Class 10 Science Chapter 5 MCQ

Here, all the statements are correct. Hence, your answer will be option [D].

Here, all the statements are incorrect. Hence, your answer will be option [D]. Explanation: In option [A], In Mendeleev’s periodic table, the elements are arranged on the basis of their atomic masses and also on the similarity of chemical properties, whereas the modern periodic table is based on the atomic numbers of elements. In option [B]: Dobereiner’s triads also exist in the columns of Newlands’ classification of elements based on the law of octaves. In option [C]: The periodic table is a chart of elements prepared in such a way that the elements having similar properties occur in the same vertical column or group. It is called periodic because the elements having similar properties are repeated after certain intervals or periods; and it is called a table because the elements are arranged in the tabular form.

Due to large positive charge on the nucleus, the electrons are pulled in more close to the nucleus and the size of the atom decreases. However, the size of atom of an inert gas is bigger than that of the preceding halogen atom. The greater size of the inert gas atom in a period is due to the structural stability of its outermost shell consisting of an octet of electrons. Note: As we move from left to right in a period, the atomic number of elements increases which means that the number of protons and electrons in the atoms increases (the extra electrons being added to the same shell.

The first period starts with hydrogen and ends with noble gas helium. All other periods start with alkali metals like lithium, sodium, potassium, etc., and end with noble gases like neon, argon, krypton, etc.

In the modern periodic law, the electronic configuration of silicon is 2, 8, 4.

Na and K are in the same group and K is below than Na, so K will have higher atomic radius i.e., K > Na. In a period on moving from left to right, atomic radius decreases. Since, K and Ca are in the same period and K is in 1 group and Ca is in 2 group, so atomic radius of K will be more than Ca, i.e., K> Ca. Also, Na and Mg are in the same period, but Na belongs to 1 group and Mg belongs to 2 group, so atomic radius of Na is more than Mg, i.e., Na > Mg. Thus, if we take all these together we get K > Na > Mg and K > Ca> Mg. Hence, we can say the atomic radius of K largest. Note: Atomic radii increases on moving down the group as new shell of electrons is added at each succeeding element.

Electronic configuration of A (atomic number 9) is 2, 7. Electronic configuration of B (atomic number 11) is 2, 8, 1. Electronic configuration of C (atomic number 17) is 2, 8, 7. Electronic configuration of D (atomic number 12) is 2, 8, 2. Electronic configuration of E (atomic number 13) is 2, 8, 3. Elements which differ in atomic number by 8 i.e., 9 (A fluorine) and 17 (Cl chlorine) lie in the same group i.e., group 17 (halogens).

Modern Periodic table has 18 vertical columns, known as groups and 7 horizontal rows, known as periods.

Here, all the statements are correct. Hence, your answer will be option [D].

All the elements in the modern periodic table are arranged on the basis of their increasing atomic number. All the isotopes can be placed at one place in the same group of the periodic table. Note: In the modern periodic table or in the long form of the periodic table, the elements are arranged in increasing order of their atomic numbers. This table was prepared by Bohr and is based upon the electronic configuration of elements.