Chemistry MCQs
Topic Notes: Chemistry
MCQs and preparation resources for competitive exams, covering important concepts, past papers, and detailed explanations.
Plato
- Biography: Ancient Greek philosopher (427–347 BCE), student of Socrates and teacher of Aristotle, founder of the Academy in Athens.
- Important Ideas:
- Theory of Forms
- Philosopher-King
- Ideal State
31
What is the fundamental reason that elements within the same group exhibit similar chemical behavior?
Answer:
They have the same electronic configuration
Elements in the same group have the same number of valence electrons in their outer shell, which results in a similar valence shell electronic configuration. Since the chemical properties of an element are largely dictated by its valence electrons, elements with identical valence configurations behave similarly in chemical bonding and reactions.
32
In the periodic table, which element exhibits a diagonal relationship with aluminium?
Answer:
beryllium
A diagonal relationship exists between certain elements of the second and third periods. Aluminium (Period 3, Group 13) shows similar chemical properties to Beryllium (Period 2, Group 2) due to their similar charge-to-size ratios, which is a classic example of diagonal similarity.
33
How does the number of valence electrons change as you move down a group in the periodic table?
Answer:
remains the same
Elements within the same group of the periodic table possess the same number of valence electrons in their outermost shell. This similarity in valence electron configuration is the primary reason why elements in the same group exhibit similar chemical properties.
34
What do elements in the same group of the modern periodic table have in common regarding their atomic structure?
Answer:
same electron number in outer cell
Elements within the same group of the modern periodic table share the same number of valence electrons (electrons in the outermost shell). This similarity in valence electron configuration is the primary reason why elements in the same group exhibit similar chemical properties.
35
An element has an electronic configuration of 2, 8, 6. To which group and period does it belong?
Answer:
Group 16 and Period 3
The configuration 2, 8, 6 indicates three occupied electron shells, placing the element in Period 3. The valence shell contains 6 electrons. For p-block elements, the group number is calculated as 10 + valence electrons, which is 10 + 6 = 16. Thus, it is in Group 16.
36
Which characteristic is primarily responsible for the similar chemical properties observed among elements within the same group of the periodic table?
Answer:
Number of valence electrons
Elements in the same group of the periodic table exhibit similar chemical properties because they possess the same number of valence electrons. Since chemical reactions primarily involve the interaction of valence electrons, elements with identical valence configurations tend to form similar types of bonds and compounds.
37
Elements that share the same outer shell electronic configuration are organized into which of the following structures?
Answer:
All of these
In the periodic table, elements with identical valence electron configurations are grouped together. These are referred to as groups, vertical columns, or chemical families, as they exhibit similar chemical properties due to their shared electronic structure in the outermost shell.
38
Match the following properties with their representative elements: (a) Recently named by IUPAC, (b) Variable valency, (c) Maximum electronegativity, (d) Maximum electron affinity.
Answer:
a-2, b-1, c-4, d-3
Based on standard chemical properties: (a) Recently named (e.g., Copernicium), (b) Iron (variable valency), (c) Fluorine (max electronegativity), (d) Chlorine (max electron affinity). The mapping aligns with option D.
39
Which of the following pairs of elements is listed in the correct order of increasing atomic number when moving from left to right across the periodic table?
Answer:
Be, B
Atomic number increases as you move from left to right across a period. Beryllium (Be) has an atomic number of 4, and Boron (B) has an atomic number of 5. Therefore, the sequence Be, B represents an increase in atomic number. The other options (Ca=20, Cl=17; Na=11, Ne=10; He=2, H=1) show a decrease in atomic number.
40
Match the following properties with the correct elements: (a) Most reactive alkali metal, (b) Chemically most active non-metal, (c) Metal with maximum density, (d) Transition metal in liquid state.
Answer:
a-2, b-1, c-4, d-3
Cesium (Cs) is the most reactive alkali metal. Fluorine (F) is the most reactive non-metal. Osmium (Os) has the highest density among metals. Mercury (Hg) is the only transition metal that is liquid at room temperature. Thus, the correct mapping is a-2, b-1, c-4, d-3.