorrect. Phosphate does not have a +3 valency.
Option B:
Correct. Phosphate has a -3 valency as it forms compounds with three negative charges.
Option C:
Incorrect. Phosphate is not known to form compounds where the ion carries two negative charges in its standard state.
Option D:
Incorrect. Phosphate does not have a -1 valency; it has a -3 valency.
30.
What is the valency of Calcium (Ca)
Show Answer
Explanations:
Calcium (Ca) is a metal and typically forms +2 ions in chemical reactions, making its valency 2. This is consistent with the charge on calcium ions observed in compounds like calcium chloride (CaCl₂).
Option Analysis:
Option A:
Incorrect. Valency of 4 is not typical for calcium.
Option B:
Correct. Calcium's valency is +2, as it commonly forms Ca²⁺ ions in compounds.
Option C:
Incorrect. Valency of 1 is not characteristic of calcium behavior.
Option D:
Incorrect. Valency of 3 is not observed for calcium in its common chemical reactions.
Frequently Asked Questions
What is valency in the context of chemical bonding?
Valency refers to the number of electrons an atom can lose, gain, or share to form chemical bonds with other atoms. It determines the combining capacity of elements and their ability to participate in chemical reactions.
How does valency affect the formation of ionic compounds?
Valency influences the charge an atom can carry, which is crucial for forming ionic bonds. Atoms with a higher valency tend to form more complex ionic structures by exchanging electrons to achieve a stable electron configuration.
Can you explain the concept of monovalent cations?
Mondivalent cations are ions that have a single positive charge, meaning they lose one electron to achieve a stable configuration. Examples include alkali metals like sodium (Na+).
What role does valency play in understanding the structure of chemical compounds?
Valency helps predict how atoms will bond to form molecules and compounds. By knowing the valencies of elements, chemists can determine possible bonding patterns and molecular structures.
How is valency determined for an element?
Valency is typically determined by the number of electrons in the outermost shell (valence shell) of an atom, which influences its ability to form bonds. This can be understood through the electron configuration or atomic number of the element.