Which of the following statements is correct?
Atomic size decreases down the group
Atomic size increases across the period
Anions are smaller than the parent atom
Cations are smaller than the parent atom
Correct answer is D
A cation is a positively charged ion. This means electron is given out by a cation, hence the cation is smaller than the parent atom.
An atom of an element X gains two electrons. The symbol of the ion formed is
X +
X 2+
X 2-
X -
Correct answer is C
X gained two electrons. X = 2-.
The ion formed is X\(^{2-}\).
The formula of the compound formed between a trivalent metal, M and a divalent non-metal, Y is
M2Y3
M3Y2
MY
M3Y
Correct answer is A
M is a trivalent metal i.e M = 3+ ; Y is a divalent non-metal i.e Y = 2-
A reaction between M and Y will yield M\(_2\)Y\(_3\).
The molecule which has a linear shape is
CH4
NH3
H2S
CO2
Correct answer is D
The shapes of the molecules are:
CH\(_4\) - Tetrahedral; NH\(_3\) - Trigonal pyramidal; H\(_2\)S - Bent; C)\(_2\) - Linear.
Which of the following instruments is used in detecting the presence of radiation?
Cathode ray tube
Geiger-Muller counter
Mass spectrometer
X-ray tube
Correct answer is B
The Geiger- Muller counter is a device for measuring radioactivity by detecting and counting ionizing particles.