1.
Which of the following is false?
Correct Answer
B. Covalent bond be between two metals
Explanation
The correct answer is "covalent bond be between two metals" because a covalent bond is formed when two atoms share electrons. Covalent bonds typically occur between nonmetals or between a nonmetal and a metalloid, but not between two metals. Metals tend to form metallic bonds, where the valence electrons are delocalized and shared among all the atoms in the metal lattice.
2.
How many single covalent bonds must a carbon atom form to have eight electrons in the outer shell?
Correct Answer
C. 4
Explanation
A carbon atom has four valence electrons, and it needs a total of eight electrons in its outer shell to achieve stability. To do this, it must form four single covalent bonds with other atoms, as each bond involves sharing one electron. Therefore, the correct answer is 4.
3.
All of the Nobel gas have eight electrons in the outer shell except:
Correct Answer
B. He
Explanation
All of the Nobel gases have eight electrons in their outer shell except for helium (He). Helium only has two electrons in its outer shell. This is because helium is the first element in the periodic table and has only one energy level, which can hold a maximum of two electrons. Therefore, it does not follow the octet rule like the other Nobel gases, which have multiple energy levels and can hold up to eight electrons in their outer shell.
4.
How many bonds do they form the ( N, O, H, C) respectively?
Correct Answer
A. 3,2,1,4
Explanation
The correct answer is 3,2,1,4. This answer indicates the number of bonds formed by each element in the given sequence (N, O, H, C). N forms 3 bonds, O forms 2 bonds, H forms 1 bond, and C forms 4 bonds.
5.
What type of covalent bond between two atoms of nitrogen?
Correct Answer
B. Trouble bond
6.
When the distance between the atoms decreases, the lattice energy is increase.
Correct Answer
A. True
Explanation
When the distance between atoms in a lattice decreases, the lattice energy increases. This is because lattice energy is the energy required to separate the atoms in a crystal lattice, and as the distance between the atoms decreases, it becomes more difficult to separate them. Therefore, the lattice energy increases as the distance decreases.
7.
Which of the following bonds would be the largest polar?
Correct Answer
A. C-F
Explanation
The bond between carbon and fluorine (C-F) would be the largest polar because fluorine is the most electronegative element on the periodic table. Electronegativity is a measure of an atom's ability to attract electrons towards itself in a chemical bond. Since fluorine has a higher electronegativity than carbon, it will pull the shared electrons in the bond closer to itself, creating a partial negative charge on the fluorine atom and a partial positive charge on the carbon atom. This unequal sharing of electrons results in a larger separation of charge, making the C-F bond the most polar.
8.
Which of the bonds have electronegativity equal zero:
Correct Answer
C. Non polar covalent bond
Explanation
A nonpolar covalent bond occurs when the electronegativity difference between two atoms is very small or zero. In this type of bond, the electrons are shared equally between the atoms, resulting in a balanced distribution of charge. Therefore, the correct answer is "Non polar covalent bond" as it has an electronegativity equal to zero.
9.
Radius increase from right to left and decrease from bottom to top in the periodic table.
Correct Answer
A. True
Explanation
The statement is true because the periodic table is organized based on the atomic number of elements, which increases from left to right and from top to bottom. The atomic number is directly related to the number of protons in an atom's nucleus, and as the number of protons increases, so does the size of the atom's electron cloud. Therefore, as we move from right to left in a period (horizontal row) of the periodic table, the radius of the atoms increases. Similarly, as we move from top to bottom in a group (vertical column), the radius also increases due to the addition of more energy levels or shells.
10.
Which of the following relations is false?
Correct Answer
D. Number of covalent bond increase , strength of the bond decrease
Explanation
Increasing the number of covalent bonds actually increases the strength of the bond. This is because each covalent bond involves the sharing of electrons between atoms, creating a strong attraction between the atoms. Therefore, the statement "Number of covalent bond increase, strength of the bond decrease" is false.
11.
Which of the following form a covalent bond?
Correct Answer
D. All of the above
Explanation
All of the given compounds, CH4, NH3, and H2O, form covalent bonds. Covalent bonds occur when two atoms share electrons in order to achieve a stable electron configuration. In CH4, carbon shares its electrons with four hydrogen atoms, forming four covalent bonds. In NH3, nitrogen shares its electrons with three hydrogen atoms, forming three covalent bonds. In H2O, oxygen shares its electrons with two hydrogen atoms, forming two covalent bonds. Therefore, all of the compounds listed form covalent bonds.
12.
Arrange of the following atom to increase lattic energy :
KCl , MgO , AlCl3 , KBr
Correct Answer
C. KBr < KCl < AlCl3 < MgO
Explanation
The correct answer is KBr < KCl < AlCl3 < MgO. Lattice energy is the energy released when gaseous ions come together to form a solid lattice. It is directly proportional to the charges of the ions and inversely proportional to the distance between them. In this case, KBr has the highest lattice energy because both K+ and Br- ions have larger charges compared to the other ions. KCl has the next highest lattice energy because it also has ions with large charges. AlCl3 has lower lattice energy because it has a smaller charge on the Al3+ ion. MgO has the lowest lattice energy because it has ions with the smallest charges.
13.
Which of the following atoms have the highest polarity?
Correct Answer
B. F
Explanation
Fluorine (F) has the highest polarity among the given atoms. Polarity is determined by the electronegativity difference between atoms in a chemical bond. Fluorine has the highest electronegativity value (3.98) on the Pauling scale, indicating its strong ability to attract electrons towards itself. This high electronegativity results in a large electronegativity difference when fluorine is bonded with other atoms, leading to a highly polar bond. Therefore, F has the highest polarity among C, F, H, and O.
14.
Which of the following is true about of " double bond"?
Correct Answer
C. Two pairs of electron shared
Explanation
A double bond is formed when two pairs of electrons are shared between two atoms. In a double bond, each atom contributes one electron from a different orbital, resulting in a total of four electrons being shared. This sharing of electrons creates a strong bond between the atoms, making the molecule more stable. Therefore, the correct answer is "Two pairs of electron shared."
15.
Which of the following has the largest radius?
Correct Answer
D. CaS
Explanation
CaS has the largest radius among the given options. This is because as we move down a group in the periodic table, the atomic radius increases. Both Mg and Ca belong to the same group (Group 2), but Ca is lower in the group than Mg. Similarly, both O and S belong to the same period (Period 2), but S is lower in the period than O. Therefore, CaS has a larger radius compared to MgO, MgS, and CaO.